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Palaeontology
VOLUME 23 ■ PART 3 AUGUST 1980
Published by
The Palaeontological Association London
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24. (for 1980): Dinoflagellate Cysts and Acritarchs from the Eocene of southern England, by j. b. bujak, C. downie, g. l. eaton, and G. l. williams. 104 pp., 24 text-figs., 22 plates. Price £15 (U.S. $36).
© The Palaeontological Association, 1980
Cover: Edriophus levis (Bather, 1914) from the Middle Ordovician Trenton Group of Kirkfield, Ontario. x2-5. Specimen in the Smithsonian Institution; photograph by H. B. Whittington.
DINOFLAGELLATE CYSTS FROM THE UPPER EOCENE-LOWER OLIGOCENE OF THE ISLE OF WIGHT
by M. LIENGJARERN, L. COSTA, and C. DOWNIE
Abstract. The Upper Eocene and Oligocene succession of the Isle of Wight, southern England (Headon Beds to Hamstead Beds) has been studied palynologically. Seventy-one forms of dinoflagellate cysts are recorded, including two new genera, Gerdiocysta and Vectidinium, and ten new species, Distatodinium scariosum, Eocladopyxis tessellata, G. conopeum, Glaphyrocysta paupercula , Phelodinium pachyceras, P. pumilum, Phthano- peridinium amiculum, P.flebile, Thalassiphora fenestrata, and V. stover i. The dinoflagellates (with the exception of Vectidinium) are marine and indicate six marine incursions or partial incursions in the sequence; the mid- Headon Beds, the Oyster Bed of the Bembridge Marls, the Nematura Band, and three episodes of the Upper Hamstead Beds. Correlation with the Paris Basin indicates that the base of the Stampian lies near the Nematura Band.
The importance of dinoflagellate cysts in the stratigraphy of the Palaeogene has been emphasized in several recent papers. Many long-standing problems in the Upper Palaeocene and Lower Eocene have been resolved by their application, but problems of correlation at the Eocene/Oligocene boundary remain. This account describes the dinoflagellate cysts from the classical section on the Isle of Wight in southern England. The initial work was done by M. Liengjarern (1973) and has been revised recently by L. Costa.
STRATIGRAPHY
The sequences in the Isle of Wight span the Eocene/Oligocene boundary, and the placings of this boundary have varied according to the interpretation of different authors (see Curry et al. 1978) from the base of the Headon Beds to the base of the Hamstead Beds. The difficulties in correlation and interpretation are largely the consequence of the paralic nature of the deposits, which varied from open-sea to freshwater lacustrine in a complex coastal geography.
Two main localities are reported here. In the east of the island, the lower part of the succession, from the base of the Lower Headon Beds to the Bembridge Marls, is exposed continuously in the sea cliffs at WhitecliffBay. In the west, the upper part of the succession (Bembridge Marls-Hamstead Beds) is exposed in Bouldnor and Hamstead cliffs as a continuous sequence (text-figs. 1 and 2).
PALYNOLOGY
All the samples were prepared by standard palynological methods. Only a few samples of fluvial sands were barren, the remainder yielded rich assemblages of palynomorphs, including pollen and spores, plant tissue, freshwater algae, dinoflagellate cysts, and acritarchs. Only the dinoflagellate cysts are dealt with in detail in this paper, but in each sample the proportions of pollen and spores, Pediastrum, dinoflagellates, and acritarchs based on counts of 200 individuals were noted. These results are shown in Tables 1 and 2. It should be noted that these counts were made after sieving through a 20 ^m sieve and that consequently pollen is under- represented.
A complete list of the dinoflagellate taxa recorded and their distribution and relative abundances are shown in Table 1 . Only new taxa or combinations, or taxa necessitating further comment are described here. The genera discussed are arranged in alphabetical order; suprageneric dinoflagellate cyst-taxa are not employed here. (Palaeontology, Vol. 23, Part 3, 1980, pp. 475-499, pis. 53-54.1
476
PALAEONTOLOGY, VOLUME 23
text-fig. 1. Stratigraphic location of samples collected at Hamstead Cliff (prefix H) and at Bouldnor Cliff
(prefix B).
The terms employed in the descriptions are those of Williams et al. (1973) and Evitt et al. (1977). In some species, the arithmetical mean of the measurements is indicated as a figure in parenthesis. The reference for holotypes and illustrated specimens is given with reference to their location in the ‘England Finder’ grid system.
Division pyrrhophyta Class DINOPHYCEAE Fritsch 1935 Order peridiniales Haeckel 1894 Genus distatodinium Eaton 1976
Type species. Distatodinium craterum Eaton 1976
LIENGJARERN ET AL .: EOCENE/OLIGOCENE DINOFL AGELL ATES
477
Distatodinium scariosum sp. nov. Plate 54, fig. 3
Name derivation. Latin, scariosus, thin, papery.
Diagnosis. Distatodinium with broad, hollow, intratabular processes (usually one per paraplate), oblate to subtriangular in cross-section, distally expanded, and bearing a variable number of thick secae on their distal margin. Cingular area devoid of processes.
Description. The central body ambitus is oval, antero-posteriorly elongate. Apex and antapex are rounded; the antapex may be prolonged into a corona formed by the expanded bases of the antapical processes.
The insertion of the processes on the central body is subcircular, oblate, or triangular. The processes occur one per paraplate, except on the antapical paraplate (l'"'), where there may be two or more processes. The degree of compression of the processes varies on a single specimen; some processes are taeniate, but more commonly they are oblate to subtriangular and are open distally. The distal margin of the processes extends into a variable number of robust secae, sometimes prolonged into fine strands which might connect with those from near-by processes.
Two of the apical processes are considerably smaller than the other two. Cingular and sulcal zones are free of processes. When more than one antapical process occurs, their proximal sections coalesce, forming a corona which is apparently hollow.
Holotype. Slide ML 1456, R37/0, sample B 1 1 , Upper Hamstead Beds, Lower Oligocene, Bouldnor Cliff, Isle of Wight.
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Lower
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-WC24
-WC21
WC16 WC15
Brockenhurst Bed
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Bembridge
Limestone
text-fig. 2. Stratigraphic location of samples collected at Whitecliff Bay (prefix WC).
table 1. Distribution of dinoflagellate species
478
PALAEONTOLOGY, VOLUME 23
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PLATE 53
liengjarern et a!., Eocene/Oligocene dinoflagellates
LIENGJARERN ET AL EOCENE/OLIGOCENE DINOFL AGELL ATES
Measurements. Holotype, central body length 51 ju.m including operculum (43 not including operculum), breadth 31 /urn; process length 5-15-5 /nm.
Range. Central body length 38-49 p.m (not including operculum), breadth 26-31 /urn; process length 5-16 y.m. Specimens measured— 8.
Comparisons. The broad, usually hollow and distally open processes, commonly unconnected distally, distinguish D. scariosum from other species in the genus.
Distribution. Samples Bll, B15.
Genus emslandia Gerlach 1961 Type species. Emslandia emslandensis Gerlach 1961
Emslandia sp.
Plate 54, fig. 5
Remarks. This species of Emslandia has a bulging ventral hypocyst surface. The ambitus is sub- circular to ovoid. The epicyst is distally rounded and is prolonged into a very short apical horn, subrectangular in outline, with distal ending truncate, bifid or sometimes produced into a variable number of short solid processes. The hypocyst may be rounded or somewhat pointed medially (?compression) and sometimes bears a very short, solid antapical projection.
The autophragm is robust but does not exceed 2 ^m in thickness, it is apparently spongy, perforate, and its outer surface is scabrate. Linear thickenings of the wall appear scattered randomly on the autocyst; sometimes these coalesce on portions of the cyst producing irregular reticulate structures. Two parallel thickenings of the autophragm mark the cingular margins.
The archeopyle is large, type P. The operculum may remain attached along its cingular suture. Emslandia sp. differs from E. emslandensis by its thinner autophragm and randomly scattered ornament of linear thickenings, in part reticulate. It is clearly a distinct species, but the material is too badly preserved to provide satisfactory types.
Distribution. Samples WC 19-21, 23; Middle Headon Beds, Whitecliff Bay, Isle of Wight.
Genus eocladopyxis Morgenroth 19666 Type species. Eocladopyxis peniculata Morgenroth 19666
Eocladopyxis tessellata sp. nov.
Plate 53, fig. 6
Name derivation. Latin, tessellatum, tessellated.
Diagnosis. Eocladopyxis distinguished by abundant, long, solid, intratabular processes which end distally in fine spines repeatedly furcated and reflexed. The central body is moderately compressed dorso-ventrally and its ambitus is circular. Archeopyle type A + 3A + 6P. Additional sutures may occur randomly between any pair of paraplates.
EXPLANATION OF PLATE 53
Fig. 1. Gerdiocysta conopeum gen. et sp. nov., SEM showing the membrane connecting the distal ends of the processes, x785.
Fig. 2. Gerdiocysta conopeum gen. et sp. nov., holotype, dorsal view showing apical archaeopyle, x 500.
Fig. 3. Glaphyrocysta paupercula sp. nov., holotype, x 1000.
Fig. 4. Phthanoperidinium amiculum sp. nov., holotype, x 1000.
Fig. 5. Glaphyrocysta paupercula sp. nov., specimen with reduced processes, x 1000.
Fig. 6. Eocladopyxis tessellata sp. nov., holotype, x 1000.
482
PALAEONTOLOGY, VOLUME 23
Description. The autocyst is moderately to strongly compressed dorso-ventrally with a circular ambitus. The autophragm is scabrate and is produced into solid intratabular processes, two to four, sometimes more, per paraplate. The processes are only slightly flexible, simple, somewhat expanded proximally, circular in cross- section; distally they flare into a number of fine spines which fork repeatedly; more rarely some of the processes may end in simple bifurcations. They are more or less strongly reflexed.
The archeopyle appears to be of the type A + 3A + 6P although it is possible that all apical plates separate in the formation of the archeopyle. Additional sutures commonly develop, apparently at random, between any other pair of paraplates, both on the epicyst and on the hypocyst.
The paratabulation formula may sometimes be determined on the basis of plate separation, and is 4', 6", 6c, ?5", 1 p.v., 1 " ", ?Xs. Two of the apical paraplates appear to be larger than the other two. The precingular paraplates are of roughly the same size, antero-posteriorly elongate, and pentagonal in outline. The cingular paraplates are narrow and subrectangular, and frequently bear only two processes each. The hypocyst appears to be formed by five large postcingular paraplates, a prominent posterior-ventral paraplate and an antapical paraplate, but these are only rarely evident since secondary sutures are uncommon on the hypocyst; a number of smaller sulcal paraplates also appear to be present.
Holotype. Slide ML 1451, T51/2, sample WC25, Middle Headon Beds, Upper Eocene, Whitecliff Bay, Isle of Wight.
Measurements. Holotype, central body diameter, 37/xm; process length 8-15 /xm.
Range. Central body diameters 31-39 x 35-43 /xm; process length 4-5-10 /xm. Specimens measured— 11.
Comparisons. The solid processes, paratabulation, and archeopyle type leave no doubt as to the generic allocation of E. tessellata-, however, the archeopyle is not always observable, in which case the specimens closely resemble some species of the genus Impletosphaeridium Morgenroth 19666.
E. tessellata differs from E. peniculata Morgenroth, the only other species so far allocated to the genus, in its larger size and longer processes. The process terminations in E. tessellata are more complex than in E. peniculata.
Genus gerdiocysta gen. nov.
Name derivation. Latin, gerdius, weaver.
Type species. Gerdiocysta conopeum sp. nov.
Diagnosis. Cyst ambitus subcircular, posteriorly bilobed or rounded; dorso-ventral compression moderate to strong. Pericyst bearing solid penitabular to intratabular processes arranged into annular, soleate, or linear complexes. The process complexes support a reticulate or membraneous ectophragm, which on the dorsal face and laterally simulate the outline of the paraplates. On the ventral face, a median area of variable size is free of ornament and ectophragm. The processes on either side tend to be linearly oriented more or less parallel to the ambitus; the ectophragm on the ventral face may link processes from different paraplates.
Inferred tabulation formula: 4', 6", 6c, 5'", 1 p.v., 1" ", Os.
Archeopyle type A, with zig-zag margins including a slightly offset sulcal notch. Operculum tetra- tabular, commonly free.
Comments. Gerdiocysta is similar to Areoligera Lejeune-Carpentier but differs strongly in the posses- sion of an ectophragm, which, on parts or all of the dorsal surface of the cyst, simulates the shape of paraplates. In Areoligera the processes may be joined distally or laterally by trabeculae, but these are sparse and are loosely interconnected and do not constitute an outer reticulum or membrane.
The genus Riculacysta Stover 1977, resembles Gerdiocysta in shape and in possessing a membranous perforate to reticulate ectophragm. However, in Riculacysta the processes are not in complexes, and are restricted to the ventro-lateral and lateral zones of the cyst. The ectophragm on the dorsal surface of Riculacysta lies very close to or touches the autophragm and extends across the paraplate sutures in that region. In contrast there are the simulate dorsal complexes in Gerdiocysta.
LIENGJARERN ET AL EOCENE/OLIGOCENE DINOFL AGELL ATES
483
Gerdiocysta conopeum sp. nov.
Plate 53, figs. 1, 2
Derivation of name. Latin, conopeum, mosquito net.
Diagnosis. Gerdiocysta characterized by a finely reticulate to membranous perforate simulate ecto- phragm developed over paraplates V-4', l"-5", 2" '-4'", 1 p.v., and \""\ an arcuate to soleate complex of very reduced processes, distally free, may be developed on paraplate 6". The process bases are connected by microgranular thickenings of the cyst wall which form low ridges within the complexes; these thickenings are often further developed into an intratabular irregular, coarse reticulum. Individual processes are solid, slightly fibrous, and distally furcated. The median ventral area is large.
Description. The antapical bilobation of the central body may be moderately or only weakly marked. The dorsal convexity and ventral depression are moderate. The endophragm is finely granulose, apparently perforate. The periphragm, as seen on the process walls is slightly fibrous.
The process complexes are determined proximally by basal granulose thickenings on the cyst wall, which form a more or less continuous basal ridge. Distally, the simulate ectophragm is well developed over paraplates l'-4', l"-5", 2" '-4" ', 1 p.v., and 1" ". The cingular paraplates 2c-4c may bear linear complexes of processes which may or may not be distally united. A narrow ectophragm may also be developed on the ventral sur- face, forming an arcuate wing bordering the central area free of ornament. The ectophragm is closely perforate and finely reticulate or membranous; both types may combine in the same species.
On some individuals, the processes are greatly reduced, no ectophragm is developed, but a coarse granulate basal reticulum extends over the dorsal plate surfaces; intermediate forms between these and normal specimens with well-developed processes and ectophragm are common.
Holotype. Slide ML 1456, E 29/2, sample Bll, Upper Hamstead Beds, Lower Oligocene, Bouldnor Cliff, Isle of Wight.
Measurements. Holotype, central body length (operculum not included) 64 jim, breadth 73 /urn, processes height up to 20 /un.
Range. Central body length (operculum not included) 47(54-7)64 fim, breadth 63(68)79 pm, process length 6-23 pm. Specimens measured— 15.
Comparisons. No granulate proximal wall thickenings have been mentioned in the description of the only other species in the genus G. cassicula (Drugg) comb, nov., which also appears to differ from G. conopeum in having considerably longer processes and a more prominently bilobed antapex.
Benedek (1972, pi. 1, figs. 1 1 a-c) illustrated examples as Cyclonephelium pastielsii which appear to be conspecific with G. conopeum.
Distribution. Samples B6, 7, 8, 11, and 15. Also in Lower Lintforter Beds and Ratinger Beds (early Rupelian), Germany and Calcaire de Sannois (early Stampian), France (Chateauneuf, pers. comm.).
Other species allocated to the genus: G. cassicula (Drugg) comb. nov. = Areoligera cassicula Drugg 1 970, p. 8 1 1 , figs. 2b, 3a-b.
Genus glaphyrocysta Stover and Evitt 1978 Type species. Glaphyrocysta retiintexta (Cookson 1975)
Glaphyrocysta pauper cula sp. nov.
Plate 53, figs. 3, 5
Name derivation. Latin, pauperculum, diminutive of pauperculus, poor.
Diagnosis. Central body compressed, ambitus subcircular to quadrangular, with or without antapical indentation. Autophragm microgranular, finely reticulate. Processes developed along a peripheral
484
PALAEONTOLOGY, VOLUME 23
band of varying width, leaving relatively prominent mid-dorsal and mid-ventral areas free. Processes solid, fibrous, simple or bifurcate. The processes may be isolated or arranged into linear, arcuate, soleate, or annular complexes. When in complexes the processes are joined by their expanded proximal parts; a few lateral (rarely distal) trabeculae may occur. The complexes have a ragged appearance distally. Processes from different complexes may be joined by basal ridge and/or medially by sparse trabeculae. Processes may be considerably reduced in number and in size.
Processes may occur on some or all of the paraplates T- 4', l"-5" (rarely on 6"), 1" '-5" ', 1 p.v., and l"".
The archeopyle is apical tetratabular, type A; the operculum may be free or remain attached. The archeopyle suture has a sulcal notch a little offset from the mid-body line.
Description. The central body is moderately to strongly compressed; the ambitus varies from subcircular to quadrangular, the antapex is rounded, somewhat indented or produced into one or two unequal lobes. The autophragm appears microgranular in optical section and is finely reticulate in surface view.
The processes are variable in number, size, and shape, and are developed along an ambital line of variable width. The mid-dorsal and especially the mid-ventral areas are free of ornament and relatively prominent. Individual processes, when well developed, are solid, slightly fibrous (most noticeable at and near the base), slender, simple or bifurcate.
The processes may be isolated, although some alignment may often be evident, or arranged into complexes on parts of the cyst. When in complexes, the processes are joined proximally by low ridges formed by their expanded bases; sparse ribbon-like trabeculae with smooth margins may also occur laterally, and only rarely distally. Processes from different complexes may also be united proximally by ridges and laterally by sparse trabeculae. Process complexes are normally present and better defined on the apical, dorsal precingular, and antapical zones of the cyst.
All apical paraplates bear processes, normally arranged into four or three annular or soleate complexes; when four, two are smaller and tend to coalesce into a single elliptical complex. Linear to arcuate complexes may occur on the precingular paraplates l” -5" (occasionally, processes occur on paraplate 6"). Towards the periphery of the dorsal face (2” and 4") the complexes may be soleate. On the ventral face, linear or somewhat arcuate complexes may be clear but sometimes the peripheral processes may coalesce with those from postcingular paraplates and become part of a more or less continuous complex parallel to the ambitus. On the postcingular paraplates process complexes tend to lose definition and to form a number of lines running antero-posteriorly near the periphery of both dorsal and ventral faces. The posterior ventral processes may join in these lines or be separate as an arcuate complex. A soleate complex is frequently observable on paraplate 1"
These forms with more or less well-defined complexes of well-developed processes constitute one end of the range of variation observed in this species. The other end includes forms with some isolated processes reduced to simple spines scattered along the peripheral and dorsal precingular zones, tending to form two to four loosely defined lines parallel to the cyst ambitus. The variability between both extreme types is continuous in the same assemblage and cannot be applied to further taxonomic division.
The archeopyle is apical, tetratabular; the opercula may be free or may remain in place. A rather shallow sulcal notch, relatively little offset from the mid-cyst line is observable on the archeopyle margin.
Holotype. Slide ML 1455 P44/1, sample B8, Upper Hamstead Beds, Lower Oligocene, Bouldnor Cliff, Isle of Wight.
EXPLANATION OF PLATE 54
Fig. 1. Thalassiphora fenestrata sp. nov., holotype, dorsal view, showing archaeopyle and fenestrations, x 250. Fig. 2. Phelodinium pumilum sp. nov., holotype, dorsal view showing archaeopyle and small cavities at the horns, x 1000.
Fig. 3. Distatodinium scariosum sp. nov., holotype, x 1000.
Fig. 4. Phelodinium pachyceras sp. nov., holotype, x 1000.
Fig. 5. Emslandia sp. Middle Headon Beds, sample WC20, showing precingular archaeopyle and cingulum, x 500.
Fig. 6. Phthanoperidinium flebile sp. nov., holotype, x 1000.
Fig. 7. Vectidinium stoveri gen. et sp. nov., holotype, x 1000.
^ V
PLATE 54
liengjarern et al., Eocene/Oligocene dinoflagellates
486
PALAEONTOLOGY, VOLUME 23
Dimensions. Holotype, central body length 50 ^ m , breadth 59 ^m, maximum length of processes 10 ^m.
Range. Central body length 41(47-6)52 ^ m , breadth 48(57-4)64 ^m, processes length (maximum) 6-20 ^m. Specimens measured— 20.
Comparison. In the ragged distal appearance of the ornament, this species resembles Glaphyrocysta divaricata (Williams and Downie 1966), but no process complexes are defined in the latter where the processes are united distally by trabeculae bearing free aculei and/or by perforated membranes in a more complex fashion than in G. paupercula.
G. paupercula also resembles G. intricata (Eaton 1976), G. texta (Bujak 1977), and G. micro- fenestrata (Bujak 1977), where individual process complexes may also be distinguished. However, the distal connections between processes in those species are always more complex than in G. paupercula, while the processes are rarely, if at all, united distally. G. paupercula may be a degenerate offshoot of this lineage.
Genus impletosphaeridium Morgenroth 19666 Type species. Impletosphaeridium transfodum Morgenroth 19666
Impletosphaeridium severinii (Cookson and Cranwell 1967) comb. nov.
1967 Baltisphaeridium severinii Cookson and Cranwell, p. 208, pi. 3, figs. 1, 2.
Comments. This species is transferred to Impletosphaeridium in view of its solid processes. Some specimens appear to show archeopyle sutures; if these eventually prove to be consistent, then I. severinii may have to be transferred once more possibly to Eocladopyxis.
Genus phelodinium Stover and Evitt 1978 Type species. Phelodinium pentagonale (Corradini 1973) Stover and Evitt 1978
Phelodinium pachyceras sp. nov.
Plate 54, fig. 4
Name derivation. Greek, pachys, large, keros, horn.
Diagnosis. Phelodinium characterized by apical and antapical horns, triangular in outline, proximally broad, and distally rounded. Thin-walled cysts moderately compressed dorso-ventrally. Endocyst sub-circular, with low apical and antapical lobes. Apical and antapical pericoels well developed; a narrow ambital pericoel may occur between the horns.
Pericyst ornament atabular of reduced spinules. Pericingulum margins indicated by folds on the periphragm. Perisulcus broad and shallow.
Description. The cyst is thin-walled and usually compressed dorso-ventrally. The ambitus has convex sides and is projected into three prominent horns; these are triangular, with a broad base and a blunt distal ending, and are subequal in size. The epipericyst is more or less conical and somewhat larger than the hypopericyst; the posterior margin of the hypopericyst is straight or slightly concave.
The endocyst is rounded, only weakly bilobed posteriorly; a rounded, low projection into the base of the apical horn may occur. The pericoels are well developed beneath the horns, a narrow pericoel is commonly present between the antapical horns. The ornament is reduced to small spinules or granules, apparently atabular in distribution. Cingulum relatively wide, not indented; its margins are marked by two parallel folds on the periphragm. The sulcus is very broad posteriorly but narrows markedly towards the cingular zone.
The archeopyle is difficult to observe due to the opercula remaining nearly always in place, but the wide posterior archeopyle suture (H4), lying very close to the cingular margin, is evident on most specimens observed.
Holotype. Slide ML 1454, H19/0, sample B6, Upper Hamstead Beds, Lower Oligocene, Bouldnor Cliff, Isle of Wight.
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Dimensions. Holotype, pericyst length 75 /am, breadth 53 /xm, endocyst length 46 ^m, breadth 53 /on, apical horn 12 /un, left antapical horn 15 /xm, right antapical horn 13 /%m.
Range. Pericyst length 57(65)77 /xm, breadth 45(51-6)56 /xin, apical horn 6(9)12 /xm, left antapical horn 9(12)14 /xm, right antapical horn 8(10)13 /xm. Specimens measured— 12.
Distribution. Upper Hamstead Beds (B6, B8), ?Middle Headon Beds WC19.
Comparisons. The prominent broad horns and reduced ornament, as well as a strong dorso-ventral compression, distinguish P. pachyceras from the other species allocated to this genus.
Phelodinium pumilum sp. nov.
Plate 54, fig. 2
Name derivation. Latin, pumilus, dwarf.
Diagnosis. Phelodinium of small size, ambitus bilaterally asymmetrical with reduced antapical horns, right antapical broadly rounded, may be absent. Apical horn small, cylindrical with prominent distal pore. Pericingulum relatively wide, marked by folds. Sulcus distinct.
Description. The ambitus varies from subcircular to distinctly peridinioid: the bilateral asymmetry of the cyst is nearly always evident. The dorso-ventral compression is strong. The pericoels, if observable, are restricted to the cavities beneath the horns. The cylindrical apical horn is distinctive, its truncated distal tip bears a prominent pore bordered by a thickening of the periphragm. The left antapical horn is always developed and is sharply pointed distally. The right antapical horn is often absent but commonly it is represented by a broad lobe.
The periphragm is very thin and transparent and is often folded. The cingulum is only very slightly helicoid, wide in relation to the over-all size of the cyst; anterior and posterior cingular sutures are indicated by low smooth ridges formed by folding of the periphragm. The perisulcus is distinct.
The archeopyle is of a type and shape seen in species of Phelodinium. Peri- and endoperculum are indistin- guishable. The operculum may remain attached along its posterior suture.
Holotype. Slide ML 1450, Q45/4, sample WC 23, Middle Headon Beds, Upper Eocene, Whitecliff Bay, Isle of Wight.
Dimensions. Holotype, pericyst length 64 /xm, breadth 54 /am, apical horn 6 /xm, left antapical horn 5 /xm, right antapical horn 8 /xm.
Range. Pericyst length 50(55)62 fim, breadth 41(46-5)54 /xm, apical horn 3-5(4-5)6-4 (xm, left antapical horn 2-7(4-5)6-5 /xm, right antapical horn 0(1)3 /xm. Specimens measured— 11.
Comparisons. The small size, rounded ambitus, bilateral asymmetry, and distinctive apical horn distinguish this species from all known Phelodinium species. Allocation to Phelodinium is based on the archeopyle shape and relative size, the absence of well-defined pericoels and the very strong dorso-ventral compression.
Distribution. Samples WC18, 20, 21, 23, and 25.
Genus phthanoperidinium Drugg and Loeblich 1967 Type species. Phthanoperidinium amoenum Drugg and Loeblich 1967.
Phthanoperidinium amiculum sp. nov.
Plate 53, fig. 4
Name derivation. Latin, amiculum , cloak.
Diagnosis. Phthanoperidinium with ambitus rounded-pentagonal to suboval. Epicyst with convex sides, terminating in a short apical horn, hypocyst also rounded, produced into one, very occasion- ally two, antapical horns. Peri- and endophragm very closely appressed except beneath the horns.
PALAEONTOLOGY, VOLUME 23
where restricted pericoels develop. Periphragm ornamented with intratabular spinules and peni- tabular to hyaline sutural ridges with smooth to slightly denticulate free edges. Laevigate to striate pandasutural lines may be distinct. Pericingulum and perisulcus laevigate, bordered by membranes.
Description. The pericyst is fusiform in lateral view; the ambitus is rounded-peridinoid to subcircular or sub- oval. The apical horn is short, trangular and distally blunt. The left antapical horn is usually well developed. On some specimens, a right antapical horn, very much reduced, may occur; on most specimens, a projection of the sutural ridges takes the place of the right antapical horn.
The intratabular spines are small and solid, distally short or somewhat capitate; those closer to the paraplate periphery may be arranged in a penitabular ring. The ridges are hyaline and imperforate, their free margins are entire or very slightly serrate to denticulate; the height of the ridges normally does not exceed 3 /j.m, except along the cingular sutures where they may be up to 5 ^m in height. The ridges may be parasutural or peni- tabular in position. Narrow laevigate pandasutural zones are normally observable on parts of the pericyst and, on some specimens, very faint striations, perpendicular to the margin of the paraplate, may be observable.
The paratabulation formula and shape of the paraplates are normal for the genus. The pericingulum is helicoid, its ends being offset about one pericingular width; its surface is laevigate. The perisulcus is relatively narrow, moderately excavated, extending anteriorly to nearly a half of the epicyst height. The archeopyle is formed by the detachment of paraplate 2a, but it is only rarely observable. Occasionally, additional sutures occur along the margins of all three intercalary plates.
Holotype. Slide ML 1451, K23/4, sample WC25, Middle Headon Beds, Upper Eocene, Whiteclilf Bay, Isle of Wight.
Dimensions. Holotype, pericyst length 63 /im, breadth 48 p.m, apical horn 7 /im, left antapical horn 5-5 /un.
Range. Pericyst length 47(55-5)63 ^m, breadth 40(43)48 /urn, apical horn 3(5-5)7 /un, left antapical horn 3(5-5)7 p.m. Specimens measured — 10.
Comparisons. P. eocenicum (Cookson and Eisenack 1965) appears to have sutural ridges and intra- tabular granules, and thus resembles P. amiculum in the style of ornament; but the ambitus in P. eocenicum is fusiform to subpolygonal, less rounded than P. amiculum and the left antapical horn lies closer to the median axis; in addition both intratabular granules and sutural ridges are much more reduced than on the present species.
P. alectrolophum Eaton 1976 resembles P. amiculum in possessing sutural-penitabular ridges, but these bear well-developed spines on their free margins and the intratabular paraplate surfaces are smooth.
Distribution. Only in sample WC25.
Phthanoperidinium flebile sp. nov.
Plate 54, fig. 6
1978 Geiselodinium cf. geiseltalense Krutzsch, Chateauneuf 1978.
Name derivation. Latin, flebilis, pathetic.
Diagnosis. Phthanoperidinium with ?partial (not continuous) endophragm occasionally developed beneath the horns. Ornament intratabular of small echinae or setae, laevigate sutural bands may be observable. Cingulum indicated by a relatively broad equatorial band free of ornament.
Description. The autocyst ambitus is subcircular to oval, but is frequently folded and the ambitus may appear somewhat fusiform; the ambital outline is little affected by the horns. The apical horn is very short, sub- triangular to rectangular in outline; its apical margin may be smooth or may bear a tuft of short spines, to which sometimes the entire horn is reduced. The hypocyst is posteriorly rounded, and may bear a very short, sharp, antapical horn slightly to the left of the median line.
The autophragm is thin and bears a variable number of small setae or echinae, sometimes reduced to granules, atabular to intratabular in distribution; on some specimens the number of spines is reduced, and these may adopt a penitabular arrangement. Sutural bands, when observable, are smooth and of variable width.
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The cingulum, observable on some specimens, appears as a relatively wide band free of ornament; it is not indented. The sulcus has only been seen on one specimen, appearing as a very broad, slightly depressed area with ornament more sparse than on the rest of the ventral autocyst face.
The archeopyle, rarely observable, is intercalary and formed by the loss of paraplate 2a; additional splitting may sometimes develop along the lateral sutures of paraplate 3", but only very rarely, along the sutures of the remaining paraplates in the intercalary series.
Holotype. Slide ML 1453, X27/3, sample H24, Lower Hamstead Beds, Lower Oligocene, Hamstead, Isle of Wight.
Dimensions. Holotype, autocyst length 39 /xm, breadth 28 /xm, apical horn 5 ^m, antapical horn 1 /xm.
Range. Autocyst length 31(35)42 /xm, breadth 22(27)31 /am, apical horn 1(3)5 /xm, antapical horn 0(1)2 /xm. Specimens measured— 20.
Distribution. Sample H24; Lower Hamstead Beds.
Discussion. P. echinatum most closely resembles P. flebile in its ornament of spines, but in P. echinatum these are sutural to penitabular (distribution as a single simulate ring), whereas they are intratabular to atabular in P. flebile.
Occurrence. Sample H24, and at base of Sannoisian in Paris Basin (Argile Verte de Romainville).
Genus thalassiphora Eisenack and Gocht 1960 Type species. Thalassiphora pelagica (Eisenack 1938) Eisenack and Gocht 1960
Thalassiphora fenestrata sp. nov.
Plate 54, fig. 1
Name derivation. Latin, fenestratus, windowed.
Diagnosis. Thalassiphora with partial fenestration of the periphragm. The fenestration is restricted to the lateral and ventral areas of the periphragm. The extent of the fenestrated area is variable, but it never extends over the whole dorsal region. The perforations are large, more or less circular, and may be closely packed forming an irregular reticulum. The ventral flange of the pericyst is narrow and is fenestrated throughout.
Description. This species is similar to T. pelagica in shape and in wall structure but the extension of the periphragm on the ventral side appears to be more reduced than is common in T. pelagica, that is, the ventral lacuna is larger. Perforations develop in the periphragm in ventral and lateral areas and disappear towards the mid-dorsal area. Between these perforations, the fibres are more loosely packed. A large number of smaller perforations occur between the larger fenestrations, the latter are of variable diameter tending to be larger closer to the ambitus. Ventrally, the pericyst occurs as a relatively narrow flange which is strongly fenestrate throughout. The antapical keel may often be reduced or, sometimes, absent.
Holotype. Slide ML 1449 U16/2, sample WC14, Middle Headon Beds, Whitecliff Bay, Isle of Wight. Measurements. Holotype, endocyst 81 x 67 /xm, pericyst diameter 150 /xm.
Range. Endocyst 73(77)89 x 59(67)77 /xm, pericyst diameter 126(154)182 /xm. Specimens measured— 10.
Comments. This species, which is apparently restricted in distribution to the latest Eocene and ?early Oligocene, seems to be an intermediate form between T. reticulata Morgenroth 1966a, which is characteristic of younger Oligocene deposits and whose pericoel is fenestrate virtually all over, and T. pelagica.
Distribution. Samples WC 13-23.
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PALAEONTOLOGY, VOLUME 23
Genus vectidinium gen. nov.
Name derivation. Latin, Vectis, Roman name for the Isle of Wight.
Type species. Vectidinium stoveri sp. nov.
Diagnosis. Single-walled proximate peridinioid cysts, moderately compressed dorso-ventrally, ambitus subpentagonal or subcircular to oval or somewhat fusiform. Epicyst and hypocyst of approximately equal size. Epicyst may or may not extend into a short apical horn; apical pore always present. Hypocyst semicircular or bilobed; left antapical horn present or absent, right antapical horn commonly present.
Autophragm with atabular or intratabular to penitabular ornament of small granules, spinules or baculae, which may be reduced in size and/or number. Narrow laevigate pandasutural zones may be observable. Paratabulation formula, when determinable, 4', 3a, 1", Oc, 5", 2'"', Os. When observable paraplate 1" is rhombic, antero-posteriorly elongate, and relatively large.
Cingulum and sulcus distinct. The cingulum is wide relative to over-all autocyst size, not indented, non- or moderately helicoid. Sulcus shallow and broad on the hypocyst. Archeopyle combination type 31 3P 3"-5", accessory sutures may occur along cingular margin of the remaining precingular paraplates. Opercula free.
Comparisons. Vectidinium differs from Palaeoperidinium Deflandre 1934, and from Saeptodinium Harris 1975, in that the apical paraplate 3' is not included in the archeopyle. From Saeptodinium it also differs in being single walled and usually having intratabular or penitabular ornament. From Palaeoperidinium it differs in the presence of ornament and its much smaller size.
Ginginodinium Cookson and Eisenack 1960, Laciniadinium McIntyre 1975, and Lunatodinium Brideaux and McIntyre 1973, all have a 31 3P 3"-5" archeopyle, and they also resemble Vectidinium in the type of ornament. Ginginodinium is double walled, and in the formation of the archeopyle the three dorsal precingular paraplates (3"-5") always remain attached along their cingular margins (Lentin and Williams 1975, p. 95). Laciniadinium has a single opercular piece 31 3P 3"-5" which always remains attached to the cyst along its posterior margin, like a flap. In Vectidinium whenever the archeopyle is present, the operculum is detached and some doubt remains as to whether this is simple or compound. Lunatodinium (a Lower Cretaceous genus) was described as having an archeo- pyle formed by the loss of the three dorsal precingular paraplates. However, Lentin and Williams (1975, pp. 96 and 116) included this genus in the pericysts, possessing a 31 3P archeopyle. This appears to be so from the original illustration of Lunatodinium (Brideaux and McIntyre 1973, figs. 1-13). The genus is stated to have a circular or subcircular outline.
Cysts of the Recent freshwater dinoflagellate Peridinium resemble Vectidinium in the type and distribution of the ornament, but they are normally cavate and the archeopyle is formed by the detachment of plates along a transapical suture, type A3I3P.
Vectidinium stoveri sp. nov.
Plate 54, fig. 7
Name derivation. This species has been named after Lew Stover.
Diagnosis. As for the genus.
Description. The dorso-ventral compression of these cysts is normally slight, and some specimens may be oriented in apical or antapical view; in lateral view the cysts are somewhat fusiform or oval. The epicyst has strongly convex sides which may merge imperceptibly in a very short, blunt apical horn with a solid tip on which sits a pore; the apical horn may be absent, and the epicyst apex is then invaginate. The hypocyst is com- monly broadly rounded posteriorly, but some specimens may show a weak bilobation on the antapex. The short, eccentrically located left antapical horn may be present or absent.
The ornament varies in density and shape. When the ornament is baculate or of short processes their distal endings are often T-shaped and may be linked to those from near-by processes, giving the appearance of a
LIENGJ ARERN ET AL EOCENE/OLIGOCENE DINOFL AGELLATES
491
tectum supported by columellae in optical section; sometimes the ornament is very reduced in size and mostly consisting of granules. The ornament may be densely or sparsely arranged on the paraplate surface, the most peripheral elements tending to be arranged along simulate rings. Laevigate pandasutural zones, usually narrow, are present but are not always clearly visible.
Cingulum and sulcus are distinct, both being marked by low ridges or folds on the autophragm. The cingulum is relatively wide, slightly helicoid or circular, not indented; intratabular ornament and smooth pandasutural zones may be observable on the cingular surface, but the number of cingular paraplates has not been determined with certainty. The sulcus is also broad and shallow, and extends approximately half-way to the apex. The shape and relative size of individual paraplates are difficult to determine because of very small size and transparent autophragm of these cysts.
When present, the archeopyle is formed by complete detachment of plates la-3a, 3"-5". On some specimens, accessory archeopyle sutures develop along most of the anterior margin of the cingulum, but both portions of the cyst usually remain attached along a narrow band, presumably corresponding to the sulcus. The operculum is always free, but it has not been possible to determine whether this is formed by a single piece or is compound, since isolated opercula have not been observed— a fact suggesting that the operculum may be compound, disintegrating into the very small individual paraplates which would easily be lost in sieving of the organic residue during preparation.
Holotype. Slide ML 1452, U43/3, sample WC34, Upper Headon Beds, Upper Eocene, Whitecliff Bay, Isle of Wight.
Measurements. Holotype, autocyst length 37 ^m, breadth 42 ^m, apical horn 1 /un, left antapical horn 1 ^m, width of cingulum 4 ^m.
Range. Autocyst length 30(35-5)41 ^m, breadth 24-5(31)42 ^m, apical horn 0(2)4-2 /urn, left antapical horn 0(l)4-5 /xm, width of cingulum 2-7(3-6)4 ^m. Specimens measured — 24.
Distribution. The distribution of Vectidinium stoveri in the section studied deserves some special attention since it constitutes monospecific assemblages at some horizons, and has not been found in association with any other dinoflagellate cysts. These horizons yield ostracod assemblages of type III (Keen 1972, 1977); these have been stated by Keen to indicate brackish-water conditions (salinity 3-9%). V. stoveri is thought to be a non-marine dinoflagellate cyst, and possibly a good indicator of oligohaline conditions; it is recorded from samples WC34, 35, and HI 9.
PALYNOLOGICAL ASSEMBLAGES AND DEPOSITIONAL ENVIRONMENTS
The Upper Eocene-Lower Oligocene of the Isle of Wight was deposited under widely variable environmental conditions. The area of deposition has been likened to an embayment, limited to the north and south by the Portsdown and the Sandown-Brixton anticlines respectively, and opening towards the sea to the east and south-east. At times this sea penetrated into the basin. At other times an eastward flowing river system occupied the area (Keen 1977). The conditions ranged from shallow, near-shore open sea, to brackish-water lagoons— with or without connection to the sea— to freshwater lacustrine or fluviatile environments. These changes are reflected in the palyno- assemblages, and are especially noticeable in the relative proportions of different classes of palyno- morphs as well as in the composition of the microplankton assemblages where these occur.
Palaeoecological studies of palynomorph assemblages and particularly of dinoflagellate cysts are currently in their preliminary stages, and no work on the palaeoenvironmental interpretation of Tertiary palyno-assemblages from paralic areas has yet been published. However, the assemblages recovered here may be correlated to particular environmental conditions by using, as a control, the existing information on the distribution of dinocysts in Tertiary to Recent sediments, as well as the sedimentological and faunal evidence available from the sections studied. The foraminifera (Murray and Wright 1974), molluscs (Daley 1973), and ostracods (Keen 1972, 1977; Haskins 1969) from the Upper Eocene-Lower Oligocene sections of the Isle of Wight have yielded a considerable volume of data that can be used in assessing the meaning of the palynological assemblages recovered.
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The major components of the palynological assemblages are indicated in Table 2. They clearly fall into two groups, one with marine dinoflagellates present; the other non-marine samples contain only terrigenous freshwater or lagoonal elements.
The non-marine group shows considerable variation, particularly in the proportions of Pediastrum Meyen, which may contribute from 0 to over 90% of the assemblage. In some samples there is also a considerable contribution from non-marine dinoflagellates. These non-marine samples are asso- ciated with various lithologies ranging from limestone through to sands and no particular pattern has so far been determined. It is evident, particularly from the work of Keen, that the salinities vary from fresh to oligohaline water. The environments of deposition include evidently freshwater lacustrine, fluvial, flood-plain, and bay-head situations. The control over the relative abundance of Pediastrum Meyen is not understood. It is notably more common in the Bembridge Marls in the west of the island. In marine sediments it is present only in very small numbers and is probably allochthonous. It is most abundant in situations that could be interpreted as oligohaline water.
table 2. General character of palynological assemblages. P & S— pollen and spores; Ped —Pediastrum spp.; MD- marine dinoflagellates; fd— freshwater dinoflagellates; ‘r’ indicates that dinoflagellates are all reworked
from older strata.
Sample % P & S % Ped % MD % fd Whitecliff Bay
Bembridge Marls
|
WC67 |
99 |
— |
l(r) |
— |
|
WC66 |
99 |
1 |
x (r) |
— |
|
WC65 |
94 |
2 |
4(r) |
— |
|
WC64 |
99 |
1 |
x(r) |
— |
|
WC63 |
91 |
8 |
l(r) |
— |
|
WC62 |
74 |
26 |
— |
— |
|
WC61 |
100 |
— |
— |
— |
|
WC60 |
100 |
— |
— |
|
|
WC59 |
97 |
3 |
— |
— |
|
WC58 |
100 |
_ |
— |
|
|
WC56 |
99 |
1 |
— |
|
|
WC55 |
13 |
80 |
7 |
— |
|
WC55A |
16 |
84 |
X |
— |
|
WC54 |
100 |
— |
— |
— |
|
WC53 |
100 |
— |
— |
— |
|
Bembridge Limestone WC51 100 |
||||
|
WC49 |
100 |
— |
— |
— |
|
Osborne Beds WC47 |
100 |
|||
|
WC46 |
58 |
42 |
— |
— |
|
WC45 |
36 |
64 |
— |
— |
|
WC44 |
100 |
— |
— |
— |
|
WC43 |
100 |
— |
— |
— |
|
WC42 |
10 |
90 |
— |
— |
|
WC41 |
97 |
3 |
— |
— |
|
Upper Headon Beds WC40 22 |
78 |
|||
|
WC39 |
86 |
14 |
— |
|
|
WC38 |
97 |
3 |
— |
|
|
WC37 |
93 |
6 |
— |
1 |
|
Sample |
% P & s |
% Ped |
% MD |
% fd |
|
WC36 |
99 |
1 |
|
x |
|
WC35 |
62 |
1 |
— |
37 |
|
WC34 |
73 |
14 |
— |
13 |
|
WC33 |
94 |
6 |
— |
_ |
|
WC31 |
62 |
38 |
— |
— |
|
WC30 |
100 |
— |
— |
— |
|
WC29 |
61 |
39 |
— |
— |
|
WC28 |
90 |
10 |
— |
— |
|
WC26 100 Middle Headon Beds |
— |
— |
— |
|
|
WC25 |
74 |
— |
26 |
— |
|
WC24 |
84 |
16 |
— |
|
|
WC23 |
54 |
46 |
— |
|
|
WC21 |
58 |
2 |
40 |
— |
|
WC20 |
40 |
— |
60 |
— |
|
WC19 |
31 |
— |
69 |
— |
|
WC18 |
28 |
— |
72 |
— |
|
WC17 |
38 |
— |
62 |
— |
|
WC16 |
29 |
— |
71 |
— |
|
WC15 |
25 |
75 |
— |
|
|
WC14 |
20 |
80 |
— |
|
|
WC13 37 Lower Headon Beds |
X |
37 |
||
|
WC12 |
72 |
28 |
— |
— |
|
WC9 |
80 |
20 |
— |
— |
|
WC8 |
45 |
55 |
— |
— |
|
WC7 |
25 |
75 |
— |
— |
|
WC6 |
100 |
— |
— |
— |
|
WC5 |
7 |
93 |
— |
— |
|
WC4 |
80 |
20 |
— |
— |
|
WC3 |
96 |
4 |
— |
— |
|
WC2 |
100 |
— |
— |
— |
|
WC1 |
98 |
2 |
— |
— |
LIENGJ ARERN ET AL .: EOCENE/OLIGOCENE DINOFL AGELLATES
493
Sample % P & S % Ped % MD % fd
Hamstead Cliff Lower Hamstead Beds
|
H36 |
54 |
46 |
— |
— |
|
H35 |
55 |
45 |
— |
— |
|
H34 |
88 |
12 |
_ |
— |
|
H33 |
82 |
18 |
— |
— |
|
H32 |
75 |
25 |
— |
— |
|
H31 |
63 |
37 |
— |
— |
|
H30 |
81 |
19 |
— |
— |
|
H29 |
41 |
59 |
— |
— |
|
H28 |
64 |
36 |
— |
— |
|
H27 |
97 |
3 |
— |
— |
|
H26 |
96 |
4 |
— |
— |
|
H25 |
96 |
3 |
— |
— |
|
H24 |
94 |
1 |
6 |
— |
|
H23 |
42 |
13 |
45 |
— |
|
H22 |
84 |
16 |
- |
— |
|
H21 |
87 |
13 |
x |
— |
|
H20 |
78 |
22 |
— |
— |
|
H19 |
63 |
29 |
— |
8 |
|
H18 |
76 |
24 |
— |
— |
|
H17 73 Bembridge Marls |
27 |
— |
— |
|
|
H16 |
76 |
24 |
— |
— |
|
H15 |
34 |
66 |
— |
— |
|
H14 |
67 |
33 |
— |
— |
|
H13 |
64 |
36 |
— |
— |
|
H12 |
36 |
64 |
— |
— |
|
H10 |
34 |
66 |
— |
X |
|
Sample |
% P & S |
% Ped |
% md |
% fd |
|
H9 |
57 |
43 |
_ |
x |
|
H8 |
75 |
25 |
_ |
x |
|
H7 |
73 |
27 |
_ |
_ |
|
H6 |
35 |
6 |
59 |
_ |
|
H4 |
49 |
X |
51 |
_ |
|
H3 44 Bembridge Limestone |
56 |
|||
|
H2 |
16 |
84 |
_ |
— |
|
HI 100 Bouldnor Cliff Upper Hamstead Beds |
||||
|
B15 |
92 |
— |
8 |
_ |
|
B14 |
94 |
— |
6 |
_ |
|
B13 |
96 |
4 |
_ |
_ |
|
B12 |
100 |
— |
_ |
_ |
|
B 1 1 |
24 |
2 |
74 |
_ |
|
BIO |
75 |
25 |
— |
_ |
|
B9 |
42 |
58 |
_ |
_ |
|
B8 |
8 |
3 |
89 |
— |
|
B7 |
28 |
2 |
70 |
_ |
|
B6 |
52 |
29 |
19 |
_ |
|
B5 63 Lower Hamstead Beds |
37 |
x |
— |
|
|
B4 |
100 |
_ |
_ |
_ |
|
B3 |
100 |
_ |
_ |
_ |
|
B2 |
100 |
— |
— |
— |
|
B1 |
52 |
48 |
— |
_ |
Non-marine dinoflagellates are represented by a single species, Vectidinium stoveri which is present only in three samples, WC34, 35, and H19. It is associated with ostracod assemblage III of Keen, indicating brackish-water conditions.
Marine samples are characterized by the presence of marine dinoflagellate cysts and acritarchs. They can be classified into a number of types according to their diversity and the dominant species. Since these types occur in stratigraphic order and are associated with a series of marine incursions it is convenient to discuss them in stratigraphic sequence.
The Middle Headon Beds transgression Four assemblage types are present:
Assemblage 1. The Brockenhurst Bed and Psammobia Beds (samples WC13-21) are characterized by assemblages with forty or more species of dinoflagellate cysts dominated by Homotryblium plectilum which makes up 30-70% of the microplankton; other abundant species are Spiniferites ramosus, Adnatosphaeridium reticulense, and Phthanoperidinium cometum. These assemblages are associated with ostracod assemblage type VI and indicate open-sea conditions, the major transgressive episode in the sequence studied.
Assemblages 2-4. The succeeding Venus Bed contains three different assemblage types showing a marked reduction in the number of species present and in their relative abundance.
Type 2, occurring in sample WC23, has less than thirty species and is dominated by H. pallidum and P. cometum, the latter a species evidently tolerant of reduced salinities in estuarine or lagoonal environments.
494
PALAEONTOLOGY, VOLUME 23
Type 3, occurring in sample WC24, has only seventeen species and is dominated by broken species of H. plectilum associated in assemblage 1 with open-sea conditions. Here these are thought to be allochthonous. H. pallidum is the next most common species.
Type 4, occurring in sample WC25, is dominated by Eocladopyxis tessellata and P. cometum.
These three assemblages appear to indicate a period of regression with restriction of marine access to the area. Keen refers the ostracod assemblages in these beds to his type V, indicating salinities in the range of 16-5-33%.
The Lower Bembridge Marl transgression
Assemblage types 5-7 are associated with the Oyster Bed.
In the east, sample WC55 yielded assemblage type 5, where dinoflagellates made up only 7% of the palynomorphs. No clearly dominant species was present, the commonest being Chiropteridium aspinatum, Glaphyrocysta microfenestrata, Homotryblium pallidum, and Paralecaniella indentata.
In the west, assemblage type 6 is monospecific; Phthanoperidinium levimurale makes up 51% of the palynomorphs in sample H4. Assemblage type 7 is also monospecific, G. microfenestrata making up 59% of the palynomorphs in sample H6.
The significance of these three diverse assemblages from the Oyster Bed is made clearer by consideration of the fauna. Molluscs, foraminifera, and ostracods all indicate brackish estuarine conditions. Assemblage type 5 is associated with Keen’s type V indicating near-marine conditions; the assemblages from the west, however, are associated with his type IV, indicating lower salinities (9-16%). This seems to mean that the monospecific assemblages with P. levimurale and G. micro- fenestrata are composed of more or less stenohaline species, since both also occur in open marine conditions. They appear to have flourished in this estuarine situation since they are particularly abundant, more so than any of the species in the east, where the assemblage, although poorer in relative numbers, has a greater variety of marine species and, although still estuarine, appears to have better connection with the open sea.
The Lower Hamstead Bed transgression
Assemblage types 8 and 9 are associated with a marine incursion at the horizon of the Nematura Band.
Assemblage type 8, sample H23, contains only four species and is dominated by Adnatosphaeridium reticulense. Only 13% of the palynomorphs are dinoflagellates. Assemblage type 9, an even poorer assemblage from H24 immediately above, is on the other hand dominated by P. flebile. Ostracods from the Nematura Band show the presence of assemblage type IV characteristic of mesohaline conditions.
The Upper Hamstead Bed transgressions
Six different dinoflagellate assemblages (types 10-15) have been found in the Upper Hamstead Beds and the palynology appears to show the presence of three different invasions of saline water.
The first incursion corresponds to the Cerithium Bed and contains assemblage types 10-12. Assemblage type 10, sample B6, contains 19% dinoflagellates with only a few species represented and is dominated by G. microfenestratum and P. cometum, both of which, although known from other marine sediments, have previously been noted in assemblage types 7 and 4 and 2, with reduced salinities associated with Keen’s types IV and V. Keen (1972) finds that the Cerithium Bed also yields assemblages of types IV and V. Assemblage type 1 1 in sample B7 is also impoverished in species, but is dominated by small acritarchs of the Micrhystridium group, which accounts for about 60% of the palynomorphs. Assemblage type 12, sample B8, is more varied and richer in numbers, but G. pauper- cula accounts for most of these.
Taken together these three samples indicate a marine influence, which, however, did not achieve fully marine conditions in this locality, the area remaining meso- to polyhaline.
The second incursion is represented only by assemblage type 13, sample Bll. That it is a separate episode is indicated by the intervention of samples B9 and 10 which contain only terrigenous
LIENGJARERN ET AL.. EOCENE/OLIGOCENE DINOFL AGELL ATES
495
pollen and spores and the ?freshwater alga Pediastrum. Assemblage type 13 appears to represent more fully marine conditions with many new species appearing. The dominant species is H. pallidum, which also dominates in assemblage type 2 ( Venus Bed) and is abundant in type 5 (Oyster Bed, WhiteclifF Bay). Here it is associated with Gerdiocysta conopeum. The conditions indicated are still not yet fully marine, but must closely approach that condition.
The third incursion is represented by assemblage types 14 (sample B14) and 15 (sample B15). That this is a separate episode is indicated by the intervention of the purely terrigenous palynological assemblages in samples B12 and 13. The second and third incursions together form the Corbula Bed. Assemblage type 14 is a poor monospecific one comprising only Phthanoperidinium cometum. It probably indicates low salinities. Type 15, however, is somewhat richer and is particularly so in the variety and lack of any clearly dominant species. Micrhystridium , Lejeunia tenella, Hystrichokolpoma salacium, and P. amoenum are prominent, the last three being known only from open marine sediments. It is believed that these two samples B14 and B15 represent the beginning of a major transgression, the culmination of which is not represented due to erosion of the succeeding beds.
DINOFLAGELLATE CYST STRATIGRAPHY
The distribution of dinoflagellates is shown in Table 1.
The first dinoflagellate assemblages appear in the Brockenhurst Bed associated with the Middle Headon transgression. Detailed comparison between the dinoflagellate assemblages from the Solent Formation and the marine sediments of the underlying Barton Formation is not possible at present, since little information on the dinoflagellate content of the Barton Beds has so far been published (Bujak 1976). However, from unpublished evidence (Bujak 1973), it appears that, notwithstanding the intervening regression represented by the Becton and Lower Headon Beds, only minor changes take place in the composition of the assemblages between the uppermost marine beds of the Barton Formation and the lower part of the Solent Formation (Middle Headon Beds). The number of species that first appear in the Middle Headon Beds is very small, but they include Rhombodinium perforatum and Thalassiphora fenestrata, and the possibility remains that some of these may also occur in the Barton Beds; the number of apparent extinctions is also limited, and their stratigraphic significance, which may be only local, cannot be assessed at this stage.
As the assemblages become impoverished towards the upper part of the Middle Headon Beds, among the dinoflagellate species disappearing from the assemblages are Areosphaeridium diktyo- plokus, Cordosphaeridium funiculatum, Distatodinium ellipticum, Palaeocystodinium golzowense, R. draco, R. perforatum, and T. velata.
Other taxa, Emslandia sp., Eocladopyxis tessellata, and Phelodinium pumilum, make their first appearance in the section here. These species first appearing within the upper part of the Middle Headon Beds are all new and so their stratigraphic value, if any, cannot be stated.
The Bembridge transgression, represented by the Oyster Bed, yields poorly diversified assem- blages. These, in terms of their species content, show a somewhat closer relationship to the Middle Headon Beds than to the Upper Hamstead Beds. The Bembridge Oyster Bed at Whitecliff Bay registers the last known occurrence in England of Chiropteridium aspinatum, Impletosphaeridium severinii, Homotryblium oceanicum, and Leptodinium incompositum.
The Lower Hamsted Bed transgression, represented by a thin sequence including the Nematura Bed, also provides a poor assemblage consisting mainly of long-ranging species. One species, Phthanoperidinium flebile is, however, apparently confined to this horizon.
A very pronounced break in the dinocyst succession is evident in the final transgressions of the Upper Hamstead Beds. Out of a total of sixty-eight dinoflagellate species recorded, only nineteen are common to the Solent and Hamstead Formations; thirty-four species disappear below the base of the Hamstead Beds, and fifteen species are first recorded within the latter. The marked renewal of the assemblages registered between the two main marine episodes in the sequence is to some extent environmentally controlled, since some of the species missing in the Headon Bed are known to persist elsewhere into the Oligocene, such as C. aspinatum, Cordosphaeridium cantharellum, D. ellipticum.
496
PALAEONTOLOGY, VOLUME 23
Hystrichokolpoma rigaudiae, Kisselovia coleothrypta, R. draco, T. velata, and T. pelagica. Two species, however, which fail to reappear are R. perforatum and A. diktyoplokus, whose absence seems to be stratigraphically important.
A number of species make their first appearance here and some of them are thought to be stratigraphically important. These are Gerdiocysta conopeum, Heteraulacacysta cf. companula, Phthanoperidium amoenum, Wetzeliella gochtii, and W. symmetrica incisa. Other appearances of possible significance are Phelodinium pachyceras and D. scariosum.
CORRELATION WITH OTHER EUROPEAN AREAS
Paris Basin
Curry et al. (1978) correlate the Middle Headon Beds with part of the Marnes a Pholadomya ludensis, i.e. with the deposits of the Ludian transgression of the Paris Basin. Both formations yield rich dinoflagellate assemblages. A description of those from France has been given by Chateauneuf (1978). Most of the species recorded by him are present in the Middle Headon Beds but there is none of sufficiently restricted range to allow confident correlation on the basis of the dinoflagellates, except that R. perforatum (which appears for the first time in the mid-Headon Beds in England) also appears for the first time in small numbers in the top Marinesian and more commonly in the Ludian. R. perforatum, previously mentioned from the Barton Beds (Costa and Downie 1976) is in fact a separate species (Bujak, in press). A marked distinction between the Ludian assemblages and those from the Headon Beds is the remarkable abundance of H. plectilum in the Isle of Wight and its apparent absence from the Ludian.
The impoverished assemblages from the Bembridge Oyster Bed yield little of correlative value, but the abundance of C. aspinatum does correspond with the prominence of this species in assemblages from the Ludian Marnes a Lucines (Chateauneuf 1978).
The equally poor assemblages from the vicinity of the Nematura Band do, however, show some marked similarities to those of the Argile Verte de Romainville at the base of the Stampian. The lower of the English samples (H23) is dominated by Adnatosphaeridium reticulense, which is also a dominant form in the Argile Verte. The upper English sample (H24) is dominated by Phthanoperi- dinium fiebile, which is restricted to this horizon in England and has also been found to be abundant in the Argile Verte by Chateauneuf (1978) and recorded by him under the name of Geiselodinium cf. geiseltalense. This strongly suggests a correlation between the Nematura Band and a horizon within the Argile Verte de Romainville.
The Upper Hamstead Beds can be correlated with the Calcaire de Sannois and the lower part of the Marnes a Huitres. This correlation is supported by the appearance of Gerdiocysta conopeum ( = Cyclonephelium reticulosum Gerlach, Chateauneuf 1978), W. gochtii (Chateauneuf, pers. comm.), P. amoenum, and the increased abundances of W. symmetrica and Pentadinium taenigerum (Chateauneuf 1978) in both areas.
The overlying Sables de Fontainebleau have a rich and varied dinoflagellate assemblage with species such as Chiropteridium lobospinosum and C. partispinatum (Chateauneuf 1978). In England there is no representative of this assemblage, which has marked similarities to those from the Rupelian of Germany (Benedek 1972).
Belgium
Weyns (1970) described two assemblages from the Sables de Grimmertingen (Lower Tongrian). He listed forty-seven forms of dinoflagellate cysts. Of these thirty-six are apparently present in the Middle Headon Beds, and the assemblages have a general similarity, particularly in the prominence of Homotryblium and Spiniferites.
In comparison with the Hamstead Beds assemblages, there are major differences. The many species appearing for the first time in the Hamstead Beds are not listed in Weyns’s assemblages. Only a few of the species listed by Weyns appear to have stratigraphic significance. Glaphyrocysta micro- fenestrata (= C. semicirculatum in Weyns) does not appear until late in the Chama Beds of the
LIENGJARERN ET AL.\ EOCENE/OLIGOCENE DINOFL AGELL ATES
497
Bartonian (Bujak 1976). G. exuberans ellipsoidalis and Areosphaeridium diktyoplokus are absent above the Middle Headon Beds. The correlation that best fits these circumstances is between the Sables de Grimmertingen and the Middle Headon Beds. This is in agreement with recent work on the nanoplankton correlation (Cavelier 1975). A notable difference between the Belgian and English assemblages is the presence of Leptodinium and Nematosphaeropsis in the former. These are forms found to be more prominent in open-sea situations.
Two samples, one from 20 m and the other from 30 m above the base of the Rupel Clay in the type section, yielded rich dinoflagellate assemblages. These showed marked similarities to those from the Upper Hamstead Beds, in particular containing W. gochtii. However, they also contain C. lobo- spinosum, C. partispinatum and other species which are not present in the Isle of Wight, but are characteristic of the Sables de Fontainebleau in the Paris Basin, and the Rupelton in Germany. These samples are clearly younger than any from the Isle of Wight.
THE EOCENE/OLIGOCENE BOUNDARY IN THE ISLE OF WIGHT
Establishment of a standard for this stratigraphic boundary is the subject of continuing debate. In France, it has commonly been placed at the base of the Stampian Stage, i.e. at the base of the Argile Verte de Romainville (Chateauneuf 1978). Accepting this, the correlations between the Isle of Wight succession and the Paris Basin based on dinoflagellates indicate that the boundary lies closely below the Nematura Band. The boundary clearly lies between the Nematura Band and the Middle Headon Beds. The Oyster Bed, although it has a poor assemblage, has greater similarity to the Headon Beds than to the succeeding assemblage.
Therefore, if the French view is accepted the boundary lies between the base of the Nematura Band and the top of the Oyster Bed. Since the Argile Verte de Romainville marks the first important marine incursion after the episode of the Marnes a Lucines it seems very likely that the Nematura Band represents the same transgression. The Bembridge Marls then correlate with the Supra- and Upper Gypsiferous Groups (1st and 2nd mass) and the Osborne Beds with the 3rd mass of gypsum. The base of the Oligocene could conveniently be taken at the base of the Hamstead Beds, some 9 km below the Nematura Band.
An alternative, widely held, view is that the base of the Oligocene originally selected in Germany should be adopted. This is marked by the transgression associated with the Latdorf (Lattorf) Sands (NP21), which correlate readily with the Sables de Grimmertingen in Belgium.
Dinoflagellates have not been described from the Latdorf Sands, but from the Sable de Grimmer- tingen assemblages very like those from the Middle Headon Beds have been described by Weyns (1970). If this correlation is accepted the Middle Headon Beds would be Oligocene. However, the Brockenhurst Bed has given evidence of an NP20 age, which indicates that the base should be higher. There is, however, no apparent break in the Middle Headon Beds sequence, only a progressive increase in terrigenous influence in the Venus Beds (samples WC22-25). No suitable location for a boundary is evident.
The next marine incursion in the Isle of Wight succession, the Bembridge Oyster Bed, did not yield any dinoflagellates of much value in correlation. Those that are present are not inconsistent with a correlation with the Sables de Grimmertingen and consequently with the placing of the base of the Oligocene immediately above the Bembridge Limestone, as is done by Curry et al. (1978).
Acknowledgements. We particularly thank Dr. J. Bujak for information regarding the Barton Beds and for assisting Dr. Liengjarern in the field; Dr. J. J. Chateauneuf for much unpublished data on the Paris Basin; and Professor D. Curry for helpful comments. Dr. Liengjarern acknowledges the support of a Columbo Plan Scholarship enabling her to do this research. The collections are housed in the Department of Geology, University of Sheffield.
PALAEONTOLOGY, VOLUME 23
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weyns, w. 1970. Dinophycees et acritarches des ‘Sables de Grimmertingen’ dans leur localite-type, et les problemes stratigraphiques du Tongrien. Bull. Soc. beige Geol. Paleont. Hydrol. 79, 247-268. williams, G. l., sarjeant, w. a. s. and kidson, e. j. 1973. A glossary of the terminology applied to dino- flagellate amphiesmae and cysts and acritarchs. Am. Assoc. Stratigr. Palynol., Contrib. Ser. 2, 1-222.
M. LIENGJ ARERN L. COSTA C. DOWNIE
Department of Geology
Manuscript received 21 December 1978 University of Sheffield
Revised manuscript received 18 July 1979 Sheffield SI 3JD
DICTYODORA FROM THE SILURIAN OF PEEBLESSHIRE, SCOTLAND
by m. j. benton and n. h. trewin
Abstract. The meandering trace fossil Dictyodora Weiss, 1 884 occurs in deep water greywacke/shale sequences in the Gala Group (lower Silurian) of Thornylee and Grieston Quarries, Galashiels. Two species are recognized; D. scotica (M‘Coy, 1851) and D. tenuis (M‘Coy, 1851); the former is distinguished by a more regular meandering form. These traces were originally named Crossopodia scotica and Myrianites tenuis. It is suggested that C. scotica be rejected as the type species of Crossopodia.
Thornylee Quarry (Grid ref. NT 4200 3635) (formerly spelt Thornyly, Thorney Lee, Thornielee, Thornilee) is situated on the north bank of the River Tweed, 8 km east of Galashiels and 8 km west of Innerleithen. The quarry is located on a steep slope above a layby on the A72 (Peebles-Galashiels) road. Between the quarry and the road is a dismantled railway with cuttings which provide a 300 m long section through Upper Llandovery greywackes and shales (Gala Group of Lapworth 1870). The first geological description of Thornylee was given by Nicol (1850) who noted some graptolites and abundant ‘annelid impressions’.
Grieston Quarry (NT 3130 3618) was also described by Nicol (1850), who noted the abundant graptolite fauna and the trace fossils. More recently the fauna and sediments of this quarry have been described by Toghill and Strachan (1970) and Trewin (1979). The thin greywackes and shales of Grieston also lie within the top of the Gala Group of Lapworth (1870), but are not exactly the same age as those at Thornylee on the basis of the graptolite fauna.
This study stemmed from work on H. A. Nicholson’s trace fossil collection in Aberdeen (Benton and Trewin 1978). The following descriptions are based on large collections made at Thornylee and Grieston in April and June, 1977. Comparisons have been made with the type material of M‘Coy and Nicholson. Repository abbreviations used are: AUGD, Aberdeen University, Department of Geology and Mineralogy Palaeontology Collection; BMNH, British Museum (Natural History); GSM, Geological Survey Museum, I.G.S., London; HM, Hunterian Museum, Glasgow; SM, Sedgwick Museum, Cambridge.
DEPOSITIONAL ENVIRONMENT AND ASSOCIATED FAUNA
At both localities deep water, interbedded greywacke/shale sequences are exposed in which the coarser lithologies are of turbidite origin. The trace fossils at Thornylee are more abundant in the shale-rich parts of the sequence rather than in association with greywacke beds. There seems to be a greater frequency of meandering traces in the purple rather than the green shales. At Grieston the greywackes are fine-grained and contain abundant ripple-lamination, possibly the results of reworking; other beds are characterized by numerous transported graptolites which produced delicate tool marks on bed bases (Trewin 1979). The greywackes at Thornylee are usually medium grained, graded, and sometimes show tool marks and load casts on the sharp bed bases. Internally, Bouma sequences of structures are frequently seen. The general aspect of the lithofacies is of a low- energy turbidite environment with thin greywacke turbidites and abundant shale.
At both localities graptolites are present but they are much more abundant in the finer grained rocks of Grieston Quarry, where the majority have been transported and deposited in thin turbidites.
[Palaeontology, Vol. 23, Part 3, 1980, pp. 501-513.1
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Tail spines of Ceratiocaris occur at Grieston, but no other fauna was noted. The ichnofauna dominated by meandering feeding burrows is typical of deep water muds and belongs to Seilacher’s Nereites facies.
THE ICHNOFAUNA
Introduction. The ichnofauna is dominated by the meandering burrows of two species of Dictyodora, which are described below. The small burrow Caridolites Etheridge, Woodward and Jones, 1890 is common at both localities. Rare examples of Nereites were found at Thornylee and stuffed burrows, cf. Planolites, are also present. The meandering traces are described below with more emphasis placed on Dictyodora scotica in view of its taxonomic importance. A redescription is given of Caridolites and the association with Nereites briefly discussed.
Genus dictyodora Weiss, 1884 Taxonomic discussion of Dictyodora
Geinitz (1867) founded the species Dictyodora liebeanum for a ‘plant’ from the Culm (Lower Carboniferous) of Gera, East Germany, and Weiss (1884a, b) proposed the genus Dictyodora for this species. He was unable to decide if it was of plant or animal origin.
Zimmermann (1889, 1891) discussed the taxonomic problems associated with German Carbon- iferous Dictyodora, noticing that as with the British examples, different horizontal (bedding parallel) sections had been given distinct names at different times. Zimmermann (1892) gave a detailed account of the type species D. liebeana, and considered that the vertical wall contained no infill, but noted longitudinal and oblique streaks. Zimmermann noted that the wall tends to slope inwards towards the top, giving tighter loops than those of the basal burrow, but was puzzled by walls intersecting without disturbance. D. liebeana has vertical walls up to 1 80 mm high and a well-defined over-all cone shape distinguishing it from D. scotica and D. tenuis. Zimmermann (1892) briefly described a species, D. hercynica, which has a looser structure and walls 1 -3 cm high, found in the Upper Devonian of the Harz mountains. It has apparently not been figured.
D. simplex Seilacher, 1955 from the Lower Cambrian of the Salt Range of Pakistan is a simple, loose structure about 6 mm deep. However, this is a structure built from successive sloping layers and Seilacher proposed that the trace was produced by a worm-like animal travelling through the sediment in an oblique position. There is no basal burrow in Seilacher’s reconstruction and the ‘vertical wall’ is of equal width from top to bottom. We consider that these differences are sufficient to exclude D. simplex from the genus Dictyodora. No alternative generic assignment is suggested without examination of the original material.
Seilacher (1967, p. 77) figured a Dictyodora evolutionary sequence from relatively loosely structured forms in the Lower Palaeozoic to tightly spiralling patterns in the Carboniferous. In grade of organization, D. tenuis appears similar to Seilacher’s most primitive type (a) and D. scotica is slightly more advanced.
Pfeiffer (1959) reviewed previous work on D. liebeana and gave good three-dimensional reconstructions of Carboniferous examples. Muller (1962) also described the morphology of German Lower Carboniferous Dictyodora in detail with many figures, and Ruchholz (1967) gave further examples from the Harz mountains. Pfeiffer (1968) gave a synonomy list for D. liebeana (Geinitz, 1867). Muller (1971) discussed the formation of Dictyodora meanders, emphasizing that the trace was a feeding structure formed relatively rapidly, since the basal burrow does not change in diameter in any single specimen and since it maintains a constant depth and does not rise gradually to keep up with sedimentation.
There is thus an extensive, mainly German, literature on Dictyodora which establishes the characteristic features of the genus as the meandering basal burrow and the dorsal striated wall. The species D. scotica, described below, has previously been given the name Myrianites tenuis for sections for the vertical wall and Crossopodia scotica for the basal burrow.
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The genus Myrianites MacLeay, 1839 was established for a meandering track with small leaf-like extensions at the sides. The type species, M. macleayii Murchison, 1839 (type specimen: GSM Geol. Soc. Coll. 6824) appears to be a small Nereites. Species from Spain described by Delgado (1910) as Myrianites are certainly Dictyodora but are not described or figured well enough to establish synonomy with the material described here.
M‘Coy (1851a, b ) founded the species M. tenuis based on specimens of small meandering traces from Grieston Quarry. Nicholson (1978, pp. 42, 43) identified wall sections of D. scotica from Thornylee as M. tenuis, but the specific name tenuis is retained here for M‘Coy’s original material redescribed below as D. tenuis.
M‘Coy (1851a, b) also founded the genus Crossopodia for two Silurian trace fossils. C. lata from Llandeilo, Wales, is a 2 cm wide trail with clear transverse striations and a ‘fringe’ which better resembles the Crossopodia of modern usage. C. scotica, however, is the form redescribed here as D. scotica and M‘Coy’s type (SM A45575a-c) clearly shows the diagnostic features (text-fig. 2). The figure of the type of C. scotica in M‘Coy 18516, pi. ID, fig. 15, appears to be a composite of the three specimens SM A45575a-c. Fortunately all are of the same species and A45575a is more suitable as the lectotype showing well all the major features. M‘Coy’s figure has been reversed in the engraving process. Unfortunately, Hantzschel (1962, p. W189) designated C. scotica as the type species of Crossopodia and repeated this with a mislabelled figure of ‘C. scotia' (sic) in Hantzschel (1975, fig. 34, 2b). This figure is derived from Schimper and Schenk (1879, p. 52, fig. 40) and is clearly not the C. scotica of M‘Coy (1851a, b) and Nicholson (1978).
In order to preserve the normally accepted usages of Crossopodia and Dictyodora we propose that C. scotica be rejected as the type species of Crossopodia. C. lata M‘Coy (1851) (type specimen SM A37733) would then become the type species of Crossopodia. An application to this effect will be made to the I.C.Z.N. or other appropriate body, when agreement has been achieved on the rules of trace fossil nomenclature. Further revision of the genus Crossopodia is required, but is outside the scope of this paper.
Dictyodora scotica (M‘Coy, 1851)
Text-figs. 1, 2, 3
v* 1851a Crossopodia scotica M‘Coy, p. 395.
v* 18516 Crossopodia scotica M‘Coy; M‘Coy, p. 130, pi. ID, fig. 15.
71855 Crossopodia scotica M‘Coy; Harkness, p. 475. non 1879 Crossopodia scotica (M‘Coy); Schimper and Schenk, p. 52, fig. 40. non 1962 Crossopodia scotia (M‘Coy) (sic); Hantzschel, p. W189, fig. 118, 2. non 1975 Crossopodia scotia (M‘Coy) (sic); Hantzschel, p. W54, fig. 34, 2b. vl978 Crossopodia scotica M‘Coy; Nicholson, p. 36, pi. 3, fig. 1, pi. 6.
vl978 Myrianites tenuis M‘Coy; Nicholson, p. 42, text-fig. 7, non pi. 4, fig. 1. [The same specimen as in Benton and Trewin 1978, pi. 2, fig. 2.] vl978 Crossopodia scotica M‘Coy; Benton and Trewin, p. 8, pi. 2, fig. 1.
Lectotype. Here designated, SM A45575a, the original of M‘Coy (18516, pi. ID, fig. 15). Gala Group, Upper Llandovery, lower Silurian, Thornylee Quarry, nr. Innerleithen, Peeblesshire, Scotland. Refigured here, text-fig. 2.
Other material. More than two hundred examples from the type locality, a representative selection of which are catalogued as AUGD 10693 to 10710. Also: AUGD 8819, 8820, 10606, 10723, Mus. Coll. 956, 957; BMNH 39451, 58169 (1, 2); GSM 104247, 104249, 104250, RU 2970; HM X871/1-2, X1003/1-7.
Description. The burrow system illustrated in text-fig. 1 consists of a basal burrow, generally preserved with a lenticular cross section, and having a vertical or inclined longitudinal wall arising from the dorsal mid-line of the basal burrow. The basal burrow varies from 1-5-6 mm wide and up to 3 mm high in slate lithologies, but when developed in fine sand may have a nearly circular cross section due to the small degree of compaction. The wall is up to 13 mm high and tapers upwards from a width of 1 -2 mm at the base. The taper is most rapid in small examples. The typical burrow system (text-fig. 3c, d, e) consists of 5-10 parallel meanders each 10-80 mm long
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text-fig. 1. Scale bars 10 mm at front faces of figures. Arrows indicate direction of travel of Dictyodora organism, a, general morphology of Dictyodora meanders showing basal burrow and wall; wall curves inwards at meander bends. B, section of burrow to show features of burrow and wall fill, horizontal striations and curved vertical/oblique striations of wall surface, c, block diagram illustrating different preservational aspects of the burrow in plan and section; a, narrow sections at top of wall; b, wider sections near base of wall; c, convex top of basal burrow with base of wall fill preserved on top; d, concave impression of underside of burrow with fill removed, a weak median ridge may be present; e, smaller example showing effect of sectioning the inclined wall at meander turn; /, juvenile burrow in section. The style of ripples and fine parallel lamination present is also illustrated on the front face of c.
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(usually 30-50 mm) and internally measured at basal burrow level as 0-20 mm apart (usually 5-15 mm). Where successive meanders touch, a tight turning circle is present at the meander turn. The meanders may also be irregular and broad as in text-fig. 3a, b. The relevant features of the type specimen are illustrated in text-fig. 2.
The burrow shows various preservational aspects (text-fig. lc) dependent on the level at which it is sectioned. Sections of the wall appear as meandering lines up to 2 mm wide, occasional sharp turns are seen in sections close to the top of the wall (text-fig. 3e) but nearer the basal burrow the wall displays smooth curves. The wall has a finite thickness and the burrow may break either side of the wall as shown in text-fig. 3b. Sections at the top of the basal burrow show the entire infill with a median ridge marking the base of the wall (text-fig. lc). Specimens showing the lower surface of the basal burrow display a smooth groove which is sometimes double, with a weak median ridge (text-fig. lc). The burrow may also split within the burrow fill giving very little relief to the preserved trace. Internally, a distinct pattern is frequently seen in polished or etched cross-sections of the burrow fill resulting from reorientation of platey minerals (text-fig. 1b).
text-fig. 2. Sketch of lectotype of Dictyodora scotica, SM A45575a showing the lower surface of the specimen. Trace A shows the typical meander pattern. Most of the specimen displays the lower surface of the burrow but at a the burrow fill is broken out to show a mould of the upper surface of the basal burrow. The wall of A is 5 mm high and is not seen on the top of the slab. Trace B is larger than A and later since it clearly crosses A. At b the transition from basal burrow to wall can be seen. The wall passes through the full 8 mm thickness of the slab and is seen on the top of the specimen (not illustrated).
The burrows are indistinct in places due to the presence of several crossing burrows, and fracture irregularities on the surface of the slab which have been omitted for clarity.
The wall is normally vertical above straight stretches of burrow, but curves inwards at meander bends (text- figs. 1a, c, 3b, e). Fine bedding parallel striations are present on the surface of the wall closely spaced at 4 per mm. A similar bedding parallel banding due to platey mineral orientation occurs within the wall fill, and is not related to sedimentary laminae. Curved vertical/oblique striations are also present on the wall surface normally spaced at 3-5 per mm. Internally the wall may show fine curved structures marked by reoriented platey minerals and resembling backfill within the wall (text-figs. 1 b, 3b). Detailed observation of features is difficult in the wall fill but it is likely that the possible backfill structures seen normal to bedding occur between the bedding parallel bands.
The smallest forms recognized have a basal burrow 1.5 mm wide and a wall only 1 mm high, and a full gradation exists up to the larger forms with a progressive increase in wall height relative to burrow width (text- fig. 4). Detailed measurement of the morphology and meander patterns of over 170 specimens using principal components analyses failed to differentiate any groups with significantly different characters, and we consider that all the meandering burrows of this type are growth stages of a single species.
text-fig. 3. Dictyodora scoticcr, examples of burrow morphology, a, irregular meanders (section of burrow wall) with example of avoidance of previously formed burrow at a, AUGD 10693. b, irregular burrow which crosses previously formed burrow; plan view shows wall above basal burrow to be partly broken away, and inward slope of wall at meander curves; thickness of slab 10 mm; AUGD 10697. c, D, typical regular meander forms, hooked ends to meanders seen in c; both on AUGD 10694. e, plan view of basal burrow (stipple) and position of top of wall (solid line); sharp bends present at top of wall become smooth curves at lower levels close to the basal burrow; AUGD 10698. All examples from Thornylee Quarry.
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Occurrence. Dictyodora scotica is common at Thornylee Quarry and scarce at Grieston Quarry. It is probably common in the Llandovery strata of the Southern Uplands since Peach and Horne ( 1 899) mention ‘ Crossopodia ’ and ‘ Myrianites ’ from at least twenty localities in the Galashiels-Hawick region. It also occurs in the Llandovery of Penwhapple Glen, Girvan (Nicholson and Etheridge 1880, pp. 304-318). P. Doughty (pers. comm.) also records Dictyodora from the Silurian of Co. Down, Northern Ireland.
H 1 1 1 1 r
1 2 3 4 5 6 W mm
text-fig. 4. Dictyodora scotica. Relationship of width of basal burrow W with burrow height H to show range of variation and the relative increase in wall height in the larger examples.
Dictyodora tenuis (M‘Coy, 1851) Text-fig. 5
v* 1851a Myrianites tenuis M‘Coy, p. 394. v*18516 Myrianites tenuis M‘Coy; M‘Coy, p. 130, pi. ID, fig. 13. vl978 Myrianites tenuis M‘Coy; Nicholson, pi. 4, fig. 1, non text-fig. 7. vl978 Myrianites murchisoni Emmons; Nicholson, p. 43, pi. 5, fig. 1 .
Lectotype. Here designated, SM A45579a, the original of M‘Coy (18516, pi. ID, fig. 13). Gala Group, Upper Llandovery, Lower Silurian, Grieston Quarry, nr. Innerleithen, Peeblesshire, Scotland (text-fig. 5a).
Other material. AUGD 9224, 10329, 10607, 10612, and 10711 to 10720 from Grieston Quarry and AUGD 10710 from Thornylee Quarry.
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Description. Dictyodora with broad irregular meanders, as in text-fig. 5, which frequently have a secondary sinuosity with a wavelength of 3-15 mm which may develop into meanders with length roughly equal to breadth in larger examples. The basal burrow is from T5 to 3 mm wide and the wall has not been observed to exceed 10 mm in height. The wall is 0-2-0-7 mm wide and striated in the same manner as in D. scotica. Traces range from tiny ‘scribbles’ (text-fig. 5e) up to large examples as in text-fig. 5b, d.
Trace endings are observed as in text-fig. 5b where lengths of trace as short as 10 mm occur between inclined circular burrows 3 mm in diameter; other traces can be followed for over 200 mm without interruption.
Discussion. The distinction of D. tenuis from D. scotica can be made on maximum size and on the meandering pattern, which is more regular and smooth in D. scotica compared with the irregular meanders with secondary sinuosity displayed by D. tenuis.
In the past specimens displaying sections of the wall have been identified as Myrianites and specimens showing the basal burrow as Crossopodia or Nemertites. The specimens from Grieston called M. murchisoniby Nicholson (1978, p. 43, pi. 15, fig. 1) are not synonymous with the American form described by Emmons (1844) and are ascribed here to D. tenuis.
Occurrence. Common in the Upper Llandovery ( griestonensis Zone) of Grieston Quarry, nr. Innerleithen, Peeblesshire, and also present in association with much commoner D. scotica at Thornylee Quarry. The form illustrated by Raup and Seilacher (1969, fig. la) from the Ordovician of Barrancos, Portugal, appears to be D. tenuis.
THE DICTYODORA ANIMAL AND ITS BEHAVIOUR
The meandering burrow of Dictyodora resembles the meandering burrows and trails produced by worms and molluscs efficiently utilizing an area as a food source. The tightly packed meanders of Dictyodora were probably formed during feeding, and the looser irregular meanders may have been the result of searching for areas rich in food. We assume that the body of the animal occupied the basal burrow, and probably progressed by peristaltic movement. Since individual burrows cannot be traced from small to large size, and considering that the burrows are sometimes seen to end by rising through the sediment it is likely that the animal moved from place to place on or above the sediment surface. Thus the burrows are considered to be produced by short periods of food search and utilization at a constant level within the sediment.
The animal appears to have maintained contact with the surface by means of an organ which was responsible for the production of the striated wall on the dorsal burrow surface; this we term the wall- organ to avoid assumptions implicit in the use of known zoological terms such as ‘siphon’. The curved vertical striations on the wall and the fill of the wall indicate that the wall-organ moved regularly through the sediments, maintaining a constant convex-forward edge and followed the movement of the animal in the burrow; thus wall-organ traces occasionally touch or cross each other while the corresponding burrows do not.
The behaviour of animals that form meandering traces has been discussed by several authors. Seilacher (1967) suggested that the Dictyodora animal measured its meander length by the length of its body. It maintained contact with a previously formed burrow (thigmotaxis) until its body was straight and then the animal was ‘programmed’ to make a sharp U-turn (homostrophy) as its tail straightened, and to follow beside the last-formed portion of the burrow. However, this explanation does not satisfactorily explain individual burrows where meander length varies, or the Carboniferous Dictyodora where the meanders spiral out from a central point, each meander being longer than its predecessor.
Seilacher based his interpretation on the classic work of Richter (1924, 1928), who studied the Cretaceous/Tertiary Helminthoida labyrinthica Heer, 1865 which forms similar meandering feeding traces. Richter’s interpretation differs from Seilacher’s in one important way: he defined the homostrophic turning stimulus as caused by loss of contact with a former trace and not by tail straightening. The animal followed a former trace and could at times curve in front of previous meander ends (e.g. text-fig. 3c) before turning back when it lost contact with disturbed mud. In text- fig. 3 meander length varies from 30 to 80 mm and was clearly not measured by the body length of the
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text-fig. 5. Dictyodora tenuis. Examples of burrow morphology shown by sections of the wall of the burrow.
a, small meandering trace with irregular meanders showing secondary sinuosity; part of lectotype SM 45579a.
b, parts of typical irregular meanders, together with short lengths of burrow terminated by inclined sections of basal burrow; AUGD 10719. c, d, e, irregular meanders of various sizes to show variation in meander
morphology; c, E AUGD 10716; d AUGD 10718. All from Grieston Quarry.
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animal. The reactions of the animal while feeding in meanders as listed by Seilacher (1967) and Raup and Seilacher (1969) may be modified to:
(1) Move horizontally keeping within a single stratum of sediment (? controlled by wall-organ length);
(2) Always keep in touch with previously formed burrow while feeding (thigmotaxis);
(3) Never come closer to a previously formed burrow than a particular distance ‘d’ (phobotaxis);
(4) If contact is lost with a former burrow, make a 180° turn (homostrophy/strophotaxis).
These ‘rules’ appear to apply reasonably well, and obvious cases of burrow avoidance can be found (text-fig. 3a). Traces made by individuals at different levels in the sediment frequently cross each other, but the basal burrows in such cases are normally at different levels. In the Thornylee examples population density was probably low and thus there was no need for attempting to utilize an area more than once.
If the meandering burrows are formed during feeding then the question arises of how feeding was accomplished. The wall-organ could have been a food collector at the surface, with the animal protected in its burrow, or the animal could have fed by sediment ingestion at burrow level leaving the wall-organ to perform a respiratory function. The second of these suggestions seems most favourable since the basal burrow has a definite burrow fill which corresponds to the sediment type at basal burrow rather than surface level. The apparently passive motion of the wall-organ does not accord with a function as a feeding organ, and it is more likely to have had a respiratory function and to have controlled burrow depth.
In laminated sediment the fill of the wall roughly matches the characteristics of the immediately adjacent sediment, with only slight downward movement of sediment during filling occasionally seen in thin section. Thus the wall-organ does not seem to have had a significant sediment transport function. No annulation of the burrow fill is seen and the constant fine spacing of the striations formed by the wall-organ would seem to indicate a slow regular movement through the sediment. The wall-organ may have been ciliated to facilitate its progress through the sediment. The striations and structured fill of the wall indicate that the organ was not merely dragged through the sediment but that the thin wall of sediment was packed in both horizontal and vertical increments by the wall-organ.
The Dictyodora animal was probably a worm or shell-less mollusc which fed by sediment ingestion and maintained contact with the over-lying water by means of the wall-organ which controlled burrow depth and possibly aided respiration.
OTHER TRACES PRESENT Caridolites wilsoni Etheridge, Woodward and Jones, 1890 Text-figs. 6, 7
The name Caridolites wilsoni was first mentioned in Nicholson (1873) and a brief description appeared in Etheridge, Woodward and Jones (1890), which must rank as the type description. Nicholson’s original (1872) manuscript with a description and figure of C. vw/som'has been published recently together with a discussion (Benton and Trewin 1978, p. 10, pi. 3) in which Nicholson’s interpretation that the trace was made by the tail spines of shoals of swimming Ceratiocaris is rejected.
The traces are generally about 1 mm wide and may consist of a slight central ridge bounded by hollows or a single ridge, or the counterpart of either. The traces are generally nearly straight for from 10-50 mm before disappearing or turning fairly sharply on a new course. Typical examples are shown in text-fig. 6 a-j and typical profiles in text-fig. 61. In cross section the traces are seen to be burrows with a vertical depth of up to 5 mm and consist of a basal tunnel with a narrower vertical extension (text-fig. 6k). These traces thus resemble minute Dictyodora without the meanders. Caridolites frequently covers bedding surfaces with a confusion of burrows as in text-fig. 7.
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text-fig. 6. Caridolites wilsoni. a-j, typical burrow traces as seen on bedding surfaces; a-c, AUGD 10675; d-f, AUGD 10748; i, j, AUGD 7055, Grieston Quarry; g, h, AUGD 10723, Thornylee Quarry, k, typical vertical cross sections of burrows. /, profiles of surface expressions of the burrows.
text-fig. 7. Caridolites wilsoni. Bedding surface covered with typical examples, x 1 , AUGD 10674, Grieston Quarry.
Caridolites is abundant at both Grieston and Thornylee and is frequently associated with both D. scotica and D. tenuis. It seems possible that Caridolites represents the activities of juvenile Dictyodora animals which had not developed sufficiently to meander. Certainly the observed size ranges of the traces fit this possibility.
Genus nereites MacLeay, 1839
Nereites is rare in the Thornylee-Grieston assemblage, with only two clear examples of this surface trace seen. Sediment surface texture was probably not suited to preservation of surface trails and most were probably removed by turbidity currents. The slaty muds and silts generally do not split at the top surfaces of beds. The common association of Nereites surface traces in sequences with Dictyodora burrows of similar width raises the speculation that Nereites could be a surface trace of the Dictyodora animal moving from one feeding spot to another.
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CONCLUSIONS
The deep water ichnofauna of the greywacke/shale turbidite facies of the Llandovery in southern Scotland is dominated by two species of Dictyodora. The small burrow Caridolites is probably the juvenile burrow of the ‘ Dictyodora ’ animal. Nereites is also present but rare, probably owing to original sediment texture and preservation.
Crossopodia scotica is shown to be a Dictyodora, and it is suggested that it should be rejected as the type species of Crossopodia, being replaced by C. lata.
Acknowledgements. We thank the following for the loan of specimens and study facilities: Dr. R. B. Rickards, Sedgwick Museum, Cambridge; Dr. A. W. A. Rushton, Geological Survey Museum, I.G.S., London; Dr. W. D. I. Rolfe, Hunterian Museum, Glasgow; Dr. R. Wilson and Mr. P. J. Brand, I.G.S., Edinburgh; and Mr. D. N. Lewis, British Museum (Natural History).
REFERENCES
benton, m. j. and trewin, n. h. 1978. Discussion and comments on Nicholson’s 1872 manuscript ‘Contributions to the study of errant annelides of the older Palaeozoic rocks’. Pubis. Dep. Geol. Miner. Univ. Aberdeen, 1, 1-16.
delgado, j. f. n. 1910. Terrains paleozoiques du Portugal. Etude sur les fossiles de schistes a nereites de San Domingos et des schistes a nereite et a graptolites de Barrancos. Commis. Serv. geol. Portugal, 56, 1 68, pis. 1-51.
emmons, E. 1844. The laconic system. 68 pp., 6 pis., Albany, New York.
Etheridge, R., woodward, H. and jones, T. R. 1890. Seventh report of the committee on the fossil Phyllopoda of the Palaeozoic rocks. Rep. Br. Ass. Advmt. Sci. for 1889, Trans. Sections, 1890, 63-68. geinitz, h. b. 1867. Uber Dictyophytonl Liebeanum Gein. aus dem Culmschiefer vom Heersberge zwischen Gera und Weyda. Neues Jb. Miner. Geol. Palaont. 1867, 286-288. hantzschel, w. 1962. Trace fossils and problematica. Pp. W177-W245. In moore, r. g. (ed.). Treatise on Invertebrate Paleontology, Part W, Miscellanea. Geol. Soc. Am. and Univ. Kansas Press.
— 1975. Trace fossils and problematica. In teichert, c. (ed.). Treatise on Invertebrate Paleontology, Part W, Miscellanea, Supplement 1, W1-W269, Geol. Soc. Am. and Univ. Kansas Press.
harkness, R. 1855. On the anthracitic shales and the fucoidal remains occurring in the Lower Silurian rocks of the south of Scotland. Q. Jl Geol. Soc. Lond. 11, 468-476. lapworth, c. 1870. On the Lower Silurian rocks of Galashiels. Geol. Mag. 7, 204-209, 279-284. m‘coy, f. 1851a. On some new Protozoic Annulata. Ann. Mag. nat. Hist., ser. 2, 7, 394-396.
— 18516. A systematic description of the British Palaeozoic fossils in the Geological Museum of the University of Cambridge. In Sedgwick, a. A synopsis of the classification of the British Palaeozoic rocks. Parker, London [publ. 1851-1855, pp. 1-184 in 1851],
macleay, w. s. 1839. Note on the Annelida. Pp. 699-701. In Murchison, r. i.. The Silurian System, pt. II, Murray, London.
muller, A. H. 1962. Zur Ichnologie, Taxiologie und Okologie fossiler Tiere. Freiberger ForschHft. C. 151, 5-49.
— 1971. fiber Dictyodora liebeana (Ichnia invertebratorum), ein Beitrag zur Taxiologie und Okologie sedimentfressender Endobionten. Deutsch. Akad. Wiss. Berlin, Monatsber. 13, 136-151.
nicholson, H. A. 1873. Contributions to the study of the errant annelides of the older Palaeozoic rocks. Proc. R. Soc. 21, 288-290.
— 1978. Contributions to the study of the errant annelides of the older Palaeozoic rocks. Pubis. Dep. Geol. Miner. Univ. Aberdeen, 1, 17-47.
— and etheridge, r., jun. 1878-1881. A monograph of the Silurian fossils of the Girvan district in Ayrshire. Vol. 1, Blackwood, Edinburgh and London.
nicol, J. 1850. Observations on the Silurian strata of the southeast of Scotland. Q. Jl geol. Soc. Lond. 6, 53-65. peach, B. N. and horne, J. 1899. The Silurian rocks of Britain. 1, Scotland, xviii + 749 pp. Mem. geol. Surv. U.K. Glasgow.
pfeiffer, H. 1959. fiber Dictyodora liebeana (Weiss). Geologie, 8, 425-439.
— 1968. Die Spurenfossilien de Kulms (Dinants) und Devons der Frankenwalder Querzone (Thuringen). Jb. Geol. 2, 651-717.
raup, d. m. and seilacher, A. 1969. Fossil foraging behaviour: computer simulation. Science, N.Y. 166, 994-995.
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513
richter, r. 1924. Flachseebeobachtungen zur Palaontologie und Geologie. IX. Zur Deutung rezenter und fossiler Maander-Figuren. Senckenbergiana, 6, 141-157.
1928. Psychische Reaktionen fossiler Tiere. Palaeobiologica, 1, 225-244.
ruchholz, k. 1967. Zur Ichnologie und Fazies des Devons und Unterkarbons im Harz. Geologie, 16, 503-527. schimper, w. p. and schenk, a. 1879-90. Palaeophytologie. In zittel, k. a. von (ed.). Handbuch der Palaontologie, II, 1-152 (1879).
seilacher, a. 1955. Spuren und Fazies im Unterkambrium. Pp. 86-143. In schindewolf, o. h. and seilacher, a. Beitrage zur Kenntnis des Kambriums in der Salt Range (Pakistan). Akad. fViss. Lit. Mainz, math.-nat. Kl., Abh. 10.
1967. Fossil behaviour. Scien. Am. 217 (2), 72-80.
toghill, p. and strachan, i. 1970. The graptolite fauna of Grieston Quarry, near Innerleithen, Peeblesshire. Palaeontology, 13, 511-521.
trewin, N. H. 1979. Transported graptolites and associated tool marks from Grieston Quarry, Innerleithen, Peeblesshire. Scott. J. Geol. 15, 287-292.
weiss, E. 1884a. Vorlegung des Dictyophytum Liebeanum Gein. aus der Gegend Von Gera. Sitz.-Ber. Gen. naturf. Freunde, Berlin, 1884, 17.
— 18846. Beitrag zur Culm-Flora von Thiiringen. Jb. Preuss. Geol. Landesanst. 1883, 81-100. zimmermann, E. 1889. Uber die Gattung Dictyodora. Z. dt. geol. Ges. 41, 165-167.
1891. Neue Beobachtungen an Dictyodora. Ibid. 43, 551-555.
1892. Dictyodora liebeana (Weiss) und ihre Beziehungen zu Vexillum (Rouault), Palaeochorda marina
(Gein.) und Crossopodia henrici (Gein.), Jb. Ges. Freunde Naturwiss. Gera, 32-35, 28-63.
M. J. BENTON
Department of Geology University of Newcastle Newcastle-upon-Tyne, NE1 7RU
N. H. TREWIN
Department of Geology and Mineralogy Marischal College University of Aberdeen Aberdeen, AB9 IAS
Manuscript received 15 June 1979
Revised manuscript received 3 September 1979
LOWER CRETACEOUS TEREB R ATULI DAE FROM SOUTH-WESTERN MOROCCO AND THEIR BIOGEOGRAPHY
by FRANK A. MIDDLEMISS
Abstract. The terebratulid brachiopods contained in the Gentil and Whitaker Collections from the Lower Cretaceous of south-west Morocco have been revised. Although the majority of the species are confined to south-west Morocco, the affinities of the fauna are with the faunas of the shallow marine regions bordering Tethys, such as the Jura region, eastern Spain, the Crimea, and the northern Caucasus; the Tethyan pygopid brachiopods characteristic of the Rif in northern Morocco are almost absent. The fauna thus constitutes a Jura- type assemblage situated on the southern side of Tethys. In the systematic section a new genus Paraboubeithyris is erected; also seven new species: Loriolithyris melaitensis, L. marocensis, Boubeithyris tibourrensis , B. pleta, Paraboubeithyris plicae, Kutchithyris kennedyi, and Juralina ecruensis. The genera Kutchithyris and Juralina, previously described from the Jurassic, are shown to have survived into the Lower Cretaceous. Terebratula subsella Leymerie is referred to Kutchithyris.
This paper consists mainly of a revision of the terebratulids contained in two important collections, the Gentil Collection in the Collection de Paleontologie of the Universite Pierre et Marie Curie, Paris, and the Whitaker Collection in the British Museum (Natural History), London. All the specimens came from the Lower Cretaceous (Berriasian to Aptian inclusive) of an area at the seaward end of the High Atlas in south-western Morocco, extending some 40 kilometres inland between Agadir in the south, Essaouira (Mogador) in the centre, and Safi in the north.
Louis Gentil, who was born at Algiers in 1868 and died in Paris in 1925, was a pioneer in the study of the geology of Morocco. His first major contribution was the exploration of the Tafna basin. Later he became a member of the Segonzac exploratory mission to the Atlas Mountains and eventually head of the mission. He was the author of numerous publications, particularly on the geology of the Atlas, almost up to the time of his death including, most notably, the first geological map of Morocco, which appeared in 1923. J. J. S. Whitaker was not a geologist but a Christian missionary who worked in Morocco during the early years of this century. His collection was made at one locality only (see p. 519 below) and very probably on one occasion. Figured specimens are in the British Museum (Natural History) (BM) or the Collection de Paleontologie, Universite Pierre et Marie Curie, Paris (Gentil Coll.).
THE LOWER CRETACEOUS OF SOUTH-WESTERN MOROCCO
The Lower Cretaceous geology of the area was described by Roch (1930) and that of the southern part by Ambroggi (1963); Gigout (1951) included the extreme northern part, around Safi, in his survey; Ager (1974) gave a brief summary in English. All agree that south-western Morocco was, in Lower Cretaceous times, a marine depositional basin opening westwards towards the ocean, cut off from the marine deposits of the same age, but quite different lithofacies and fauna, in the Rif arc to the north by the interposition of the positive block of the Moroccan Meseta and from the marine area of the Algerian high plateaux by the emergent central massif of the High Atlas. At each stage of the Lower Cretaceous the most fully marine conditions, presumably indicating the deepest water, are found in the extreme west, around Cap Ghir and northwards to the neighbourhood of Cap Tafelney. Passing north-eastwards, eastwards, and south-eastwards from this region one finds increasingly
(Palaeontology, Vol. 23, Part 3, 1980, pp. 515-556, pis. 55-61.]
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PALAEONTOLOGY, VOLUME 23
shallow-water lithofacies and biofacies and, usually within 40 or 50 kilometres, non-marine deposits.
The deep-water facies around Cap Ghir consists of green marls and marly limestones with ammonites. These pass eastwards into the more sandy and calcareous beds, with brachiopod and mollusc faunas, of what Roch significantly calls a ‘jurassian facies’. These pass eventually into sub- continental red beds. The lithological succession differs markedly from the monotonous lithofacies of the ‘bathyal’ Lower Cretaceous, seen in the Rif and the Betic region, and has a general resemblance to the successions seen in the Pre-Betic zone of Spain, north-east Spain (Sitges), east-central Sardinia, Provence, and Portugal. It exhibits a very striking difference from these, however, in the absence of the massive urgonian limestones, which are characteristically developed in the Barremian and Aptian of those regions, and of the rudists. In these respects, the south-west Moroccan succession is most comparable to the Lower Cretaceous of central Texas and parts of Coahuila (Mexico). The Aptian,
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
517
as in northern Spain and England, is transgressive, the Gargasian overlapping the earlier divisions on to the flanks of the High Atlas. To the south lies the coastal Cretaceous basin of Tarfaya, at first sight similar in situation to the Agadir-Essaouira basin, but here the earlier part of the Cretaceous is non- marine, marine sedimentation starting only with the Apto-Albian (Choubert et al. 1967).
PALAEOBIOGEOGRAPHICAL RELATIONSHIPS OF THE TEREBRATULID FAUNA
Endemicity. The fauna contains a high proportion of endemic species: of the eleven species described eight are new and seven of these are so far known only from south-west Morocco. This is not unusual. The terebratulids tend to produce local, allopatric species. For example, of the sixteen terebratulid species in the English Aptian thirteen are known only in south and south-central England, of which three occur at one locality only (Middlemiss 1959). I have recently (Middlemiss 1979) pointed to the contrast between such local species and widespread species such as (in the Moroccan fauna) Loriolithyris valdensis and suggested that these differences were probably due to differing lengths of the free-swimming larval stage. Evidence for the palaeobiogeographical relationships of the fauna comes mainly from the occurrence elsewhere of the widespread species but also from the taxonomic relationships of the local species.
Loriolithyris. L. valdensis is the most widespread species of this genus, occurring in the Lower Cretaceous of eastern Spain (and the Balearic Islands), Sardinia, southern France, the Jura, south-east Paris Basin, north-east Bulgaria, the Crimea, northern Caucasus, Kopet Daga, and perhaps Algeria. L. russillensis shares the western part of this distribution— eastern Spain, the Balearic Islands, southern France, the Jura, and south-east Paris Basin. L. melaitensis and L. marocensis are local offshoots from the stock, not at present known outside the south-west Moroccan basin.
text-fig. 2. Palaeobiogeographical relationships of the Lower Cretaceous terebratulids of south-west Morocco. Distribution of south-west Moroccan Lower Cretaceous species which occur elsewhere: ■ Loriolithyris russillensis, □ Loriolithyris valdensis, ♦ Cyrtothyris middlemissi, O Kutchithyris kennedyi. Distribution of other Lower Cretaceous species of Cyrtothyris : + . Distribution of Aptian-Cenomanian species of Boubeithyris: ☆ . Generalized occurrence of Kutchithyris subsella in the Upper Jurassic and Lower Cretaceous: * . Generalized occurrence of Jurassic species of Juralina: + . Generalized boundary of the Tethyan pygopid fauna shown by
diagonal shading.
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PALAEONTOLOGY, VOLUME 23
Boubeithyris and Paraboubeithyris. The three species here ascribed to these genera are all local to south-west Morocco but the genus Boubeithyris, of which Paraboubeithyris is perhaps a specialized development, is represented by a species in the Aptian of the Jura, by two species in the Albian of England and by one species in the Cenomanian of Belgium and western France.
Cyrtothyris. C. middlemissi, the south-west Moroccan species, is known also in eastern Spain and southern France. The genus is more widespread, being represented by species in the early Cretaceous of north Germany, north-east England, and east Greenland and the Aptian of the Jura and southern France. Imlay’s species Terebratula sillimani and T. tamaulipana (Imlay 1937), from the Valanginian-Hauterivian of northern Mexico, probably belong to this genus.
Kutchithyris. K. brivesi is a highly distinctive form confined to south-west Morocco but K. kennedyi is known also in the Lower Cretaceous of eastern Spain, the Balearic Islands, and southern France, the southern part of the same distribution area as L. russillensis. Other species of the genus are found in the Middle Jurassic of India and, according to Buckman (1918), Europe. I here refer Terebratula subsella Leymerie to this genus. This species has a widespread occurrence in the Upper Jurassic of Europe and is known (but undescribed) in the Lower Cretaceous of eastern Spain.
Juralina. This genus, as interpreted by recent authors (especially Boullier 1976), occurs in the Upper Jurassic of a wide area of Europe north of the Alps from England to Russia and also of Crete ( J . immanis—see Bonneau, Beauvais, and Middlemiss 1975) and Sicily (Boullier 1976). J. ecruensis is the first species of the genus to be described from the Cretaceous.
Discussion. The Lower Cretaceous terebratulids of Europe can be divided into three geographical faunas: the boreal fauna in the north, the Tethyan fauna with its distinctive Pygopinae, and between them the Jura fauna. The last is so named after the area in which the fauna is richest and best known, but the character of the Jura fauna is essentially that of a neritic assemblage occupying an optimum situation on the border of the deeper-water Tethyan region and extending approximately parallel to the border of Tethys from the Iberian Peninsula eastwards to Turkmenistan. In this sense, the Lower Cretaceous fauna of south-west Morocco falls into place as an extension of the Jura fauna to the south of the Tethyan fauna which is so strongly developed in the Rif.
The affinities of our terebratulids are essentially with the Jura brachiopod fauna. This is generally true of the cephalopods listed and figured by Roch, Ambroggi, and Gigout. Characteristic Tethyan genera such as Lytoceras (Valanginian-Hauterivian), Phylloceras (Hauterivian), Desmoceras (Barremian), Pulchellia (Barremian), Duvalia (Valanginian), Hibolites (Valanginian) occur but are almost confined to the deep-water region of the extreme west. Further east the cephalopods are noted by Roch as being of ‘Jura type’ and include such genera as Acanthodiscus and Leopoldia. There is scarcely a trace in the pre-Aptian Cretaceous of the Tethyan pygopines which characterize the Rif and the Betic region (Geyssant 1966). The ‘jurassian’ affinities of the faunal facies were clearly recognized by Roch and Gignoux (1955). Ager (1974) has recorded the discovery of Nucleata cf. jacobi in the Aptian or Albian near Tamzargout. This seems to be the only recorded occurrence of pygopine brachiopods in the Lower Cretaceous of south-west Morocco— a feeble sign of southward Tethyan spread’ simultaneous with those transgressions which were causing northward movement of southern species into north Spain, England, and north Germany (Middlemiss 1979). The specimen from Safi figured by Gigout (1951, pi. 9, figs. 35-38) as T. euthymi is a terebratellidine related to ‘ Terebratula ’ moreana d’Orbigny.
Kutchithyris, in the Lower Cretaceous, does not occur north of southernmost France and is one of those sub-Tethyan forms (Middlemiss 1979) which are sensitive indicators of the advance and retreat of the Tethyan fauna. K. subsella shows this well. In the Oxfordian, a period of major expansion of the Tethyan fauna (Arkell 1956), it is found throughout a large part of central Europe— England, northern France, northern and south-western Germany, southern Poland, the Russian Platform. By Kimmeridgian times it extended no further north than the Boulonnais. The Volgian saw a further southward retreat to the Pays de Bray, its place in England and the Boulonnais being taken by boreal forms. In the Lower Cretaceous it has so far been found only in the Pre-Betic region of Spain, on the
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margin of Tethys. Juralina may also be a sub-Tethyan genus whose history is possibly similar to that of K. subsella.
Reconstruction of plate positions as they were in Lower Cretaceous times shows the area of the Jura faunas as much more linear than it is now. Provence, eastern Spain, Sardinia, the Balearic Islands, and south-west Morocco form a linear belt which, extended westwards, would include the western Gulf region of the U.S.A. and the northern parts of Mexico. The neritic Lower Cretaceous of these latter regions is in this sense an extension of the area of the Jura fauna. Unfortunately brachiopods are rare but Imlay (1940) remarked of the Neocomian faunal assemblage of northern Mexico that it was remarkably similar to that of France, England, and Switzerland and belonged decidedly to the ‘Mediterranean’ province. His species T. coahuilensis is certainly close to and probably synonymous with Sellithyris carteroniana d’Orbigny, one of the most characteristic Jura species. It seems a reasonable forecast that neritic Lower Cretaceous brachiopod assemblages of ‘Jura fauna’ affinities will some day be found in the south-eastern or Gulf continental shelf deposits of the U.S.A. or the north-western continental shelf deposits of Africa. Unfortunately those of the offshore part of the Tarfaya basin have yielded no brachiopods.
STRATIGRAPHIC AGES OF SPECIMENS IN THE WHITAKER AND GENTIL COLLECTIONS
Whitaker left no record of the age of the strata from which he made his collection and it has not so far proved possible to trace the exact locality. All the specimens were obtained from one locality, recorded as: ‘Ecru, Mogador, Morocco. 500 ft. on plateau edge of 1000 ft. elevation’. The age can only be assessed on the internal evidence of the fauna and appears to be either Hauterivian or Barremian. The species represented all occur elsewhere in south-west Morocco in both the Hauterivian and the Barremian, whereas not all occur in the Yalanginian or Aptian.
Four species are represented in the Whitaker Collection, in the following numbers: Loriolithyris russillensis, 57; L. valdensis, 39; Juralina ecruensis, 46; Kutchithyris kennedyi, 1 . The predominance of L. russillensis would suggest, on analogy with the occurrence of the species in Switzerland and France, a Barremian age. The distribution of these four species in the Gentil Collection is as follows:
|
L. russillensis |
Hauterivian |
7 |
J. ecruensis |
Valanginian |
25 |
|
Barremian |
39 |
Hauterivian |
2 |
||
|
Aptian |
9 |
Barremian |
15 |
||
|
L. valdensis |
Valanginian |
25 |
K. kennedyi |
Hauterivian |
2 |
|
Hauterivian |
63 |
Barremian |
1 |
||
|
Barremian |
104 |
||||
|
Aptian |
16 |
In general these statistics again support a Barremian age for the Whitaker Collection but they may reflect nothing more than the accidents of collection.
I have followed stratigraphic ages given on the labels of the Gentil Collection because it was not possible to check each locality in the field, but there are some arguments supporting the general validity of these labels, even though there must be a number which are wrong. Analysis of all the localities given on the labels shows that all the specimens from any one locality are assigned consistently either to a single stage or to two, or rarely three, adjacent stages. Thus a logical series of localities can be set out, ranging from those credited with yielding only Berriasian and Valanginian fossils to those credited with yielding fossils only of Clansayesian age.
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SYSTEMATIC PALAEONTOLOGY
Order terebratulida Waagen, 1883 Suborder terebratulidina Waagen, 1883 Superfamily terebratulacea Gray, 1 840 Family terebratulidae Gray, 1840 Subfamily sellithyridinae Muir-Wood, 1965
Remarks. Loriolithyris and Boubeithyris are closely related sellithyridine genera. The corniced hinge plates which are the most distinguishing feature of Boubeithyris are essentially the same in detailed structure as the piped hinge plates of Loriolithyris. Both genera essentially have small crural bases (attached to the inner edges of the hinge plates) which become encased in successive layers of secondary skeletal tissue (PI. 60, fig. 2; PI. 61, figs. 2, 3). The function of this is presumably to strengthen the junction of hinge plates and crural bases. These structures are not inner hinge plates, which some authors claim to be present in Terebratula, although Muir-Wood (1965, p. H775) denies their presence in that genus, because they show no sign of having taken part in any way in the attachment of the dorsal pedicle muscles. Boubeithyris and Loriolithyris differ mainly in the shape of the hinge plates— concave and corniced in Boubeithyris , concave to sigmoid and piped in Loriolithyris. Externally Boubeithyris is distinguished especially by the close spacing of the plicae of the anterior commissure. Both differ from Sellithyris in having accessory structures (cornicing or piping) on the hinge plates and in their much less pentagonal external form.
Paraboubeithyris has an internal structure which is closely related to that of Boubeithyris. Externally P. plicae looks different at first sight from Boubeithyris spp. but similarities include the convex cardinal slopes, small size of the median sinus, and the late development of folding. The external differences, however, seem too great to allow the species to be included in Boubeithyris. P. plicae is here regarded as a specialized local offshoot from the Boubeithyris stock.
Genus loriolithyris Middlemiss, 1968 Type species. Terebratula russillensis de Loriol, 1866.
Species included. T. russillensis de Loriol, T. valdensis de Loriol, L. melaitensis nov., L. marocensis nov. Range: Berriasian to Aptian.
explanation of plate 55
Figs. 1-4. Loriolithyris russillensis (de Loriol). Whitaker Coll. \a-d, typical form, plaster cast of specimen sectioned (see text-fig. 5), BM BB 76544. 2 a-c, wide latifrons- like form, plaster cast of specimen sectioned (see text-fig. 7), BM BB 76552. 3 a-d, small sharply folded form, plaster cast of specimen sectioned (see text-fig. 6) BM BB 76543. 4 a-d, thick latifrons- like form, BM B 17293.
Figs. 5-9. Loriolithyris valdensis (de Loriol). 5 a-c, typical form, plaster cast of specimen sectioned (see text- fig. 11), BM BB 76545. Whitaker Coll. 6 a-d, juvenile rectimarginate form, BM BB 76546, Whitaker Coll. la-d , juvenile incipiently biplicate form BM BB 76549, Whitaker Coll. 8 a-d, elongate adult form, BM BB 76554, Whitaker Coll. 9 a-d, wide adult form, S. 546/1/12, Gentil Coll., Upper Hauterivian, loc. unknown.
Fig. 10 a-c. Loriolithyris melaitensis sp. nov. Plaster cast of specimen sectioned (see text-fig. 12), S.556/1, Gentil Coll., Hauterivian, Tizi Ouarioum.
Figs. 11 a-d. Loriolithyris melaitensis sp. nov. Holotype, S. 556/2, Gentil Coll., Barremian, Ait Ben Melait, Ida ou Guelluill.
All natural size.
PLATE 55
middlemiss, Cretaceous Terebratulidae
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PALAEONTOLOGY, VOLUME 23
Loriolithyris russillensis (de Loriol)
Plate 55, figs. 1-4; text-figs. 3-7
* 1866 Terebratula russillensis de Loriol, p. 88, pi. E, figs. 12-15.
1867 Terebratula russillensis de Loriol, p. 393, pi. C, figs. 28-31.
1869 Terebratula russillensis de Loriol, p. 28, pi. 4, fig. 1 . vl872 Terebratula russillensis de Loriol; Pictet, p. 68, pi. 202, figs. 1-8. vl872 Terebratula latifrons Pictet, p. 67, pi. 201, figs. 16-17.
71964 Sellithyris (7)russillensis (de Loriol); Ager, p. 340. non 1966 Sellithyris russillensis (de Loriol); Bogdanova and Lobacheva, p. 53, pi. 5, figs. 5-6. vl968 Loriolithyris russillensis (de Loriol); Middlemiss, p. 176, pi. A, figs. 1-4.
Lectotype. Museum d’Histoire Naturelle, Geneva (Pictet Collection), no. CB 1520. Designated Middlemiss 1968. Fig. Pictet and de Loriol 1872, pi. 202, fig. 4; from the urgonian of La Russille, Yaud, Switzerland.
Material. Fifty-seven specimens from the Whitaker Collection. About fifty-five specimens in the Gentil Collection.
Remarks. Specimens from Morocco tend to be wider and thinner, in relation to length, than the typical members of the species from La Russille and Orgon and many have the characters of the form described by Pictet (1872) as Terebratula latifrons. I have previously (Middlemiss 1968a) believed the latter form to be a variety of Loriolithyris russillensis and experience of the Moroccan fauna has reinforced this belief. Forms from the Jura region which Pictet recognized as T. latifrons (Geneva Museum) are distinct because of their decidedly small umbones and foramina, not because of their wide depressed shape. They usually display well-developed russillensis-like folding of the shell and as regards shape there seems to be a complete gradation between the two species. In both south-west France and south-west Morocco forms apparently referable to L. russillensis show continuous variation, in the same assemblages, into other forms with the same characters except for the proportions of shell shape, which are those of T. latifrons. The forms with decidedly small umbones and foramina do not occur in these regions. The internal skeletal arrangements revealed by serial sectioning are the same in all these forms: the concave piped hinge plates, situated close to the floor of the brachial valve, and the sigmoid passage from inner socket ridge to hinge plate, are unmistakeable. Pictet records his typical T. latifrons forms only from the Upper Valanginian of Villers-le-Lac and Vesency. L. russillensis was apparently a species-group very variable in proportions of length, width, and thickness, some members of which, in part of the Jura region and for a short time in the Upper Valanginian, became locally sufficiently differentiated to deserve recognition as a subspecies Latifrons' .
30
20
text-fig. 3. Scatter diagrams of relationships of width to length and thickness to length in Loriolithyris russillensis from the Whitaker Collection.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
523
n
10
9
u 7 O
ffl 6 c
< 5
4
3
2
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16
Posterior
5
15 20 25 30
Length
text-fig. 4. Scatter diagrams of the posterior/anterior ratio in Loriolithyris russillensis from the Whitaker Coll.
The main differences between this species and L. valdensis are that L. valdensis is longer is relation to both width and thickness and has a higher P/A ratio than L. russillensis. These points are graphically illustrated, as far as the Moroccan specimens are concerned, in text-figs. 3, 4, 8, 9, and 10. Internally, a point of distinction is that in L. russillensis the hinge plates are close to, or even in part in contact with, the floor of the brachial valve, whereas in L. valdensis they are raised clearly above the floor of the valve for their whole width. It can be added that, internally, L. russillensis has a very short loop, little more than 1 mm from the crural processes to the transverse band in adult shells. Unfortunately it is characteristic of species of Loriolithyris that the transverse band is delicate and seldom preserved and I have never yet seen this structure in L. valdensis.
text-fig. 5. Transverse sections through a small, strongly folded specimen of Loriolithyris russillensis. Sections 1.8 and 2.0 are enlarged in order to show the shape of the juvenile hinge plates enclosed within the cardinal process (punctate tissue is stippled in section 1 .8). Section 4.2 is enlarged in order to show the structure of the piped hinge plates. BM BB 76544, Whitaker Coll. A — scale for sections, 1.8, 2.0 and 4.2. B -scale for the
remaining sections.
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PALAEONTOLOGY, VOLUME 23
Distribution. Ager (1964) claims this species in the Berriasian of the southern Jura and Pictet (1872) notes it in the Valanginian of Sainte-Croix (Vaud). It certainly occurs in the Hauterivian of Vaud, Doubs, Haute-Marne, and Yonne and of Les Corbieres (Aude). It is at its most abundant, however, in the Barremian of Vaud, Jura, the south-east Paris Basin, Bouches-du-Rhone, Gard, Aude, eastern Spain, and Ibiza. It occurs very rarely in the Aptian of Aude. In south-west Morocco it ranges from the Hauterivian to Aptian inclusive.
text-fig. 6. Transverse sections through a small, strongly folded specimen of Loriolithyris russillensis to show the short loop. Section 1.8 is enlarged in order to show the shape of the juvenile hinge plates enclosed in the cardinal process. Sections 2.2 and 2.6 are enlarged in order to show the primary hinge plates (stippled). The maximum height of the crural processes is seen in section 3.4. BM BB 76543, Whitaker Coll. A— scale for sections 1.8, 2.2, and 2.6. B— scale for the remaining sections.
Loriolithyris valdensis (de Loriol)
Plate 55, figs. 5-9; text-figs. 8-11
v*1868 vl872 non 1939 1960 pars 1966 vl968 1972 v!975
Terebratula valdensis de Loriol, p. 52, pi. 4, figs. 9-12.
Terebratula valdensis de Loriol; Pictet, p. 66, pi. 201, figs. 11-15.
Terebratula valdensis var. kentugajensis Moisseev, p. 200, pi. 2, fig. 6.
‘ Terebratula ’ valdensis de Loriol; Smirnova, p. 374, pi. 1, fig. 1.
Sellithyris valdensis (de Loriol); Bogdanova and Lobacheva, p. 55, pi. 5, fig. 7 ( non pi. 7, fig. 11). Loriolithyris valdensis (de Loriol); Middlemiss, p. 182, pi. A, fig. 5.
Sellithyris valdensis (de Loriol); Smirnova, p. 81, pi. 7, fig. 5.
Loriolithyris valdensis (de Loriol); Dieni and Middlemiss, p. 182, pi. 36, figs. 9-10.
Lectotype. Museum d’Histoire Naturelle, Geneva (Arzier Collection), no. CB 1505. Designated Middlemiss 1968. Fig. de Loriol 1868, pi. 4, figs. 9 a-d, from Bed B, Valanginian, Arzier Quarry, Vaud, Switzerland.
Material. Thirty-nine specimens in the Whitaker Collection. About 200 specimens in the Gentil Collection. Eight specimens from Barremian or Aptian, Tizi ou Elma, Agadir (D.V. Ager Collection).
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
525
text-fig. 7. Transverse sections through a broad, latifrons- like specimen of Loriolithyris russillensis. Sections 2.8 and 3.2 are enlarged in order to show the shape of the juvenile hinge plates. The structure of the piped inner margin of the hinge plate is enlarged at section 4.6 (see plate 60, fig. 5). The transverse band was not preserved in this specimen. BM BB 76552, Whitaker Coll. A— scale for sections 2.8, 3.2, and 4.6 (inset). B— scale for the
remaining sections.
Description. Text-figs. 8 and 9 compare the thirty-nine specimens in the Whitaker Collection with a collection of 227 specimens made at the type locality of Arzier by Monsieur Roessinger and preserved at the Geneva Natural History Museum. The isometric development of length and width is well shown in text-fig. 9. Thickness in relation to length develops allometrically, although with a very small differential growth ratio (text-fig. 8). Text- fig. 10 shows that the P/A ratio develops allometrically with a very wide range of variation (about double the width of that shown by Sellithyris sella from the Isle of Wight Aptian (Middlemiss 1968ft, fig. 9)). The smallest shells, less than 5 mm in length, are subcircular in ventral profile but posterior length increases allometrically with growth, at the expense of anterior length. There is a marked tendency for Moroccan specimens to have a lower P/A ratio, i.e. to have a relatively greater anterior length than those from the type area; in this respect the lectotype has an anomalous position.
The anterior commissure remains rectimarginate until the shell is about 12 mm in length. It then passes through a well-marked uniplicate stage until the shell reaches a length of about 16 mm, after which plicae and sinuses are rapidly developed, shells from 17 mm upwards being normally sulciplicate. The episulcate stage is occasionally seen at Arzier but is very rare in Morocco.
Remarks. Differences between this species and L. russillensis were discussed above. Roch remarks on the abundance of this species in the Valanginian and Barremian of south-west Morocco, especially in the Barremian of Jebel Graa and Aghbalou.
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PALAEONTOLOGY, VOLUME 23
L.valdensis
Lectotype of L.valdensis K.kennedyi
=i:Sr
. *
\ %.>•
5 10 15 20 25 30
Length
text-fig. 8. Scatter diagrams of the relationship of thickness to length in Loriolithyris valdensis (Arzier and Whitaker Colls.) and Kutchithyris kennedyi (all available specimens).
text-fig. 9. Scatter diagram of the relationship of width to length in Loriolithyris valdensis (Arzier and Whitaker Colls.).
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
527
Posterior Length
text-fig. 10. Scatter diagrams of the posterior/anterior ratio in Loriolithyris valdensis from Arzier.
35
Distribution. Berriasian and Valanginian of Vaud and Haute-Savoie; Valanginian and Hauterivian of the south-east Paris Basin; Valanginian of Georgia and Hauterivian of the northern Caucasus (Smirnova 1972); Neocomian of the Kopet Daga (Bogdanova and Lobacheva 1966); Hauterivian of north-east Bulgaria. Valanginian and Hauterivian of eastern Spain; Barremian of Basses- Alpes and Alpes-Maritimes. Aptian of La Presta (Neuchatel). In south-west Morocco the range is Valanginian to Aptian inclusive.
text-fig. 1 1 . Transverse sections through Loriolithyris valdensis. Sections 2.8-4.4 are enlarged in order to show the shape of the juvenile hinge plates enclosed within the cardinal process and the structure of the crural bases within the piped inner margins of the hinge plates. Maximum development of the crural processes is seen in section 7.2. The transverse band was not preserved in this specimen. BM BB 76545, Whitaker Coll. A— scale for sections 2.8-4.4. B— scale for the remaining sections.
528
PALAEONTOLOGY, VOLUME 23 Loriolithyris melaitensis sp. nov.
Plate 55, figs. 10, 11; text-fig. 12
vl951 Terebratula salevensis de Loriol; Gigout, p. 360, pi. 9, figs. 15-18.
Types. Holotype, Gentil Collection specimen no. S. 556/2, from the Barremian of Ait Ben Melait. Dimensions: L 31, W 28-5, T 18-5. Paratype, Gentil Collection specimen no. S. 556/1 (locality as holotype).
Material. Ten specimens in the Gentil Collection; nine from the Hauterivian of Tizi Ouarioum, one from the Barremian of Ait Ben Melait, Ida ou Guelluill.
Diagnosis. Loriolithyris of elongate oval ventral profile, becoming thick in adult stage (thickness nearly equal to width); P/A ratio slightly more than 1 . Valves equally convex. Umbo suberect. Foramen mesothyrid, attrite, slightly labiate. Beak ridges rounded. Symphytium very short, but visible. Lateral commissure strongly arched; anterior commissure sulciplicate. Shell not folded except at extreme anterior. Small pedicle collar present. Hinge plates concave, piped. Crural bases well developed. Crural processes slightly incurved. Transverse band high- arched, rounded.
Remarks. The thick, well-filled appearance of the shell, the arched lateral commissure, and the relative lack of folding give this species a superficial resemblance to Tropeothyris salevensis (de Loriol) and it is likely that Ambroggi’s (1963) record of T. salevensis in both Lower and Upper Barremian of south-west Morocco refers to this species.
text-fig. 12. Transverse sections through Loriolithyris melaitensis. Section 4.8 is enlarged in order to show the shape of the juvenile hinge plates enclosed within the cardinal process and the boundary between punctate tissue (stippled) and impunctate laminated tissue. Section 5.2 is enlarged in order to show the primary hinge plates (stippled). The crural bases, unusually large for Loriolithyris, are well shown in sections 6.4-7. 6. Section 9.6 shows the maximum development of the crural processes. S.556/1, Gentil Coll., Hauterivian, Tizi Ouarioum.
A— scale for sections 4.8 and 5.2. B— scale for the remaining sections.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
529
It is distinguished from other species of Loriolithyris especially by the unusually large size of the crural bases attached to the inner edges of the hinge plates (text-fig. 12), but also by its external appearance.
Distribution. Hauterivian and Barremian of south-west Morocco.
Loriolithyris marocensis sp. nov.
Plate 56, figs. 1, 2; text-fig. 13
Types. Holotype, Gentil Collection specimen no. S. 547/2; age given as Upper Hauterivian (locality unknown). Dimensions: L 49-75, W 32, T 26-25. Paratype, Gentil Collection specimen no. S. 547/1.
Material. Sixteen specimens in the Gentil Collection: four from the Hauterivian (including Oued Tidzi), two from the Barremian, Chaine d’Azour, ten from the Barremian of Oued Aghbalou.
Diagnosis. Elongate Loriolithyris , attaining large size; P/A ratio slightly more than 1. Valves equally convex. Umbo erect. Foramen mesothyrid, labiate. Beak ridges rounded. Symphytium hidden in adult stage. Lateral commissure very strongly arched. Anterior commissure sulciplicate with shallow median sinus, rarely episulcate. Shell folded only at extreme anterior, marked by strong concentric growth ridges. Small pedicle collar present.
text-fig. 13. Transverse sections through Loriolithyris marocensis. Sections 5.6 and 6.0 are enlarged in order to show the detailed structure of the cardinal process, with juvenile primary hinge plates (fine stipple) surrounded by laminated thickening and the body of the cardinal process infilled with punctate skeletal tissue (coarse stipple). Section 6.4 is enlarged to show the primary hinge plates (stippled). Maximum development of the crural processes is seen in section 1 1.2. Note the height of the transverse band above the floor of the valve in section 14.4. S. 547/1, Gentil Coll., Hauterivian, locality unknown. A— scale for sections 5.6, 6.0, and 6.4. B— scale for
the remaining sections.
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PALAEONTOLOGY, VOLUME 23
Hinge plates initially concave, becoming rounded L-shaped, piped. Cardinal process extends along the hinge plates, leaving small dorsal umbonal cavity. Transverse band high-arched, with somewhat pointed crest, high above floor of valve.
Remarks. As all the specimens available are fully adult or gerontic little can be said about the ontogeny, except that biplication of the anterior commissure and folding of the shell appear to develop very late. L. marocensis differs from most species of the genus in the large size attained when adult and the massive, little-folded form of the shell; in those respects it is nearest to L. melaitensis but differs markedly from that species in its internal structures: L. melaitensis is distinguished by the large size of its crural bases whereas in L. marocensis the crural bases are small and enclosed within the piped edge of the hinge plate as usual in Loriolithyris. L. marocensis is also distinct from other species of the genus in the L-shape developed by the hinge plates as seen in transverse section (text-fig. 13). Another Moroccan Lower Cretaceous species which closely resembles L. marocensis is Cyrtothyris middlemissi ; the latter is broader in relation to length, and has a less erect umbo, and lacks the loriolithyrid boldly arched lateral commissure of L. marocensis, besides the internal differences.
Distribution. Hauterivian and Barremian of south-west Morocco.
Genus boubeithyris Cox and Middlemiss, 1978 Type species. Terebratula boubei d’Archiac, 1847.
Species included. T. boubei d’Arch. Boubeithyris buzzardensis Cox and Middlemiss, B. tibourrensis nov., B. pleta nov. Range: Hauterivian?, Barremian to Cenomanian.
Boubeithyris tibourrensis sp. nov.
Plate 56, figs. 3, 4; text-fig. 14
Types. Holotype, Gentil Collection specimen no. S. 548/2/1, from Butte de Tibourr’m; labelled Aptian (more likely Barremian). Dimensions: L 20-5, W 16-25, T 12-5. Paratype, Gentil Collection specimen no. S. 552/3/1, Barremian, Tibourr’m.
Material. Two specimens in the Gentil Collection from Butte de Tibourr’m, one labelled Aptian, the other Barremian.
Diagnosis. Boubeithyris regularly oval as seen in ventral profile, apart from short straight anterior (between the lateral plicae). Valves equally convex. P/A ratio slightly greater than 1. Umbo suberect; beak ridges moderately well defined. Foramen mesothyrid, marginate, slightly telate. Lateral commissure arched. Anterior commissure sulciplicate; lateral plicae close together; median sinus narrow. Plication reflected by small folds and sulci in extreme anterior part of brachial valve only. Hinge plates thin, concave, piped to strongly corniced. Inner socket
EXPLANATION OF PLATE 56
Figs. 1, 2. Loriolithyris marocensis sp. nov. 1 a-d, holotype, S. 547/2 Gentil Coll., Upper Hauterivian, loc. unknown. 2 a-c, plaster cast of specimen sectioned (see text-fig. 13), S. 547/1, Gentil Coll., Upper Hauterivian, loc. unknown.
Figs. 3, 4. Boubeithyris tibourrensis sp. nov. 3 a-d, holotype, S.548/2/1, Gentil Coll., Barremian or Aptian, Butte de Tibourr’m. 4 a-c, plaster cast of specimen sectioned (see text-fig. 14), S.522/2/1, Gentil Coll., Barremian, Tibourr’m.
Figs. 5, 6. Boubeithyris pleta sp. nov. 5 a-d, holotype, S. 553/3, Gentil Coll., Barremian, Sidi Bou Rjaa. 6 a-c, plaster cast of specimen sectioned (see text-fig. 15), S.553/1, Gentil Coll., Barremian, Sidi Bou Rjaa.
Fig. 7 a-d. Boubeithyris pleta sp. nov. Large typical specimen, S. 557/6, Gentil Coll., Barremian, Igueni Ouram.
Fig. 8. Paraboubeithyris plicae gen. et sp. nov. 8 a-d, holotype, S. 548/1/3, Gentil Coll., Barremian, Vallee Asif Ait Ameur.
All natural size.
PLATE 56
middlemiss, Cretaceous Terebratulidae
532
PALAEONTOLOGY, VOLUME 23
text-fig. 14. Transverse sections through Boubeithyris tibourrensis. Sections 3.0 and 3.3 are enlarged to show the initial shape of the juvenile hinge plates within the cardinal process. Cornicing of the hinge plates is best seen in sections 4.2-5.4. Section 7.8 shows the maximum development of the crural processes. The transverse band was not preserved in this specimen. S.552/2/1, Gentil Coll., Barremian, Tibourr’m. A— scale for sections 3.0 and 3.3 B— scale for the remaining sections.
ridges narrow. Accessory articulation slightly developed. Euseptoidum short, confined to posterior part of hinge plates, flanked by lateral ridges.
Remarks. This species closely resembles the type species in general shape, the close-set lateral plicae being particularly characteristic of both species. B. tibourrensis differs from B. boubei in being more oval, less pentagonal, in ventral profile and somewhat more convex in lateral profile. Like B. boubei, it differs from B. buzzardensis in being narrower and thicker, having a higher P/A ratio and folding almost confined to the brachial valve. Internally the hinge plates are more deeply concave and the cornice-structure better developed than in either B. boubei or B. buzzardensis. A species of Boubeithyris which occurs in the Aptian of the Jura region, so far undescribed, differs from B. tibourrensis in being still more convex and in having a lateral commissure still more strongly arched, lateral plicae even closer together, and a longer symphytium. Although only two specimens are available, this species is important because it extends back to the Barremian the time-range of the typical oval form of Boubeithyris, which can thence be traced through the undescribed Aptian species from the Jura to B. boubei itself in the Albian and Cenomanian.
Distribution. Barremian of south-west Morocco.
Boubeithyris pleta sp. nov.
Plate 56, figs. 5-7; text-fig. 15
Types. Holotype, Gentil Collection specimen no. S.553/3, from the Barremian of Sidi Bou Rjaa, Oued Tidzi. Dimensions: L 25-5, W 23-75, T 15. Paratypes, Gentil Collection specimens S. 553/1 (age and locality as holotype) and S. 557/6, Barremian, Igueni Ouram.
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533
Material. Twenty-one specimens in the Gentil Collection.
Name. Latin pleta, ‘filled’, from the well-filled appearance of the shell.
Diagnosis. Boubeithyris almost as broad as long, with thickness less than two-thirds of width. Subcircular in ventral profile. Valves equally convex. P/A ratio about 1 . Umbo short, suberect. Beak ridges rounded. Foramen mesothyrid, attrite. Lateral commissure arched. Anterior commissure sulciplicate; median sinus low. Shell little folded. Hinge plates concave, piped to strongly corniced. Euseptoidum short and weak. Transverse band moderately high.
Remarks. In external appearance this species could be taken for a sulciplicate species of Sellithyris but the extremely gentle folding imparts to the shell a tumid or ‘well-filled’ appearance which is distinctive; also the ventral profile is less pentagonal than in most species of Sellithyris , even S. deningeri which is a particularly rounded species of that genus. It differs from other species of Boubeithyris mainly in being relatively wide and flat in comparison with its length and in the wider spacing of the plicae of the anterior commissure.
Distribution. Hauterivian(?) and Barremian of south-west Morocco.
text-fig. 15. Transverse sections through Boubeithyris pleta. Sections 2.8-4.8 are enlarged to show details of the structure of the hinge plates and of the cornicing. Maximum height of the crural processes is seen in section 6.4. S.553/1, Gentil Coll., Barremian, Sidi Bou Rjaa. A— scale for sections 2. 8-4.8. B— scale for the remaining
sections.
Genus paraboubeithyris gen. nov.
Type species. Paraboubeithyris plicae sp. nov.
Diagnosis. Ventral profile rounded pentagonal, as wide as, or wider than, long. Depressed. P/A ratio slightly more than 1. Umbo suberect to erect. Beak ridges rounded. Foramen mesothyrid, marginate, becoming labiate. Lateral commissure strongly arched. Anterior commissure deeply uniplicate, or sulciplicate with very small median sinus. Brachial valve has a strong median fold extending from the umbonal region to the anterior; corresponding to a deep, wide sulcus in the anterior half of the pedicle valve. Hinge plates concave, thin, sharply differentiated from the inner socket ridges; piped to strongly corniced. Transverse band high-arched. Euseptoidum weak, flanked by two low lateral ridges.
534
PALAEONTOLOGY, VOLUME 23 Paraboubeithyris plicae sp. nov.
Plate 56, fig. 8; Plate 57, figs. 1-3; text-fig. 16
Types. Holotype, Gentil Collection specimen no. S. 548/1/3, from the Barremian of the Vallee Asif Ait Ameur. Dimensions: L22, W 22-5, T 10. Paratypes, Gentil Collection specimens S.546/1/1, S. 546/1/2, and S.546/1/3; age given as Upper Hauterivian (locality unknown).
Name. Genitive of Latin plica , ‘a fold’.
Material. Thirty-three specimens in the Gentil Collection, of which ten are from the Barremian of Vallee Asif Ait Ameur and twelve from the Barremian of Ida ou Tanan, the remainder being unlocated.
Description. This species has a deep and dramatic uniplication, especially in the more gerontic specimens. Some of the smaller specimens have a very small median sinus, so that the anterior commissure is strictly sulciplicate, but the sinus is always extremely small and usually asymmetrically placed. We lack juvenile representatives of the
text-fig. 1 6. Transverse sections through Paraboubeithyris plicae. Section 1 .2 shows the pedicle collar (stippled). Section 3.2 shows a dorsal umbonal cavity. The corniced hinge plates are well seen in sections 4.8 and 5.2. S.546/1/1, Gentil Coll., Hauterivian, locality unknown.
EXPLANATION OF PLATE 57
Figs. 1-3. Paraboubeithyris plicae gen. et sp. nov. 1 a-c, plaster cast of specimen sectioned (see text-fig. 16), S.546/1/1, Gentil Coll., Upper Hauterivian, loc. unknown. 2 a-d, adult but uniplicate form, S. 546/1/2, Gentil Coll., Upper Hauterivian, loc. unknown. 3 a-d, elongate form showing incipient biplication, S.546/1/3, Gentil Coll., Upper Hauterivian, loc. unknown.
Fig. 4 a-c. Cyrtothyris middlemissi (Calzada), plaster cast of specimen sectioned (see text-fig. 1 8), BM BB 76564, D.V. Ager Coll., Aptian, Ait Abaid, Agadir.
Figs. 5, 6. Cyrtothyris middlemissi (Calzada). 5 a-c, plaster cast of specimen sectioned (see text-fig. 1 7), BM BB 76565, Calzada Coll., Aptian, La Roqueta, Spain. 6 a-c, BM BB 76566, Calzada Coll., Albian, Peracals, Spain.
All natural size.
PLATE 57
middlemiss, Cretaceous Terebratulidae
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PALAEONTOLOGY, VOLUME 23
species but specimens in the Gentil Collection indicate that the sinus appears late, following juvenile rectimarginate and uniplicate stages, when the shell has attained a length of about 15 mm, and is then lost again in the gerontic stage. Some individuals show no sign of biplication, however.
Remarks. This species is almost certainly the form that both Roch and Ambroggi identified as Terebratula collinaria d’Orbigny, which it resembles in general shape. The principal differences between these two species are (a) T. collinaria is always uniplicate, never biplicate; ( b ) the cardinal slopes of T. collinaria tend to be concave in dorsal profile, with a sharply produced umbo, those of P. plicae are convex, with an umbo which does not protrude beyond the curve of the cardinal slopes; (c) T. collinaria has relatively flat hinge plates with no trace of the corniced structure characteristic of Paraboubeithyris.
Distribution. Barremian of south-west Morocco.
Subfamily rectithyridinae Muir-Wood, 1965 Genus cyrtothyris Middlemiss, 1959
Type species. Terebratula depressa var. cyrta Walker, 1868.
Species included. T. depressa var. cyrta Walker, T. depressa var. uniplicata Walker, T. depressa var. cantabridgiensis Walker, T. seeleyi Walker, T. dallasi Walker, Cyrtothyris middlemissi Calzada, C. cyrta arminiae Middlemiss, ‘ Cyrtothyris ’ maynci Owen. Range: Valanginian to Albian.
Cyrtothyris middlemissi Calzada Plate 57, figs. 4-6; text-figs. 17, 18 * 1972 Cyrtothyris middlemissi Calzada, p. 66, fig. 1.
Holotype. Geological Museum of the Seminario de Barcelona, specimen no. 23.346, from the Aptian of La Roqueta, Garraf, Barcelona.
text-fig. 17. Transverse sections through Cyrtothyris middlemissi. Sections 6.0 and 6.4 are enlarged to show the initial horizontal cuneate shape of the hinge plates. BM BB 76565, Coll. S. Calzada, Aptian, La Roqueta, Spain. A— scale for sections 6.0 and 6.4. B— ^ scale for the remaining sections.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
537
text-fig. 18. Transverse sections through Cyrtothyris middlemissi. Maximum height of the crural processes is seen at 16.4. BM BB 76564, Coll. D. V. Ager, Aptian, Ait Abaid, Agadir, Morocco.
Material. Nineteen specimens in the Gentil Collection (seventeen from the Clansayesian of Sidi Bou Rjaa, one from the Clansayesian of Imi ou Tanant, one from the Aptian of Ait Moujjout). Three specimens from probable Aptian, Ait Abaid, north-east of Agadir (Ager Collection). Also nineteen other specimens: three from the Aptian of La Roqueta (Calzada Collection); four from the Upper Aptian, Plan de Coloubret, Taura, Aude (Charriere Collection); six from the Aptian of Combe Longue, Taura, Aude; two from the Albian of Peracals, Lerida, Spain (Calzada Collection); four from the Albian of Pic du Seigneur, Tuchan, Aude (Debuyser Collection).
Original diagnosis (after Calzada 1972). Large forms (maximum L 53, W 36, T 24; L/W ratio 1-1-1 -6; L/T ratio 1-7-21) of subpentagonal to oval ventral profile. Maximum width and thickness in middle of length. Valves convex, pedicle valve much more so than brachial valve. Valves may show folding (but this character is very variable). Lateral commissure inclined ventralwards at about 20° and arched. Anterior commissure uniplicate to slightly sulciplicate. Umbo wide, massive, suberect to erect. Foramen wide, labiate, circular, mesothyrid. Interareas somewhat concave; beak ridges moderately rounded. Deltidial plates small but visible, fused into a symphytium. Growth lines visible. Hinge plates concave, somewhat clubbed, becoming anteriorly persistently virgate or even V-shaped. Angle between the crural bases and the crural rami 70°-100°. Loop strongly recurved in a posterior direction so that no one serial section includes the whole of the arch of the transverse band.
Remarks. Specimens from Morocco and from the Albian of north-east Spain exceed Calzada’s stated maximum width (up to 43 mm); nevertheless all specimens available fall into the range of L/W ratios given in his diagnosis. On the other hand specimens from both areas, and including the type locality, fall outside the range of L/T ratios given (extremes are specimen MDA 2/1 , from Morocco, 1 -57 and CaP2, from the Albian of Peracals, 2-12). Calzada understates the plication of the anterior commissure, which is normally gently sulciplicate in the adult stage. The foramen should be described
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PALAEONTOLOGY, VOLUME 23
as strongly marginate, labiate in the adult stage. The wide triangular shape of the loop and the strong recurvature of the transverse band are generic features in Cyrtothyris (Middlemiss 1976).
Distribution. Aptian of Aude and north-eastern Spain; Aptian (including Clansayesian) of south- western Morocco; Albian of Aude and north-eastern Spain.
Subfamily uncertain Genus kutchithyris Buckman, 1918
Type species. Terebratula acutiplicata Kitchin, 1900.
Original definition (Buckman 1918). ‘Permesothyrid (beak stout, broad, quite short, thickened with callus, obliquely truncate, foramen large, circular, attrite, close to umbo, symphytium very short); morphogeny, biconvex to strongly sulciplicate; muscle-tracks obliterated posteriorly, not reaching far down valves, rather sharply divergent, starting not from the umbo but from about midway of the posterior half of the shell, showing little more than scars; dorsal septum feeble— ovarian areas large, mammillate on cast. The muscle scars posteriorly obliterated and diverging from a point well removed from the umbo, the short beak with little exposure of symphytium: these characters at once distinguish the genus.’
Diagnosis. Umbo suberect to incurved. Foramen mesothyrid to epithyrid; may be slightly labiate. Development of anterior commissure uniplicate to sulciplicate, more rarely to episulcate. Hinge plates wide, concave, flattening anteriorly, very little differentiated from the laterally deflected inner socket ridges. Crural bases low where attached to hinge plates, rapidly elongating anteriorly and passing into high, thin, slightly flanged crural
text-fig. 19. Transverse sections through Kutchithyris acutiplicata (type species of the genus). Sections 4.8-6.0 are enlarged in order to show details of the structure of the cardinal process. The crural bases first appear at 6.0. The transverse band at 13.6 is broken and partially displaced. BM 52420, Putchum Group (Upper Jurassic), Jumara, Kutch, India. A— scale for sections 4.8-6.0. B— scale for the remaining sections.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
539
5 MM
text-fig. 20. Transverse sections through Kutchithyris subsella. Sections 4.7-5.9 are enlarged to show the initial shape of the hinge plates at 4.7 and 5.1, the primary hinge plates (stippled) at 5.5, and the first appearance of the crural bases at 5.9. Maximum height of the crural processes is seen at 7.9. The transverse band was not preserved in this specimen. BM BB 76555, Kimeridgian, Le Havre, France. A — scale for sections 4.7-5.9. B — scale for the remaining sections.
processes. Hinge plates and crural processes usually clubbed. Descending lamellae thin. Transverse band high- arched, ogival. Euseptoidum present but usually weak; may be bounded by two low euseptoidum-like ridges bounding the adductor impressions.
Remarks. The species here ascribed to this genus differ one from another considerably in external proportions, from the highly convex globular form of Kutchithyris brivesi, through the pentagonal ventral profile of K. acutiplicata and K. subsella to the elongate form of K. kennedyi. They are linked, however, by close similarity in the internal characters, especially those of the hinge plates, inner socket ridges, and crural bases. Buckman erected the genus Kutchithyris mainly to accommodate six species from the Bathonian and Callovian of India previously established by Kitchin but he also included two European species of Deslongchamps and two newly established species of his own from the English Great Oolite (Bathonian) of Bradford-on-Avon, K. fulva and K. egregia.
I here refer to Kutchithyris the species T. subsella Leymerie, a familiar Upper Jurassic species in Europe, which has been previously referred to Sellithyris by Barczyk (1969). I exclude it from Sellithyris mainly because of the lack of differentiation between hinge plates and inner socket ridges, the detailed form of the hinge plates (as seen in transverse section they are like hockey sticks), and the form of the crural processes; these are features which it shares with other species of Kutchithyris. K. subsella survived into the Lower Cretaceous and occurs in the Upper Valanginian of La Querola
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PALAEONTOLOGY, VOLUME 23
. 70
text-fig. 21 . Transverse sections through Kutchithyris subsella. Sections 4.2 and 4.6 are enlarged to show detail of the primary hinge plates. The crural bases are first seen at 5.0. The crural processes are at their maximum height at 9.0. The transverse band was not preserved in this specimen. BM BB 76558, Coll. M. Durand Delga, Niveau 14A, Valanginian, La Querola, Spain. A — scale for sections 4.2 and 4.6. B — scale for the remaining
sections.
EXPLANATION OF PLATE 58
Figs. 1 -6. Kutchithyris kennedyi sp. nov. 1 a-d, holotype, BM BB 76556, Y. Champetier Coll., Hauterivian or Barremian, Oliva, Valencia, Spain. 2 a-c, plaster cast of specimen sectioned (see text-fig. 23), BM BB 76557, Y. Champetier Coll., Hauterivian or Barremian, Oliva, Valencia, Spain. 3 a-d, BM BB 76559, Durand Delga Coll., Valanginian, La Querola, Alicante, Spain. 4 a-c, typical specimen, BM BB 76562, W. J. Kennedy Coll., Lower Barremian, Les Moulins, Mont Chauve, Nice, France. 5 a-c, large adult specimen, plaster cast of specimen sectioned (see text-fig. 24), BM BB 76561, Y. Rangheard Coll., ?Hauterivian, Punta Torreta, Ibiza. 6 a-c, plaster cast of specimen sectioned (see text-fig. 22), S. 552/1/1, Gentil Coll., Hauterivian, Ifrech-Oued- Igouzoulen.
Figs. 7-9. Kutchithyris brivesi (Roch). la-c, plaster cast of specimen sectioned (see text-fig. 26), S. 549/2, Gentil Coll., Hauterivian, Ifrech-Oued-Igouzoulen. 8 a-d, uniplicate specimen, S.549/3, Gentil Coll., Hauterivian, Ifrech-Oued-Igouzoulen. 9 a-d, gerontic episulcate specimen, S. 549/4, Gentil Coll., Hauterivian, Ifrech- Oued-Igouzoulen.
All natural size.
PLATE 58
middlemiss, Cretaceous Terebratulidae
542
PALAEONTOLOGY, VOLUME 23
north of Alcoy, Alicante, Spain (Durand Delga Collection). The other Cretaceous species of the genus, which are described here, are new.
Species included. Bathonian: T. hypsogonia Kitchin, T. acutiplicata Kitchin, T. propinqua Kitchin, T. circumdata Deslongchamps, IK. fulva Buckman, IK. egregia Buckman. Callovian: T. aurata Kitchin, T. jooraensis Kitchin, IT. longicarinata Kitchin, T. subcanaliculata Deslongchamps. Oxfordian to Valanginian: T. subsella Leymerie. Valanginian to Barremian: K. kennedyi nov., K. brivesi (Roch).
Range of the genus. Bathonian to Barremian.
Kutchithyris kennedyi sp. nov.
Plate 58, figs. 1-6; text-figs. 22-24
Types. Holotype, BM BB 76556, from Oliva, Valencia, Spain (Champetier Collection). The horizon is dubious but is probably Hauterivian or Barremian. Dimensions: L 30, W 20, T 18-5. Paratypes. BM BB 76557, Oliva, Valencia, Spain; BM BB 76559, Upper Valanginian, La Querola, Alicante, Spain; BM BB 76561, PuntaTorreta, Ibiza; BM BB 76562 and 76563, Lower Barremian, Mont Chauve, Alpes Maritimes, France; Gentil Collection S. 552/1/1, Hauterivian, Ifrech Oued Igouzoulen, Morocco.
Material. Three specimens from Oliva, Valencia, Spain (Champetier Collection, horizon uncertain). Five specimens from niveau 14A at La Querola, north of Alcoy, Alicante, Spain (Busnardo and Durand Delga 1960)
b
text-fig. 22. Transverse sections through Kutchithyris kennedyi. Section 3.6 is enlarged to show the juvenile primary hinge plates within the cardinal process. The crural bases are first seen at 4.4 and maximum development of the crural processes at 7.2. Sections 3. 6-6.0 S.552/1/1; sections 6.8-10.0 S. 552/1/2. Both specimens Gentil Coll., Hauterivian, Ifrech-Oued-Igouzoulen. A— scale for section 3.6. B— scale for the remaining sections.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
543
(Durand Delga Collection, probably Valanginian). Two specimens from the Lower Barremian of a stream section 800 m north of Les Moulins, east of Mont Chauve, north of Nice, Alpes Maritimes (Kennedy Collection). One specimen from Ecru, Morocco (Whitaker Collection). One specimen from Punta Torreta, Ibiza (Rangheard Collection, probably Hauterivian). Four specimens in the Gentil Collection (three from the Hauterivian of Ifrech Oued Igouzoulen, one from the Barremian of Asif Ait Ameur).
Name. Named after Dr. W. J. Kennedy, who supplied some of the specimens.
Diagnosis. Kutchithyris of elongate oval ventral profile (width about 0-7 length); thickness more than half length. P/A ratio 1 -3—1-6. Umbo suberect to erect in adults. Symphytium very short or invisible. Foramen mesothyrid, labiate. Beak ridges rounded. Anterior commissure sulciplicate to episulcate. Folding of the shell, corresponding to the plicae and sinuses of the commissure, weak and confined to the anterior third of the shell except in gerontic stage.
Description. Because of the few specimens available little can be said about the ontogeny of this species except that the width/length ratio appears to be isometric and to remain constant during growth at a little less than 0-7, whereas the thickness/length ratio is allometric.
text-fig. 23. Transverse sections through Kutchithyris kennedyi. Sections 3. 2-4.0 are enlarged in order to show the juvenile hinge plates within the cardinal process (at 3.2) and the crural bases (at 3.6 and 4.0). Maximum height of the crural processes is seen at 8.0. The transverse band was not preserved in this specimen. BM BB 76557, Coll. Y. Champetier, Oliva, Spain. A — scale for sections 3.2-4.0. B— scale for the remaining sections.
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PALAEONTOLOGY, VOLUME 23
Remarks. This species is easily distinguished from other members of Kutchithyris by its elongate form. The species with which it is most likely to be confused is Loriolithyris valdensis. K. kennedyi is thicker in relation to its length than L. valdensis, because the differential growth ratio of this character is slightly bigger, giving the allometric distribution a slightly steeper slope (fig. 8). In addition, the brachial valve of K. kennedyi is slightly concave in anterior third, that of L. valdensis uniformly convex in lateral view. Internally the characters of the hinge plates, inner socket ridges, and crural bases are all quite different in the two species.
Distribution. ?Valanginian of south-east Spain; Hauterivian and Barremian of south-west Morocco; ?Hauterivian of Ibiza; Lower Barremian of south-east France.
text-fig. 24. Transverse sections through a large, adult specimen of Kutchithyris kennedyi. Sections 5.2 and 5.6 are enlarged to show the juvenile hinge plates (at 5.2) and the primary hinge plates (stippled at 5.6). The crural bases are already visible at 5.6. BM BB 76561, Coll. Y. Rangheard, Punta Torreta, Ibiza. A — scale for sections 5.2 and 5.6. B — scale for the remaining sections.
Kutchithyris brivesi (Roch)
Plate 59, figs. 1, 2; text-figs. 25, 26
v* 1930 Terebratula brivesi Roch, p. 259, pi. 22, figs. 12-13. vl951 Terebratula brivesi Roch; Gigout, p. 361, pi. 9, figs. 27-34.
Lectotype. Roch figured two specimens but there is confusion in the numbering of the figures; figs. 12a and 13 b j[
represent one specimen, figs. 1 2b and 1 3 a the other. The specimen represented by figs. 1 2a and 1 3 b is here chosen as lectotype. It is in the collection of the Service de la Carte Geologique du Maroc at Rabat, bearing the number Ci 55, and is from the Valanginian of Zauouia Embarek des Ida ou Troumma. The label describes it as ‘Coll. E. ; Roch’ but Roch in his caption gives it as ‘Brives Coll.’.
Paratypes. The specimen figured by Roch as figs. 12 b and 13a (at Rabat, bearing the same number as the lecto- type and from the same horizon and locality). A specimen in the Roch Collection at Rabat bearing number P 62 and coming from the Berriasian of Dar Caid Tigzirin. Six specimens in the Roch Collection at Rabat bearing the
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
545
number P 50 and coming from the Valanginian of Oued Igoulouzen. The following specimens in the Gentil Col- lection: S. 549/1, S. 549/2, S. 549/3, S. 549/4, S. 549/5, S. 559/1, all labelled Hauterivian, Ifrech-Oued-Igoulouzen. The two specimens figured by Gigout (both numbered 720 in the Gigout Collection, Universite Mohamed V, Rabat).
Material. Nine specimens from the Roch Collection (detailed above). Forty-eight specimens from the Gentil Collection (forty-five labelled Hauterivian of Ifrech-Oued-Igoulouzen; three labelled Barremian, Chaine d’Azour).
Diagnosis. Kutchithyris highly obese in lateral profile, oval in ventral profile. P/A ratio slightly more than 1 . Brachial valve more convex than pedicle valve. Umbo erect to incurved. Symphytium very short to invisible. Foramen mesothyrid, labiate in older individuals. Beak ridges rounded. Lateral commissure arched. Anterior commissure rectimarginate to sulciplicate or episulcate. Shell tumid and little folded, or not folded. Euseptoidum well developed in the region of the hinge plates and flanked by two lateral ridges.
25r
text-fig. 25. Scatter diagrams of the relationships of thickness to length and thickness to width in Kutchithyris
brivesi (Gentil Coll.).
Description. The growth of this species is accompanied by rapid increase in the thickness/length ratio. In the most adult individuals thickness can exceed width. The smallest specimens available (L 1 8-5) are either rectimarginate or gently uniplicate but the later development of the commissure is the most variable character of the species. Some specimens of 29 mm in length are clearly and deeply uniplicate, while other specimens of similar size are sulciplicate or, rarely, episulcate. In other specimens again a clearly episulcate commissure is developed at a shell length of as little as 19-5 mm.
Remarks. This species is distinguishable at once from other species of Kutchithyris and from all the other species considered here by its globular form and the tumid appearance of both valves. Internally it differs from other species of Kutchithyris in having a well-developed, although short, euseptoidum. Both Roch and Gigout underestimate the plication which the anterior commissure may show in this species. Roch states: ‘La commissure frontale est pratiquement droite, sauf deux petits plis a peine marques.’ According to Gigout: ‘Commissure frontale droite ou tres legerement convexe vers la petite valve.’ The larger specimens (L 25-5) in Roch’s own collection, however, are strongly uniplicate. The form of the anterior commissure of the larger specimens in the Gentil Collection is very variable, suggesting that Roch and Gigout may have seen only small, relatively juvenile specimens such as the lectotype. Roch, Gigout, and Ambroggi all give the main occurrence of this species as of Valanginian age, Roch and Ambroggi recording some also from the Berriasian, whereas the great majority of the Gentil Collection specimens are labelled Hauterivian, with a few labelled Barremian. It is possible that strong sulciplication or episulcation was developed in this species only after the Valanginian. The unity of the species is demonstrated by the remaining
PLATE 59
middlemiss, Cretaceous Terebratulidae
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
547
text-fig. 26. Transverse sections through Kutchithyris brivesi. Section 4.4 is enlarged to show detail of the structure of the cardinal process. The crural bases are first seen at 4.8. The crural processes are at their maximum height at 7.2. S.549/2, Gentil Coll., Hauterivian, Ifrech-Oued- Igouzoulen. A— scale for section 4.4. B— scale for the remaining sections.
EXPLANATION OF PLATE 59
Figs. 1, 2. Kutchithyris brivesi (Roch). 1 a-d, juvenile but incipiently biplicate specimen, S. 549/5, Gentil Coll., Hauterivian, Ifrech-Oued-Igouzoulen. 2 a-d, adult but uniplicate specimen, S.559/1, Gentil Coll., Hauterivian, Ifrech-Oued-Igouzoulen.
Figs. 3-7. Juralina ecruensis sp. nov. 3 a-d, holotype, BM BB 76547, Whitaker Coll. 4 a-d, typical uniplicate form, BM BB 76548. 5 a-d, plaster cast of specimen sectioned (see text-fig. 28), BM BB 76550. 6a-d, juvenile specimen, BM BB 76551. la-d, elongate adult form, BM BB 76553.
All natural size.
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PALAEONTOLOGY, VOLUME 23
characters both external and internal. A specimen from Roch’s collection (from the Valanginian of Oued Igouzoulen) was serially sectioned and differed slightly from the Gentil specimen shown in text- fig. 26 in having hinge plates less concave in their earlier stages, a less developed euseptoidum, and in lacking any clubbed thickening of the hinge plates and crural processes. These are signs of immaturity, confirming that the specimens described by Roch were comparatively juvenile.
Distribution. Berriasian to Barremian of south-west Morocco.
Genus juralina Kyansep, 1961 Type species. Juralina procerus Kyansep.
Original diagnosis (from Kyansep 1961). ‘Shell plano-convex to biconvex. Anterior commissure rectimarginate to uniplicate. Umbo massive, straight to erect. Deltidium high. Socket ridges high. Cardinal process well developed and separated from the floor of the dorsal valve. Hinge plates divided, very narrow, in close proximity to the socket ridges. Crural bases given off ventrally from the hinge plates. Crura narrow, with well-developed, sharp-pointed crural processes. Loop about one-third of the length of the dorsal valve, triangular, with arched transverse band. Pedicle collar shaped like a ring valve. Hinge teeth massive, without denticulae. Adductor muscle impressions oval triangular, narrowing to fine lines posteriorly. Euseptoidum small. Shell smooth, punctate.’
Emended diagnosis. Shell plano-convex to biconvex, depressed (thickness/length ratio low), subcircular in ventral profile. Umbo straight to erect. Foramen mesothyrid, slightly labiate. Lateral commissure oblique to arched; anterior commissure rectimarginate to squarely uniplicate or slightly sulciplicate. Cardinal process well developed. Hinge plates rectangularly virgate (that is, L-shaped in cross-section with an inner lamina at right angles to the outer lamina); clubbed. Crural bases given off from the anterior ventral extremities of the hinge plates. Crural processes high, sharp-pointed, incurved at their extremities. Loop broad; transverse band high- arched, arcuate to trapezoidal.
Remarks. Kyansep considered that his new genus strongly resembled Lobothyris Buckman but Juralina differed in having very narrow hinge plates, high socket ridges, and well-developed crural processes, in lacking a septum to its pedicle collar, and in the elliptical shape of its ventral umbonal cavity. Boullier (1976) has, however, pointed out several additional differences. Kyansep also correctly pointed to a marked external resemblance, but equally marked internal differences, between Juralina and Rectithyris Sahni. In addition to his new species, Kyansep included in Juralina several species from the Jurassic of Europe: Terebratula rauraca Rollier, T. repelliniana D’Orbigny, T. censoriensis Rollier, T. bullingdonensis Rollier, T. cotteaui Douville, and T. moravica Glocker. Of these, T. moravica was referred to a new genus Weberithyris by Smirnova (1969). In her discussion of the genus Boullier (1976) rejects affinities with Lobothyris , Weberithyris , Tropeothyris Smirnova, and Postepithyris Makridin but finds considerable resemblance to Cyrtothyris Middlemiss. Boullier added three more previously established species — T. bauhini, T. valfinensis, and T. subformosa.
Barczyk (1969) added the following species from Upper Jurassic rocks of the Holy Cross Mountains of Poland to Juralina: T. insignis insignis Schiibler, 1 830, T. insignis maltonensis Oppel, 1858, T. immanis immanis Zejszner, 1856, T. immanis speciosa Schlosser, 1882. Of these, Boullier (1976) has since referred T. insignis var. maltonensis Oppel to the genus Galliennithyris as G. maltonensis.
I introduced the terms inner and outer lamina in 1959 and defined them as follows: ‘A virgate hinge plate is divisible into two parts, the outer lamina from the socket ridge to the virgation and the inner lamina on the inner (median) side of the virgation.’ The accompanying figure (Middlemiss 1959, text- fig. 1 j), however, showed cuneate hinge plates with large crural bases. Because of this confusion I later withdrew the terms inner lamina and outer lamina (Dieni et al. 1975; Middlemiss 1976). Now that more is known about the detailed structure of terebratulid hinge plates (Cox and Middlemiss 1978) the terms are seen to be useful in their original sense and I use them here.
Species included. J. procerus Kyansep, ITerebratula rauraca Rollier, IT. repelliniana d’Orbigny, J. graciosa Kyansep, IT. censoriensis Rollier, T. bullingdonensis Rollier, J. naklivkini Kyansep,
MIDDLEMISS: CRETACEOUS TEREBR ATULIDAE
549
T. cotteaui Douville, J. babugani Kyansep, J. earns Kyansep, T. bauhini Etallon, T. valfinensis de Loriol, T. subformosa Rollier, J. ecruensis nov.
Range of the genus. Middle Oxfordian to Barremian.
Juralina ecruensis sp. nov.
Plate 59, figs. 3-7; text-figs. 27, 28
Types. Holotype, BM BB 76547, Whitaker Collection. Dimensions: L 34-5, W 27, T 18. Paratypes: Whitaker Collection specimens BM B 17273, B 17277, BB 76548, BB 76550, BB 76551, BB 76553.
Material. Forty-six specimens in the Whitaker Collection. Forty-two specimens in the Gentil Collection (twenty- five from the Berriasian or Yalanginian of Tinirt Ait Ameur, two from the Hauterivian of an unnamed locality, three from the Barremian of Igueni Ouram, twelve from the probable Barremian of Oued Aghbalou).
Diagnosis. Juralina of subcircular to oval ventral profile; maximum width about the mid-line; valves equally convex. Umbo erect. Foramen mesothyrid, marginate, becoming labiate. Beak ridges rounded. Symphytium short, hidden in adult stage. Shell smooth, with faint growth lines. Lateral commissure oblique to arched. Anterior commissure rectimarginate to squarely uniplicate or slightly sulciplicate. Euseptoidum absent or negligible. Transverse band high-arched, rounded.
Description. Juvenile specimens resemble the adults except in being rectimarginate. At a length of about 22 mm the characteristic adult uniplicate commissure begins to develop. In adults over about 30 mm in length the
30 - 25
10
“5 10 15 20 25 30 35 40 45
Length
i 10~ 15"
20 25 30
Length
35 40 45
25
20
5 10 15 20 25 30 35
Width
text-fig. 27. Scatter diagrams of the relationships of simple dimensions in Juralina ecruensis (Whitaker Coll.).
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PALAEONTOLOGY, VOLUME 23
text-fig. 28. Transverse sections through Juralina ecruensis. The first two sections (upper left) are enlarged in order to show detail of the structure of the cardinal process. Sections 3. 6-5. 2 are enlarged to show the form of the hinge plates and of the crural bases. Maximum height of the crural processes is seen at 8.0. BM BB 76550 except that 4. Ox is from BM B 1 7273 and 3.2 from BM B 1 7277 as these showed better the details of the cardinal process (Whitaker Coll.). A — scale for sections 3.2 and 4.0x. B — scale for sections 3. 6-5. 2. C — scale for the remaining
sections.
uniplica may be angular, the commissure horizontal in the centre; or it may develop a gentle sinus in the centre, giving a slightly sulciplicate stage. The other main gerontic development is that the foramen becomes labiate in specimens over about 30 mm in length. Text-fig. 27 shows that there are a few long, narrow variants and others that are exceptionally thick.
Remarks. This species is referred to Juralina because of ( a) its external appearance, the distinctive elements of which are the biconvex but moderately depressed form and the erect umbo; ( b ) the internal characters, especially the L-shaped form of the hinge plates in transverse section, with the crural bases developed in the extreme ventral tips of the inner laminae in the anterior parts of the hinge plates only. All these characters appear closely comparable to those described and figured by Kyansep (1961), Barczyk (1969), and Boullier (1976).
Distribution. Valanginian to Barremian of south-west Morocco.
EXPLANATION OF PLATE 60
Fig. 1. Loriolithyris melaitensis sp. nov. Section 4.8 of text-fig. 12 photographed to show the shape of the juvenile hinge plates and the distinction between punctate and inpunctate skeletal tissue within the cardinal process.
Fig. 2. Loriolithyris marocensis sp. nov. Part of section 6.0 of text-fig. 13 photographed to show the primary piped hinge plate with its secondary clubbed thickening and the structure of the cardinal process.
Fig. 3. Boubeithyris pleta sp. nov. Part of section 4.0 of text-fig. 1 5 enlarged to show the detailed structure of the junction between hinge plate and inner socket ridge.
Fig. 4. Kutchithyris acutiplicata (Kitchin). Part of section 6.0 of text-fig. 19 enlarged to show the primary hinge plate with its clubbed thickening and the incipient crural base, all enclosed within the cardinal process.
Linear scale = 2 mm.
PLATE 60
middlemiss, Cretaceous Terebratulidae
552
PALAEONTOLOGY, VOLUME 23
TEREBRATULID SPECIES OF MORE DOUBTFUL OCCURRENCE IN THE LOWER CRETACEOUS OF SOUTH-WEST MOROCCO
Terebratula sueuri Pictet is recorded by Gigout from the Valanginian and Hauterivian at Safi and by both Roch and Ambroggi from the Barremian. T. sueuri is a Jura species which is also found rarely in the Hauterivian of the Lower Saxon Basin. Three specimens in the Gentil Collection, S. 544/1 (from Safi), S. 547/2/1, and S. 547/2/2 (both from the Barremian of Ait el Faci) have a close external resemblance to this species and probably represent the form to which the name was applied by previous authors. Serial sectioning proved these to be an undescribed species of terebratellidine, which also occurs in the Jura region (Collections of the Institut de Geologie, Neuchatel). Gigout’s figured specimen (Gigout 1951, pi. 9, figs. 19-22) has a well-developed dorsal median septum and is almost certainly the same terebratellidine species. The occurrence of these two externally similar but quite unrelated species together in the Jura region is a good example of homochronous homoeomorphy.
Terebratula collinaria d’Orbigny is recorded by both Roch and Ambroggi from the Hauterivian and Barremian and by Roch from the Valanginian also. The records probably refer to Para- boubeithyris plicae, although the Gentil Collection contains specimens of this species only from the Barremian.
Tropeothyris salevensis (de Loriol). This is recorded by Gigout from the Valanginian of the environs of Safi and by Ambroggi from the Barremian of his area. On first viewing the collections I referred to T. salevensis the specimens which I have here named Loriolithyris melaitensis; Gigout’s figured specimen (Gigout 1951, pi. 9, figs. 15-18) is apparently similar to these externally except that it is a gerontic specimen. The records probably refer to L. melaitensis.
Moutonithyris moutoniana (d’Orbigny) is recorded by Roch from the Barremian and by Gigout from the ‘Neocomian’ and Aptian of Safi and Sidi Bou Zid. Although Gigout gives in synonymy Pictet’s (1872) figure of the species, not d’Orbigny’s original, his own figured specimen looks reasonably convincing (Gigout 1951, pi. 9, figs. 23-26). In the Gentil Collection are four specimens from the Hauterivian of Oued Tidzi, one from the Hauterivian of Ifrech Oued Igoulouzen, four from the Barremian of Ait el Faci, and seven from the Barremian of Asif Ait Ameur which are probably this species. M. moutoniana is a sub-Tethyan species of very widespread occurrence throughout the Lower Cretaceous (see Middlemiss 1976, 1979) and it would indeed be surprising if some specimens were not to be found in south-west Morocco.
EXPLANATION OF PLATE 61
Fig. 1 . Loriolithyris melaitensis sp. nov. Section 6.8 of specimen S. 556/1 (not included in text-fig. 12) enlarged to show the development of the crural base with secondary clubbing. The primary hinge plate has a cuneate relationship to the crural base.
Fig. 2. Loriolithyris melaitensis sp. nov. Section 4.8 of text-fig. 1 2 photographed to show the internal structure of the cardinal process, especially the distribution of punctate and impunctate skeletal tissue. The juvenile primary hinge plates have a secondary clubbed thickening which was deposited prior to the incorporation of the hinge plates into the cardinal process.
Fig. 3. Loriolithyris melaitensis sp. nov. Section 5.2 of text-fig. 12 enlarged to show the primary hinge plate surrounded by secondary tissue and the first sign of development of the crural base within the piped inner margin of the hinge plate.
Fig. 4. Loriolithyris russillensis (de Loriol). Section 4.6 of text-fig. 7 enlarged to show the structure of the piped inner margin of the hinge plate.
Fig. 5. Paraboubeithyris plicae gen. et sp. nov. Part of section 4.8 of text-fig. 16 enlarged to show the structure of the corniced inner margin of the hinge plate.
Linear scale = 2 mm.
PLATE 61
middlemiss, Cretaceous Terebratulidae
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PALAEONTOLOGY, VOLUME 23
Sellithyris carteroniana (d’Orbigny) is recorded by Roch from the Berriasian and the Barremian, by Gigout from the Valanginian (of Safi) and by Ambroggi from the Hauterivian. In the Gentil Collection there is one specimen from Tinirt Ait Ameur (probably Hauterivian) which has some resemblance to S. carteroniana in being obese, equidimensional, and strongly episulcate but the resemblance is closer, in fact, to the Algerian variety or subspecies of S. sella (see below). The same can be said of Gigout’s figured specimen (Gigout 1951, pi. 9, figs. 11-14). S. carteroniana is an interesting species from the palaeobiogeographical point of view as (a) it is a characteristic member of the Jura fauna which is also found in north Germany during the time of the Valanginian-Hauterivian transgression (Middlemiss 1976, 1979) and ( b ) Terebratula coahuilensis of the Neocomian of northern Mexico is probably synonymous with it. In view of my thesis of the Jura affinities of the south-west Moroccan fauna the occurrence of this species would be significant. Unfortunately there is no evidence that all the records do not refer to S. sella, although some may refer to Boubeithyris pleta.
Sellithyris sella (J. de C. Sow) is recorded by both Roch and Ambroggi from the Barremian and Gargasian and by Roch from the Bedoulian also. This almost ubiquitous Lower Cretaceous species would be expected to occur in south-west Morocco, especially as an undescribed form of it is certainly known from the Lower Cretaceous of the High Plateaux region of Algeria. In the Gentil Collection are twenty-three specimens from Tinirt Ait Ameur (labelled Berrisian-Valanginian but more likely Hauterivian) which appear to be this obese Algerian variety of the species. There is also one specimen from the Hauterivian of Oued Tidzi, one from the Barremian of Ida ou Troumma, and two from the Barremian of Tibourr’m; these resemble the more normal somewhat depressed Neocomian form of the species.
Moutonithyris dutempleana (d’Orbigny). This almost ubiquitous Albian species is recorded by both Roch and Ambroggi from both the Clansayesian and the Albian. Its occurrence in the Albian would not be surprising. Doubts are raised, however, by two circumstances: (a) M. dutempleana is very rare in the Clansayesian and known certainly from that stage only in Sardinia (Dieni et al. 1975). On the other hand if, as is likely, the species spread from south to north, it could well occur in the Clansayesian of Morocco. ( b ) Cyrtothyris middlemissi certainly occurs in both Clansayesian and Albian and is easily mistaken for M. dutempleana (Calzada 1972, p. 66). The specimen figured by Gigout (1951, pi. 13, figs. 5-8) as T. biplicata is a Concinnithyris cf. obesa.
To summarize: T. sueuri, T. collinaria, T. salevensis, T. carteroniana, and M. dutempleana have probably been misidentified by previous authors. M. moutoniana and S. sella probably do occur rarely in south-west Morocco.
Acknowledgements. I particularly thank Mr. E. F. Owen (British Museum, Natural History), Monsieur D. Pajaud and his staff at the Universite Pierre et Marie Curie, and Monsieur J-P. Thieuloy (Grenoble). I thank Mademoiselle S. Willefert (Service de la Carte Geologique du Maroc, Rabat) for her help in locating and sending to me specimens from the Roch Collection; also the Head of the Laboratoire de Geologie-Paleontologie, Universite Mohamed V, Rabat, and Monsieur G. Cogne for lending me specimens figured by Gigout. Additional specimens were lent by: Professor D. V. Ager (Swansea), Senor S. Calzada Badia (Barcelona), Monsieur Y. Champetier (Nancy), Monsieur A. Charriere (Paris), Monsieur M. Debuyser (Paris), Professor M. Durand Delga (Toulouse), Dr. W. J. Kennedy (Oxford), Monsieur E. Lanterno (Geneva), Monsieur Y. Rangheard (Besan9on), Dr. J. Remane (Neuchatel), and Monsieur Weidmann (Lausanne).
REFERENCES
ager, d. v. 1974. The western High Atlas of Morocco and their significance in the history of the North Atlantic. Proc. geol. Ass., Lond. 85, 23-41, London.
— and evamy, b. D. 1964. The geology of the southern French Jura. Ibid. 74 (for 1963), 325-355, pi. 9, London.
ambroggi, r. 1963. Etude geologique du versant meridionel du Haut Atlas occidental et de la Plaine du Souss. Notes et Mem. Serv. geol. Maroc, 157, 321 pp., 181 figs., Rabat.
MIDDLEMISS: CRETACEOUS TEREBRATULIDAE
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arkell, w. J. 1956. Jurassic Geology of the World , Edinburgh.
barczyk, w. 1969. Upper Jurassic terebratulids from the Mesozoic border of the Holy Cross Mountains in Poland. Pr. Muz. Ziemi, 14, 1-82, pis. 1-18, Warsaw.
bogdanova, t. n. and lobacheva, s. v. 1966. Neocomian Fauna of the Kopet-Daga. Min. Geol. U.S.S.R., Inst.
Econ. Sci. Leningrad, n.s. 130, 1-140, pis. 1-13, Leningrad. [In Russian.] bonneau, m., beauvais, l. and middlemiss, f. a. 1975. L’unite de Miamou (Crete-Grece) et sa macrofaune d’age Jurassique superieur (Brachiopodes, Madreporaires). Ann. Soc. geol. Nord, 94 (for 1974), 71-85, pis. 10-11, Lille.
boullier, A. 1976. Les terebratulides de VOxfordien du Jura et de la bordure sud du Bassin de Paris. Thesis, Besangon.
buckman, s. s. 1918. The Brachiopods of the Namyau Beds, northern Shan States, Burma. Pal. Indica, n.s. 3 (for 1917), Mem. no. 2, 1-254, pis. 1-21, Calcutta.
busnardo, R. and durand-delga, m. 1960. Donnees nouvelles sur le Jurassique et le Cretace inferieur dans Test des Cordilleres Betiques (Regions d’Alcoy et d’ Alicante). Bull. Soc. geol. Fr. (7), 2, 278-287, Paris.
calzada, s. 1972. Cyrtothyris middlemissi, n. sp. del Aptiense de Garraf (Barcelona). Acta geol. Hisp. 7, 66-68, 2 figs., Barcelona.
choubert, g., faure-muret, a. and hottinger, l. 1967. Apergu geologique du bassin cotier de Tarfaya. Notes Mem. Serv. geol. Maroc, 175 (1), 7-106, Rabat.
cox, Margaret m. and middlemiss, f. a. 1978. Terebratulacea from the Cretaceous Shenley Limestone.
Palaeontology, 21, 411-441, pis. 40-42, figs. 1-13, London. d’archiac, a. 1847. Rapport sur les fossiles du Tourtia. Mem. Soc. geol. Fr., (2) 2, 291-351, pis. 13-25, Paris. dieni, I., middlemiss, f. a. and owen, e. f. 1975. The Lower Cretaceous Brachiopods of east-central Sardinia.
Bol. Soc. Pal. Ital. 12 (for 1973), 166-216, pis. 32-38, Modena. geyssant, jeannine. 1966. Glossothyris et Pygope (Terebratulidae)— essai de repartition de ces especes dans la domaine mediterraneen. Notes Serv. geol. Maroc, 26, 75-98, pis. 1-3, figs. 1-7, 8 tables, Rabat. gignoux, m. 1955. Stratigraphic Geology (English edn.), San Francisco.
gigout, m. 1951. Etudes geologiques sur la Meseta marocaine occidentale (arriere-pays de Casablanca, Mazagan et Safi). Notes Mem. Serv. geol. Maroc, 86, 1-507, pis. 1-18, Rabat. imlay, R. w. 1937. Lower Neocomian fossils from the Miquihuana region, Mexico. J. Palaeont. 11, 552-574, pis. 70-83, Menasha.
— 1940. Neocomian faunas of northern Mexico. Bull. G. S. Amer. 51, 117-190, pis. 1-21, New York. kyansep, n. p. 1961 . Terebratulids of the Lusitanian Beds of the Lower Kimmeridgian of the south-west Crimea.
Akad. Nauk. U.S.S.R. 8, 1-101, 8 pis., Moscow. [In Russian.] loriol, p. de. 1866. Description de fossiles de V oolite corallienne, de Vetage valangien et de Vetage urgonien du Mont Saleve, Geneva.
1867. In favre, A. Recherches geologiques dans la Savoie, Paris and Geneva.
— 1868. Monographie des couches de l’etage valangien des Carrieres d’Arzier (Vaud). Mater, pour Paleont. suisse, ser. 4, Geneva.
— and gillieron, v. 1869. Monographie paleontologique et stratigraphique de l’etage urgonien inferieur du Landeron (Neuchatel). Mem. Soc. helv. Sc. nat. 23 (5), 1-123, pis. 1-18, Zurich.
middlemiss, F. A. 1959. English Aptian Terebratulidae. Palaeontology, 2, 94-142, pis. 15-18, London.
1968a. Brachiopodes du Cretace inferieur des Corbieres orientales (Aude). Ann. Paleont. (Invert.), 54,
173-197, pis. A-C, Paris.
1968 b. Observations on the ontogeny of the brachiopod Sellithyris sella. Bull. Ind. geol. Ass. 1, 1-17, pi. 1,
Chandigarh.
1973. The geographical distribution of Lower Cretaceous Terebratulacea in western Europe. In casey, r.
and rawson, p. f. (eds.). The boreal Lower Cretaceous: Geol. J. Spec. Issue no. 5, 1 10-129, Liverpool.
— 1976. Lower Cretaceous Terebratulidina of northern England and Germany and their geological back- ground. Geol. Jb. A30, 21-104, pis. 1-11, Hanover.
— 1979. Boreal and Tethyan brachiopods in the European early and middle Cretaceous. Kreide Europas IUGS ser. A.
muir-wood, h. M. 1965. In moore, R. c. (ed.). Treatise on Invertebrate Paleontology, pt. H, New York.
Pictet, f-j. and loriol, p. de. 1 872. Description des fossiles du terrain cretace des environs de Sainte-Croix, pt. 5. Mater. pour la Paleont. suisse (6), Geneva.
ROCH, E. 1930. Etudes geologiques dans la region meridionale du Maroc occidentale. Notes et Mem. Serv. Mines Maroc, 9, 1-542, pis. 1-26, Macon.
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Smirnova, t. n. 1960. Brachiopoda. In drushchitz, v. v. and kudriavcheva, m. p. Atlas of the Lower Cretaceous Fauna of the northern Caucasus and Crimea. Trudy, VNII Gaz., 370-387, 6 pis., Moscow. [In Russian.]
— 1969. A new terebratulid genus from the Tithonian-Valanginian. Pal. Zh., 3, 144-146, Moscow. [In Russian.]
— 1972. Brachiopods from the Crimea and northern Caucasus. Akad. Nauk. U.S.S.R. 140 pp., 13 pis., Moscow. [In Russian.]
Typescript received 5 March 1979
Revised typescript received 15 November 1979
F. A. MIDDLEMISS
Department of Geology Queen Mary College Mile End Road London
COLLIGNONICERATID AMMONITES FROM THE MID-TURONIAN OF ENGLAND AND NORTHERN FRANCE
by W. J. KENNEDY, C. W. WRIGHT, and J. M. HANCOCK
Abstract. Collignoniceras Breistroffer, 1947 is represented by five species in the mid-Turonian of England and Touraine (the type area of the Turonian stage) in northern France. The cosmopolitan and highly variable type species C. woollgari (Mantell) is shown to be a senior synonym of C. schlueterianum (Laube and Bruder) and C. mexicanum (Bose) amongst others, and shows features indicating that Selwynoceras Warren and Stelck, 1940 (the type species of which S. boreale (Warren), is also redescribed) is a synonym of Collignoniceras sensu stricto. Other species referred to the genus are C. carolinum (d’Orbigny), C. papale (d’Orbigny), C. canthus (Sornay) and C. turoniense (Sornay). Ammonites fleuriausianus d’Orbigny, 1841 is a senior synonym of A. vielbancii d’Orbigny, 1850 and is made the type species of Lecointriceras gen. nov., to which two further species, L. carinatum sp. nov. and L. costatum sp. nov. are also referred.
Collignoniceras woollgari (Mantell) is one of the most widely cited mid-Cretaceous ammonite species, giving its name to the middle zone of the Turonian standard sequence (Wright in Arkell et al. 1957; Rawson et al. 1978). As with other classic species, the type material has never been adequately figured and is of uncertain horizon, although it has at least survived the vicissitudes of a century and a half since its original description (Mantell 1822, p. 197; pi. 21, fig. 16; pi. 22, fig. 7). In England, where it was first described, the species is rare and the lectotype remains the only good adult specimen known. Elsewhere, however, it is recorded abundantly, especially in the U.S. Western Interior region, where it formed the basis of one of the early accounts of intraspecific variability in Cretaceous ammonites (Haas 1946), although as Haas and Meek before him (1876, p. 455) noted, authors have questioned whether the great majority of specimens referred to this cosmopolitan species are indeed conspecific with Mantell’s types.
We have studied hundreds of European, American and Japanese Collignoniceras in connection with this project, and encountered an initially bewildering range of variation, both in adult ornament and the size at which ontogenetic changes occur. We have relatively few juveniles from Europe but many from the U.S. A.; conversely, large complete adults are common in European collections, but those from the U.S. are usually fragmentary. Whilst it would be possible to select individuals with differences that could be framed into diagnostic features for specific or subspecific separation, this would be misleading and conceal the over-all common features of the species recognized below. In C. woollgari in particular we have no doubt that a series of local races of the species existed over its wide spread, but to separate formally the successive or local populations, differing in the extent of morphological variation but overlapping, would serve no useful purpose. The broad, variable species described below not only represent reality but are adequate for detailed correlation and discussion of the evolution of the genus.
SYSTEMATIC DESCRIPTIONS
Location of specimens. The following abbreviations are used to indicate the repositories of specimens studied: AM Museum de Paleontologie d’Angers.
BMNH British Museum (Natural History), London.
CS Chateau de Saumur
EMP Ecole des Mines, Paris (now housed at the Universite Claude Bernard, Lyon).
IPalaeontology, Vol. 23, Part 3, 1980, pp. 557-603, pis. 62-77.|
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FSM Faculte des Sciences, Le Mans; chiefly collections formerly housed in the Musee de Tesse, Le Mans. FSR Institut de Geologie, Universite de Rennes.
GK Department of Geology, Kyushu University, Fukuoka.
MNHP Museum National d’Histoire Naturelle, Paris.
OUM University Museum, Oxford; unless stated otherwise, these are collections made by Hancock and Kennedy.
SP Collections of the Sorbonne, now Universite de Paris VI.
WW C. W. and E. V. Wright collection.
Dimensions. All dimensions are given in millimetres; figures in parentheses are the dimensions as a percentage of the total diameter. D = diameter; Wb = whorl breadth; Wh = whorl height; U = umbilicus; Ic = intercostal; c = costal; R = number of ribs per whorl.
Suture terminology. The suture terminology of Wedekind (1916; see Kullman and Wiedmann 1970 for a recent review) is followed here: I = Internal lobe, U = Umbilical lobe, L = Lateral lobe, E = External lobe.
Suborder ammonitina Hyatt, 1889 Superfamily acanthocerataceae de Grossouvre, 1 894 [nom transl. et correct. Hyatt 1900, ex Acanthoceratides de Grossouvre, 1894]
Family collignoniceratidae Wright and Wright, 1951 Subfamily collignoniceratinae Wright and Wright, 1951 Genus collignoniceras Breistroffer, 1947 {non Van Hoepen, 1955)
Type species. Ammonites woollgari Mantell, 1822 by the original designation of Meek (1876) as type species of Prionotropis Meek, 1876 {non Fieber, 1853), for which Breistroffer (1947) proposed Collignoniceras as nomen novum.
Diagnosis. Medium to large, moderately involute to evolute ammonites. Early whorls compressed, parallel sided, ornamented by crowded or sparse, prorsiradiate, straight or flexuous ribs, mostly long, with weak to strong umbilical bullae. All ribs bear in the early stages outer ventrolateral tubercles in addition to siphonal clavi.
This style of ornament is, in some species, retained to maturity. In most, however, the ribs coarsen, become widely spaced, with strong to weak umbilical tubercles (which migrate progressively outwards from the umbilical margin), prominent inner and outer ventrolateral tubercles which may fuse into a massive horn or flared rib, from which commonly arise pairs of low ribs, joining siphonal clavi more numerous than the ventrolateral and linked into a more or less continuous keel. Rarely the ornament is greatly reduced on the body whorl.
The sutures are little incised, with massive saddles.
Discussion. The diagnosis given above summarizes the rather wide variation seen in species referred to this genus, which include C. boreale (Warren), C. papale (d’Orbigny), C. canthus (Sornay), C. turoniense (Sornay) and C. carolinum (d’Orbigny). The nomenclatorial history of the genus is somewhat complex. Meek introduced a subgenus Prionotropis in 1876, with Ammonites woollgari Mantell as type species. Breistroffer (1947) pointed out the prior usage of Prionotropis by Fieber (1853) and proposed Collignoniceras as nomen novum. Meanwhile Warren and Stelck (1940) had proposed the genus Selwynoceras with P. borealis Warren, 1930 as type species, distinguishing it from Meek’s Prionotropis by the presence of a row of nodes instead of a keel on the inner whorls and the marked alternation in length and strength of the ribs. Wright (in Arkell et al. 1957, p. L426) regarded Selwynoceras as a subgenus of Collignoniceras , whilst Powell (1963, p. 1223) considered the two synonymous. Following an application by Matsumoto and Wright in 1966, the International Commission on Zoological Nomenclature ruled in 1968 (Opinion 861) that Collignoniceras Breistroffer, 1947, should be given priority over Selwynoceras Warren and Stelck, 1940, by those who regard the two as synonyms.
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From a comparison of the types and other specimens of C. woollgari and S. bore ale, we would agree with Powell that the two do not bear even subgeneric separation: boreale is simply a small species of Collignoniceras in which the flared ribs appear at a relatively early stage. The ventral tuberculation visible on the outer whorl of the lectotype (here designated), which is refigured here as PI. 70, figs. 1 -2, is on exactly the same plan as in English woollgari, whilst, as Haas (1946), Powell (1963) and Matsumoto (1965) have shown, the style of ribbing of juvenile Collignoniceras is very variable.
Collignoniceras differs from Prionocyclus Meek, 1876 (type species P. wyomingensis Meek) in that the latter has very fine dense irregular ribs through most or all of its ontogeny and a broader venter with an entire or serrated keel. C. woollgari and P. hyatti (Stanton) overlap in time in the southern U.S. and some late C. woollgari there and also in Europe show a low siphonal keel at maturity, emphasizing the intimate relationship between the two. Ribbing is usually dominant over tuberculation in Prionocyclus, although some species bear finger-like ventrolateral spines, fore- shadowing the development seen in the later Prionocycloceras (Young 1963, pi. 23, figs. 1-6; pi. 27, figs. 2-4). Matsumoto (1965, p. 19) discusses other differences between these two genera.
Subprionocyclus Shimizu, 1932 was originally separated from Collignoniceras [Prionotropis] on the basis of minor differences between the internal sutures. As Matsumoto (1959, p. 109) notes, however, distinguishing features also include the paired or alternately long and short sigmoidal ribs of Subprionocyclus which may flatten on the outer whorl, greater persistence of outer ventrolateral tubercles and absence of massive horns. Like Prionocyclus, Subprionocyclus has a continuous persistent keel which varies with the density of the ribbing from finely to coarsely serrate.
Germariceras Breistroffer, 1947 is perhaps only doubtfully separable from Prionocyclus', known only from juveniles, it may be separated from Collignoniceras by the possession of fine dense narrow ribs with small sharp umbilical, inner and outer ventrolateral tubercles and a finely serrated continuous keel with more serrations than the number of ventrolateral tubercles.
Reesidites Wright and Matsumoto, 1964, which should perhaps be placed in Barroisiceratinae, is compressed and involute, high whorled, with a fastigiate venter; sinuous ribs branch in groups of two or three from small umbilical bullae, with single ventrolateral and siphonal clavi only. The largest individuals barely exceed 100 mm diameter (Matsumoto 1965).
Subprionotropis Basse, 1950, known only from specimens a few centimetres in diameter, differs from Collignoniceras in being involute with compressed whorls, with ribs arising in pairs from umbilical bullae (with additional intercalated ribs) bearing only ventrolateral and siphonal clavi and forming strong chevrons on the fastigiate venter. At the end of the body chamber, ribs and tubercles weaken and the venter becomes rounded.
Lymaniceras Matsumoto, 1965 and Niceforoceras Basse, 1948 are both compressed and involute, with weak, dense flexuous ribs or striae, a single ventrolateral tubercle and a finely serrated keel.
Collignoniceras is the earliest genus of Collignoniceratidae to appear in the Turonian, and, as Matsumoto (1965) has noted, some individuals in variable United States Western Interior populations show early whorls which foreshadow Prionocyclus, Subprionocyclus and thence the remaining late members of the group.
With respect to the evolutionary origins of the genus, Wright (in Arkell et al. 1957, p. L426) and Matsumoto (1965, p. 10) have suggested that the diminutive late Cenomanian acanthoceratinid Protacanthoceras Spath, 1923 might be the ultimate ancestor, with Neocar diocer as Spath, 1926 as an intermediate. Recent collecting from the latest Cenomanian/early Turonian faunas of the condensed Neocar diocer as Pebble Bed of Devon (see Hancock, Kennedy and Wright 1977, fig. 2 for details) has now produced a range of specimens that provisionally we refer to Thomelites Wright and Kennedy, 1973, among which are individuals with siphonal clavi tending to form a continuous serrated keel. In addition, a few poorly preserved fragments seem already to have reached the stage of Collignoniceras in some features of decoration. There remains, however, a gap in the European successions, corresponding to most of the Mammites nodosoides assemblage Zone, in which the genus is absent apart from a single possible example in the collection of Colonel O. H. Bayliss, from Shapwick, Devon; W. A. Cobban (in litt., 1978) tells us that Collignoniceras appears at the top of the North American correlatives of this zone.
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Occurrence. Collignoniceras is widespread in the middle of the Turonian stage, the classic woollgari Zone. There are records from England, France, Germany, Czechoslovakia, Poland, Rumania, Turkestan, Japan, California, Texas, the U.S. and Canadian Interiors, Greenland, north Africa, Colombia, and northern Australia.
Collignoniceras woollgari (Mantell)
Plates 62-67 ; Plate 69, figs. 3-4; Plate 71, figs. 1-3; text-figs. 1a, 2-4
1822 non 1841 1850 1855 1860 1867 1872 1872 1872
1887
1887
1902
1902
1902
1907
1925
1928
1931
1931
1931
1946
1963
1971
1972
1975
1977
1977
Ammonites Woollgari Mantell, p. 197, pi. 21, fig. 16; pi. 22, fig. 7.
Ammonites Woollgari Mantell; d’Orbigny, p. 352, pi. 108, figs. 1-3.
Ammonites Woolgarii d’Orbigny, p. 189 (pars).
Ammonites Woollgari Mantell; Sharpe, p. 27, pi. 11, figs. 1, 2.
Ammonites carolinus (d’Orbigny); Courtiller, p. 251, pi. 3, fig. 2.
Ammonites Woolgarii Mantell; Courtiller, p. 7, pi. 8, figs. 1-4.
Ammonites Woolgari Mantell; Schliiter, p. 25, pi. 9, figs. 1-5; non pi. 12, figs. 5, 6. Ammonites Woollgari Mantell; Geinitz, p. 184, pi. 33, figs. 1, 2 (?), non 4-5.
Ammonites Woolgari Fritsch, p. 30 (pars), pi. 3, figs. 1-3; pi. 4, figs. 1-2; pi. 14, fig. 6; non pi. 2, tigs. 1-2; pi. 15, fig. 6.
Acanthoceras Woollgari (Mantell); Laube and Bruder, p. 235, text-fig.
Acanthoceras Schliiterianum Laube and Bruder, p. 236, pi. 29, figs. 2-3.
Acanthoceras Woollgari (Mantell); Petrascheck, p. 149, text-figs. 7-8.
Acanthoceras cfr. Woollgari (Mantell); Petrascheck, p. 148, pi. 12, figs. 2-3.
Acanthoceras Schliiterianum Laube and Bruder; Petrascheck, p. 150, pi. 10, fig. 3; pi. 11, fig. 3; pi. 12, fig. 1.
Prionotropis Schliiterianum Laube and Bruder; Pervinquiere, p. 275.
Prionotropis Schliiteriana Laube and Bruder; Diener, p. 156.
Prionotropis woollgari Mantell var. mexicana Bose, p. 262, pi. 1 1, figs. 11, 12. Pseudaspidoceras(l) chispaense Adkins, p. 51, pi. 3, figs. 1-2.
Pseudaspidocerasl sp. Adkins, p. 53, pi. 2, fig. 2.
Pseudaspidoceras(l) n.sp. A; Adkins, p. 53, pi. 3, figs. 3-4.
Prionotropis woollgari Meek (? non Mantell); Haas, p. 150, pis. 11, 12; pi. 13, figs. 1-3, 5-18; pi. 14, figs. 1-10, 12-16; pi. 15, figs. 1-6, 9, 10; pis. 16, 17; pi. 18, figs. 1-2, 7-9; text-figs. 1-91. Selwynoceras mexicanum (Bose); Powell, p. 1225, pi. 166, figs. 2-7; pi. 167, figs. 1, 3-8; pi. 168, fig. 4; text-figs. 2-4.
Collignoniceras woollgari (Mantell); Matsumoto, p. 130, pi. 21, fig. 4, text-fig. 1. Collignoniceras woollgari (Mantell); Cobban and Scott, p. 94, pi. 14, fig. 5; pi. 30, fig. 1; pi. 37, figs. 9-10 (with additional synonymy).
Collignoniceras woollgari (Mantell); Hattin, pi. 10, figs. N, P, Q, R.
Collignoniceras (Selwynoceras) schlueterianum (Laube and Bruder); Hancock, Kennedy and Wright, p. 156.
Collignoniceras (Collignoniceras) cf. C. woollgari sensu Matsumoto, 1965, group E; Hancock, Kennedy and Wright, p. 156.
Types. The lectotype, designated by Wright and Wright (1951, p. 35), is BMNH 5682, from the Middle Chalk of Lewes, Sussex, refigured here as Plate 62, figs. 1-2; Plate 63, fig. 9. Two additional specimens from Mantell’s collection, BMNH C5742 a-b (Plate 69, figs. 3, 4), are presumed to be paralectotypes.
Other specimens studied. These include: BMNH 4863 a-b, from the Middle Chalk ‘near Lewes, Sussex’; BMNH 43963 ‘Lower Chalk, near Lewes’ (J. de C. Sowerby Collection); BMNH C30394 ‘Turonian Mount Caburn Pit, near Glynde, Sussex’ (labelled aff. woollgari by L. F. Spath); BMNH C40152 from the Middle Chalk, Terebratulina lata Zone, Mickleham Bypass, Surrey (C. W. and E. V. Wright Collection); WW 16682, 14792-4, from the Middle Chalk, top of the T. lata Zone Middle Chalk, Mickleham Bypass, Surrey; WW 22925-7, Middle
EXPLANATION OF PLATE 62
Figs. 1 -2. Collignoniceras woollgari (Mantell). The lectotype, BMNH 5682, from the Middle Chalk of Lewes, Sussex.
PLATE 62
KENNEDY, wright and Hancock, Collignoniceratid ammonites
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Chalk, Lewknor Crossroads, Lewknor, Oxon. (ex R. E. H. Reid Collection); OUM K 10273, K 10275-76 from no more than 5 m below the top of the Chalk Rock at Fognam Barn, Berkshire, 3 km WNW of Lambourn.
BMNH 88988 b, 88989 a-c from the Turonian of the White Mountain, near Prague, Czechoslovakia.
French specimens include the following: OUM KZ 741, 743-4, 746, 748-9, 753, from the St. Cyr-en-Bourg Fossil Bed, Champignonniere Les Rochains, 7 km south of Saumur and north-east of Montreuil-Bellay, Maine- et-Loire, and numerous specimens in the Museum de Paleontologie, Angers, from this bed and adjacent levels in the Tuffeau Blanc (Couffon Collection etc.) variously labelled Saumoussay, St. Cyr-en-Bourg, Saumur, and elsewhere, including AM 57, AM 59, AM 116.
There are numerous specimens from Ponce, Sarthe, and others from Bourre in the Cher Valley, Loir-et-Cher, including BMNH C74803.
Dimensions
|
D |
Wb |
Wh |
Wb: Wh |
U |
Ribs |
|
|
Lectotype |
130(100) |
40 (31) |
40 (31) |
1 |
50 (38) |
13 |
|
FSR, C273 |
67-3 (100) |
20-4 (30) |
25-0 (37) |
0-81 |
23-9 (36) |
24 |
|
MNHP W7 |
58-5 (100) |
21-0 (36) |
-(-) |
— |
22-8 (39) |
19 |
|
MNHPW18 |
61-0(100) |
24-0 (39) |
23-7 (39) |
101 |
22-0 (36) |
22 |
|
MNHP X’ |
86-0 (100) |
29-0 (34) |
34-9 (41) |
0-83 |
29-5 (34) |
~20 |
|
MNHPW15 |
81-0(100) |
32-0 (40) |
32-0 (40) |
1-0 |
27-8 (34) |
19 |
|
MNHPIc |
141-0(100) |
52-0 (37) |
49-5 (35) |
1-05 |
55 (39) |
— |
|
Ic MNHP 6778 MNHPW20 |
133-0(100) |
41-5(29) 45-0 (34) |
49- 5 (35) 50- 0 (38) |
0-83 0-9 |
44-5 (33) |
18 |
|
Ic |
162-0(100) |
55-0 (34) |
52-0 (32) |
1-05 |
67 (41) |
— |
|
MNHP W4 c |
137-0(100) |
60-0 (43) |
51-0(37) |
1-18 |
- (-) |
15/16 |
|
Ic |
39-5 (29) |
39-5 (29) |
1-0 |
|||
|
MNHP W10 |
109.0(100) |
47-5 (44) |
42-0 (39) |
M3 |
37-0 (34) |
— |
|
33-5(31) |
38-8 (36) |
0-86 |
||||
|
MNHPW19 |
175-0(100) |
74-8 (43) |
65-0 (37) |
1-15 |
65-0 (37) |
15 |
Description. The inner whorls of our smallest specimens show coiling to have been moderately evolute, with compressed whorls and a shallow umbilicus. At about 10-15 mm diameter, there are 27-32 ribs per whorl; the density decreases with increasing size. The ribs are even, bar-like, prorsiradiate, straight and clearly demarcated from the flat interspaces. As size increases, ribs become much more widely spaced; at 40-50 mm diameter there are only 17-24 ribs per whorl. They are of variable strength, arise from weak to strong umbilical bullae and are narrow, high and separated by wide, flat interspaces; they are markedly prorsiradiate and straight to concave on the flanks, always single, with no intercalated ribs. At the ventrolateral shoulder they bear conical to feebly clavate inner ventrolateral tubercles. From these the ribs are