S H A R K S , R A Y S A N D A C H I M A E R O I D F R O M T H E
K I M M E R I D G I A N ( L A T E J U R A S S I C ) O F R I N G S T E A D ,
S O U T H E R N E N G L A N D
by C H A R L I E J . U N D E R W O O D
ABSTRACT. Sampling of a lenticular concentration of vertebrate debris and associated sediments from the lower
Kimmeridgian of southern England has allowed the study of a diverse and abundant assemblage of chondrichthyan
remains. A number of previously undescribed species are recorded, of which three new species are named; Squatina?
frequens, Synechodus plicatus and Protospinax planus. Additional diagnosis of the genus Paracestracion Koken is
given to allow its identification from dental remains. Several nominal batoid species are synonymised with Spathobatis
bugesiacus Thiolliere. This assemblage is considered to be typical of Middle–Late Jurassic neritic environments, and
is compared to other contemporaneous selachian faunas.
KEY WORDS: chimaeroid, Dorset, Jurassic, Kimmeridgian, ray, shark.
R E C O R D S of fossil sharks and rays from the Jurassic have largely been restricted to descriptions of
material preserved as entire skeletons or isolated teeth and fin spines of large species. Few studies have
concentrated on the isolated teeth of smaller taxa, with this work generally being incomplete in its
coverage of faunas (e.g. Thies 1983; Candoni 1993; Thies and Candoni 1998). Despite this poor systematic
coverage, it is evident that the Jurassic represented a major period of radiation of the Neoselachii, with
many extant groups being present by the end of the period.
G E O L O G I C A L S E T T I N G
Upper Jurassic sediments are well exposed along the coast of Dorset, southern England. At Ringstead
village, Oxfordian sandstones, limestones and mudstones of the Corallian Group are overlain by
Kimmeridgian mudstones of the Kimmeridge Clay (Text-figs 1–2). A minor basal Kimmeridgian hiatus
(Wignall 1990a) is succeeded by dominantly sandy and shelly clays, which pass upward into the laminated
neritic mudstones typical of most of the unit. This basal interval is best included in the Kimmeridge Clay on
lithological (first appearance of laminated black mudstones) and historical grounds; the recent inclusion of
this interval in the Corallian Group (Newell 2000) is considered here as unnecessary and misleading.
Within the cymodoce Zone, two laterally continuous muddy sandstones, the Wyke and Black Head
siltstones, are present. These sandstones are intensely bioturbated and both have an erosive base. This is
especially evident within the Black Head Siltstone, where an underlying unit of black mudstone is seen to
be cut out over the width of the exposure. Between these two coarser units, a lenticular horizon of shelly
sandstone with numerous reworked phosphate granules records the presence of a third erosion surface.
Where intervening sediment had been eroded, this bed was seen to become incorporated into the base of
the Black Head Siltstone. The sedimentary architecture is therefore considerably more complicated than
the single erosion surface noted by Newell (2000).
M A T E R I A L A N D M E T H O D S
The bulk of the vertebrate material studied was extracted from a lenticular calcareous sandstone between
the Wyke and Black Head siltstones, in places being incorporated into the base of the latter. This lens is up
[Palaeontology, Vol. 45, Part 2, 2002, pp. 297–325, 4 pls] q The Palaeontological Association

to 5 cm thick, contains abundant oysters as well as a diverse fauna of other molluscs, and is extremely rich
in small granules of reworked phosphate. Most of the material studied came from an exposure immediately
to the east of the caravan site at Ringstead. This exposure has subsequently been obscured by sea-defences
and steps. A second occurrence of the lens was recognised immediately to the east of the present end of the
sea-defences in the autumn of 1998, but was subsequently removed by storm erosion. It is possible that
future erosion will reveal more exposures of this lens. Further samples were collected from the
immediately underlying mudstone, although it is likely that many of the teeth obtained from this unit
came from burrow fills originating from above. A lens of shell material from immediately below the Wyke
Siltstone was also sampled, as was the sandy mudstone from the base of the Kimmeridge Clay. Several
other phosphate-bearing levels within sandstones of the Kimmeridge Clay and the upper part of the
Corallian Group at nearby exposures at Black Head were sampled, but proved to contain very few
selachian remains or to be cemented with pyrite or quartz. About 25 kg of the lenticular sandstone was
sampled, along with between 12 and 40 kg of each of the mudstone levels. Only very small trial samples
were processed of other sandstones.
Some comparative material was studied from the Kimmeridge Clay of Small Mouth Sands in Portland
Harbour. This is a well-known vertebrate site, with abundant chondrichthyan material (Dineley and
Metcalf 1999, p. 405). Most of the fossils are found loose on the beach or by sieving beach sand below a
vegetated and slipped slope. For this reason, material is only very loosely constrained stratigraphically in
comparison to that from Ringstead, although it is probable that fossils originate from the same general
stratigraphic interval. In addition to the taxa recorded in this study, other hybodont sharks, chimaeroids and
actinopterygians have previously been recorded from this site (Dineley and Metcalf 1999, p. 405;
Brockenshire, pers. comm. 1999).
The preservation of selachian material from the main sampled lens and the underlying mudstone is
similar, with two distinct modes of preservation of the teeth being evident. Many teeth have either no root,
or have it preserved as a pale and highly porous remnant. In all teeth studied in detail this is seen to be a
result of intense boring by endolithic organisms (see Underwood et al. 1999a) and not due to incomplete
development of the teeth. In other specimens, the root is black and smooth, with the foramina often filled
with dark material. It is possible that the latter teeth, with secondary phosphate precipitated over the root,
have been reworked alongside the other reworked phosphate nodules and phosphatised shell material. At
least some of this material may have been transported from a shallower setting, as suggested by the
presence of fragments of colonial corals and phosphatised oolitic sediment. Despite this probable
reworking and transport, there is no evidence for strong abrasion of any of the material. Many teeth
have become highly fractured after burial, with calcite cement filling the cracks. Removal of this cement
298 P A L A E O N T O L O G Y , V O L U M E 4 5
TEXT–FIG. 1. Map showing the locations of sites at Ringstead, Black Head and Small Mouth Sands.

U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 299
TEXT-FIG. 2. Stratigraphical succession at Ringstead showing the occurrences of chondrichthyan and other fish remains;
vertical scale in metres.

during acid preparation has resulted in the breakage of a large proportion of specimens. Teeth with
secondary phosphate were rarely observed within other samples. Much of the vertebrate material from the
basal Kimmeridge Clay has been highly abraded suggesting considerable reworking.
In all studied samples, selachian material was less abundant than teeth, vertebrae and other bones of
actinopterygian fish. Isolated teeth suggest that diverse actinopterygian faunas are present, containing the
same general groups as those noted by Mudroch and Thies (1996) from the Kimmeridgian of Germany. No
reptile material was recorded from Ringstead despite the relative abundance of reptile fossils at Small
Mouth Sands.
Calcareous sandstones were dissolved in buffered 20 per cent acetic acid, with frequent removal of acid-
extracted fossils to limit the dissolution of calcite cements within fractures. Mudstones were oven dried
before being hand-sieved at 125 mm, the resulting residue then being placed in 10 per cent acetic acid to
remove the majority of the shell material. Samples were then sorted and picked from size fractions down to
355 mm. Selachian material never comprised a major part of the resulting residue because of the high
relative abundance of grains of phosphate and quartz, pyrite and actinopterygian vertebrae.
Figured specimens were coated with gold-palladium alloy and observed with a scanning electron
microscope (SEM). All figured specimens are deposited in the Department of Palaeontology at The
Natural History Museum, London.
S Y S T E M A T I C P A L A E O N T O L O G Y
The terminology used here for parts of the selachian teeth follows that of Cappetta (1987), with the nomenclature of the
chimaeroid material following Patterson (1965) and Duffin and Reynders (1994). Synonymies given generally only
include works that figure or mention teeth or other material that can be directly compared to specimens described here.
Taxonomic relationships of the Neoselachii largely follow the work of Shirai (1996), with the placing of Synechodus
within the Squalea following Duffin and Ward (1993), who suggested a close affinity with the Hexanchiformes.
Cohort EUSELACHII Hay, 1902
Superfamily HYBODONTOIDEA Owen, 1846
Family HYBODONTIDAE Owen, 1846
Genus ‘HYBODUS’ Agassiz, 1837
Type species. Hybodus reticulatus Agassiz 1837 from the Lower Jurassic of southern England.
Remarks. The genus Hybodus has been used to accommodate a large number of species, with only a small
proportion having a similar dentition to H. reticulatus. It is, therefore, probable that few of these species
should be included in Hybodus, but the genus is retained for the species figured here until a taxonomic
revision is undertaken.
300 P A L A E O N T O L O G Y , V O L U M E 4 5
E X P L A N A T I O N O F P L A T E 1
All specimens from lens between Wyke and Black Head siltstones unless stated otherwise.
Fig. 1. ‘Hybodus’ sp. 1, P. 65670, labial view, preserved height 7·6 mm; · 7·5.
Fig. 2. ‘Hybodus’ sp. 2, P. 65671, labial view, preserved width 10 mm; · 5·5.
Figs 3–4. ‘Hybodus’ obtusus Agassiz, 1843. 3, P. 65673, partial lateral tooth of juvenile, labial view, preserved width
1·7 mm; · 36. 4, P. 65672, partial anterior tooth of juvenile, labial view, preserved height 1·5 mm; · 26.
Figs 5–8. Palaeoscyllium formosum Wagner, 1857, P. 65675, anterior tooth, height 1·6 mm; · 32·5. 5, labial view. 6,
lateral view. 7, lingual view. 8, P. 65676, lateral tooth, labial view, height 1·4 mm; · 41.
Figs 9–10. Pseudospinax sp., P. 65678, base of Kimmeridge Clay, width 1·1 mm; 9, labial view. 10, lateral view; · 41.
Fig. 11. Cantioscyllium sp., P. 65677, base of Kimmeridge Clay, labial view, width 0·9 mm; · 55.
Fig. 12. Orectolobiforme gen. et sp. indet., P. 65679, base of Kimmeridge Clay, labial view, height 1·5 mm; · 41.

P L A T E 1
UNDERWOOD, Jurassic sharks

‘Hybodus’ sp. 1
Plate 1, figure 1; Text-figure 3B–D
?1871 Hybodus grossiconus Agassiz; Phillips, p. 307, figs 19–20.
Material. One incomplete crown P. 65670; also P. 65680 from Small Mouth Sands.
Description. The single cusp is high and relatively slender and somewhat compressed. A well-developed cutting edge
continues over the cusp (except for the broken apex) and along the single preserved lateral blade. The lateral blade is
short and tapers sharply. Ornament is restricted to the lower part of both labial and lingual faces of the tooth. On the
labial face this consists of fine, regularly spaced, longitudinal folds, which do not reach the base of the crown. Some of
these folds bifurcate. Similar folds on the lingual face are finer. The root is unknown.
Remarks. This species is similar to ‘H’. grossiconus Agassiz, 1843, ‘H’. sp (of Schaeffer and Patterson
1984) and ‘H’. ensis Woodward, 1916, being separated from them by the regular and widely spaced
ornament and the absence of lateral cusplets.
Occurrence. Lens between Wyke and Black Head siltstones. Teeth of this morphology are relatively common at Small
Mouth Sands.
‘Hybodus’ sp. 2
Plate 1, figure 2
1995 Hybodus sp. Candoni p. 39.
Material. Four partial teeth including P. 65671.
Description. A robust main cusp is flanked by at least one pair of small lateral cusplets, all of which are strongly
compressed. A cutting edge is very well developed, especially on lateral cusplets. The labial face of the main cusp is
ornamented with fine longitudinal folds, which were not observed to extend to the apex. Individual folds are relatively
discontinuous and bifurcation is rare. These folds are stronger and more continuous on lateral cusplets, where they may
reach the apex. The lingual face of the main cusp has finer and more continuous folds, whilst ornament on both faces of
the lateral cusplets is similar. The root is unknown.
Remarks. The overall profile of the tooth is very similar to that of ‘H.’ ensis Woodward, 1916, although
differs from it in the possession of strong ornament on the lateral cusplets. It is possible that ‘Hybodus’ sp.
1 and ‘Hybodus’ sp. 2 are synonymous, the difference in ornament being within the range observed within
other hybodont species (Maisey 1983). It is considered here, however, that these morphologies are likely to
represent different taxa, as no intermediate forms were observed and they have very different relative
frequencies at the different sites studied.
Occurrence. Ringstead Coral Bed and lens between Wyke and Black Head siltstones.
‘Hybodus’ obtusus Agassiz, 1843
Plate 1, figures 3–4; Text-figure 3A
1843 Hybodus obtusus Agassiz, p. 186, pl. 23, figs 43–44.
1889 Hybodus obtusus Agassiz; Woodward, p. 272, pl. 11, figs 8–13.
1991 Hybodus obtusus Agassiz; Martill, p. 197, pl. 36, fig. 8.
1995 ‘Polyacrodus’ obtusus (Agassiz); Candoni, p. 39, figs 1–2.
Material. Fragments of at least 20 teeth including P. 65672; also P. 65674 from Small Mouth Sands.
Description. Fragments of teeth of a wide size range were recovered, but the overall similarity suggests that little
heterodonty was present. The main cusp is rather low and triangular in profile, with 2–3 pairs of rather widely spaced
302 P A L A E O N T O L O G Y , V O L U M E 4 5

lateral cusplets decreasing in size laterally. The cusps are slightly compressed, with a very well-developed cutting
edge, which continues unbroken over the occlusal edge. Strong and sharp-edged folds are present on the labial face of
the cusps of most teeth. These bifurcate irregularly towards the base of smaller teeth, but only rarely divide in larger
teeth. A well-developed fold covers a pronounced labial keel on the main cusp. These folds are widely spaced and
reach the cusp apex in small teeth, becoming more numerous but less well developed in larger teeth. Similar but less
well-developed folds are present on the lingual face. In the largest teeth (only seen as small fragments in this study), the
folds may be partly lost and small swellings may be present at the base of the labial face of the tooth.
Remarks. ‘Hybodus’ obtusus is well known from many Callovian–Kimmeridgian localities in northern
Europe (e.g. Woodward 1889; Martill 1991).
Occurrence. Present in most samples. Teeth of ‘H.’ obtusus are common at Small Mouth Sands.
Subcohort NEOSELACHII Compagno, 1977
Superorder GALEA Shirai, 1996
Order CARCHARHINIFORMES Compagno, 1977
Family SCYLIORHINIDAE Gill, 1862
Genus PALAEOSCYLLIUM Wagner, 1857, non Marck, 1863.
Type species. Palaeoscyllium formosum Wagner, 1857 from the Upper Jurassic of Germany.
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 303
TEXT-FIG. 3. A, ‘Hybodus’ obtusus Agassiz, 1843; P. 65674, Small Mouth Sands, lateral tooth, labial view. B–D,
‘Hybodus’ sp. 1; P. 65680, Small Mouth Sands. B, labial view. C, lateral view. D, lingual view.

Palaeoscyllium formosum Wagner, 1857
Plate 1, figures 5–8
1857 Palaeoscyllium formosum Wagner, p. 291.
1993 Parasymbolus octevillensis Candoni, pp. 148–155, text-figs 1–2, pls 1–3.
1994 Parasymbolus octevillensis Candoni; Candoni, pp. 48–52, figs 1–2, pl. 1–3.
1995 Parasymbolus octevillensis Candoni; Candoni, p. 38, figs 1–2.
1999 Palaeoscyllium formosum Wagner; Leidner and Thies, p. 34, figs 2B, 3F.
Material. 129 entire and partial teeth including P. 65675–65676.
Remarks. The specimens recorded here do not differ from material described in detail from the
Kimmeridgian of northern France (Candoni 1993), and provide no additional taxonomic information. It
has been shown (Leidner and Thies 1999) that the isolated teeth described by Candoni (1993) as
Parasymbolus octevillensis are the same as those extracted from articulated skeletons of Palaeoscyllium
formosum from German lithographic limestones. This indicated that the two species are conspecific
and Parasymbolus is the junior synonym of Palaeoscyllium. Parasymbolus reticularis Underwood
and Mitchell, 1999 from the Cretaceous of northern England should, therefore, also be referred to
Palaeoscyllium.
Occurrence. Between Wyke and Black Head siltstones; also present but rare at Small Mouth Sands.
Order ORECTOLOBIFORMES Applegate, 1972
Incertae familiae
Genus CANTIOSCYLLIUM Woodward, 1889
Type species. Cantioscyllium decipiens Woodward, 1889 from the Upper Cretaceous of southern England.
Cantioscyllium sp.
Plate 1, figure 11
Material. One partial tooth P. 65677.
Description. The sole tooth appears to be from a posterior position in the jaw. The labial face of the crown is as wide as
high, with a smooth semicircular basal edge. The occlusal edge has a triangular main cusp, about as wide as high.
There are three poorly defined lateral cusplets, two to the anterior and one to the posterior. These are strongly flattened
and appear to be outgrowths of the occlusal cutting edge. The labial surface is ornamented by a small number of short
but strong folds. These appear to radiate from the base of the main cusp. The lingual face of the crown is
unornamented, with a poorly defined uvula.
Remarks. Cantioscyllium is known from a number of species ranging from the Barremian (Kriwet 1999) to
Campanian (Cappetta and Case 1999). This specimen allows the stratigraphical range of the genus to be
extended into the Jurassic.
Occurrence. Base of Kimmeridge Clay.
Family HEMISCYLLIDAE Gill, 1862
Genus PSEUDOSPINAX Mu
¨
ller and Diedrich, 1991
Type species. Pseudospinax pusillus Mu¨ller and Diedrich, 1991 from the Upper Cretaceous of northern Germany.
304 P A L A E O N T O L O G Y , V O L U M E 4 5

Pseudospinax sp.
Plate 1, figures 9–10
Material. Single tooth lacking root P. 65678.
Description. The crown is thin and unornamented, and has an oval labial face, which is slightly expanded laterally. A
single slender cusp projects lingually from the posterior part of the occlusal edge. A well-developed cutting surface is
present either side of the cusp, being continuous over it. Posterior to the cusp this forms an incipient cusplet. The
occlusal edge of the crown, and to a lesser extent the cusp, are angled labially to give a strongly concave crown surface.
The lingual face of the crown is smooth and is slightly expanded to form a very weak uvula below the cusp.
Remarks. This species differs from P. muftius (Thies, 1983) in lacking lateral cusplets and having a labially
projecting occlusal edge. This angled edge and the elongate cusp separate this species from P. heterodon
Underwood and Mitchell, 1999, which it otherwise strongly resembles. The general form of the tooth
crown is very similar to that of the extant torpedo ray Benthobatis (see Cappetta 1988, p. 43), but it is
considered here that this similarity is superficial. Although the clade including the torpedo rays is predicted
to have originated in the Jurassic (e.g. Shirai 1996), their known fossil record only extends through the
Caenozoic, with the earliest known forms having teeth very different from those of Benthobatis.
Occurrence. Base of Kimmeridge Clay.
Gen. et sp. indet.
Plate 1, figure 12
Material. One partial tooth P. 65679.
Description. The preserved labial face of the crown is relatively triangular and slightly convex with a smoothly curved
basal edge. Much of the height is made up of the main cusp, with at least one small lateral cusplet. A cutting edge is
developed across both preserved cusps.
Remarks. This poorly preserved tooth is of typical hemiscylliid morphology and somewhat resembles the
extant genus Chiloscyllium. Similar teeth have been recorded in the Toarcian (Delsate and Lepage 1990,
fig. 1.4) and Aalenian (Thies 1989, figs 3, 5).
Occurrence. Base of Kimmeridge Clay.
Order HETERODONTIFORMES Berg, 1940
Family HETERODONTIDAE Gray, 1851
Genus PARACESTRACION Koken (in Zittel), 1911
Type species. Cestracion falcifer Wagner, 1857.
Diagnosis based on dental material. Very strongly heterodont. Teeth of juveniles and anterior teeth of
mature individuals have a flat labial surface with smoothly curved basal edge. The triangular central cusp
is flanked by smaller paired lateral cusplets. The uvula is narrow and tapering but well developed. The root
is low and holoaulacorhize, with basal faces narrow and curved. Some lateral and antero-lateral teeth of
juvenile and immature individuals are similar but wider with cusps directed commissurally. Lateral teeth
of mature individuals are ‘molariform’, with a wide and highly ornamented occlusal surface having a well-
developed longitudinal crest.
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 305

Remarks. The genus Paracestracion was originally erected for Paracestracion falcifer, a species known
from a number of complete and partial skeletons from the German Upper Jurassic. This was recognised as
differing from extant species of Heterodontus in several respects (Koken 1911). Characters used for this
initial definition of Paracestracion were subsequently recognised as being unreliable for generic diagnosis
(Schweizer 1964; Maisey 1982). Despite this, P. falcifer differs from both extant Heterodontus species and
the contemporaneous H. zitteli Eastman, 1914 in possession of partly vascularised fin spines and a more
posteriorly positioned first dorsal fin (Maisey 1982). The lack of descriptions of the differences in dentition
between Paracestracion and Heterodontus may have been one of the main reasons for the failure of some
more recent workers to recognise Paracestracion as a separate genus (e.g. Thies 1983; Cappetta 1987).
The dentition of Paracestracion is very similar to that of Heterodontus, with pectinate anterior teeth
similar to those of juvenile Heterodontus. This tooth morphology, however, is retained into adulthood in
Paracestracion, and is not replaced by teeth with an elongate crown and a high hemiaulacorhize root
typical of more mature Heterodontus. Molariform lateral teeth of Paracestracion are very similar to those
of some species of Heterodontus (Maisey 1982), but their presence only in larger individuals (Schweizer
1964) and relative rarity in isolated assemblages suggests that they may develop at a later stage of
ontogeny. The absence of molariform teeth from some assemblages (e.g. Batchelor and Ward 1989) may
suggest that these teeth were never developed within some species of Paracestracion. As anterior teeth of
juvenile Heterodontus are not readily distinguishable from teeth of Paracestracion, it is only in cases
where teeth from non-juvenile individuals are present that generic identification can be carried out with
certainty (this may be evidenced by the presence of a range of tooth sizes and/or the presence of
molariform lateral teeth). The presence of anterior teeth characteristic of adult Heterodontus allow the
genus to be recognised. If only pectinate anterior teeth are present within a population of different sized
teeth, Paracestracion may be identified.
Recognition of a combination of dental characteristics unique to Paracestracion allows several additional
species to be referred to this genus, giving it a stratigraphic range from Toarcian to Tithonian. These are: (1)
Heterodontus sarstedensis Thies, 1983 from the Toarcian of Belgium (Delsate and Lepage 1990) and the
Aalenian of Germany (Thies 1983); (2) an unnamed species from the Bathonian of England (Young 1982,
fig. 2G–H, J–K, M–N); (3) Heterodontus sp. from the Callovian of England (Thies 1983; Martill 1991).
Paracestracion fin spines are known from the Callovian and Kimmeridgian of England (Maisey 1982).
Heterodontis zitteli and H. semirugosus (Plieninger, 1847) are retained in Heterodontus due to skeletal and
dental characteristics respectively, as are all described post-Jurassic heterodontiformes. ‘Heterodontus’
duffini Thies, 1983 teeth bear little resemblance to those of any known heterodontiform and is almost
certainly an orectolobiform.
Paracestracion falcifer (Wagner, 1857)
Plate 2, figures 1–9
1857 Cestracion falcifer Wagner, p. 290.
1964 Heterodontus falcifer (Wagner); Schweizer, p. 69, fig. 3, p. 112, figs 2–4.
1995 Protospinax sp.1; Candoni, p. 38, figs 1–2.
306 P A L A E O N T O L O G Y , V O L U M E 4 5
E X P L A N A T I O N O F P L A T E 2
All specimens from lens between Wyke and Black Head siltstones.
Figs 1–9. Paracestracion falcifer (Wagner, 1857). 1–2, P. 65681, lateral tooth of adult, width 3·5 mm; · 17. 1,
occlusal view. 2, oblique lingual view. 3–5, P. 65682, anterolateral tooth of juvenile, width 1·6 mm; · 26. 3, basal
view. 4, posterior view. 5, labial view. 6–7, P. 65683, anterior tooth of adult, width 2·1 mm; · 26. 6, labial view. 7,
basal view. 8, P. 65684, lateral tooth of juvenile, labial view, width 1·2 mm; · 45. 9, P. 65685, anterior tooth of adult,
labial view, width 2·4 mm; · 25.
Figs 10–14. Synechodus plicatus sp. nov. 10, P. 65691, anterior tooth, labial view, height 3·7 mm; · 12. 11, P. 65687,
symphyseal tooth, labial view, height 1 mm; · 36. 12–14, P. 65686, holotype, lateral tooth, width 3·2 mm; · 19. 12,
posterior view. 13, labial view. 14, lingual view.

P L A T E 2
UNDERWOOD, Paracestracion, Synechodus

Material. 36 anterior and juvenile teeth including P. 65682–65685; two lateral adult teeth including P. 65681.
Description. This species shows extreme ontogenetic and monognathic heterodonty. Adult lateral teeth are elongate in
occlusal view, with the lingual edge being rather convex but the labial face being flat or slightly concave. The occlusal
surface is traversed by a strong longitudinal ridge, which is displaced lingually. Somewhat irregular and sinuous ridges
branch off this on the lingual side, with a finer and more reticulate ornament to the labial side. The crown is uniformly
low with no ornament on the edges, and with the basal edge expanded into a weak uvula on the lingual side. The root is
low and narrower than the crown, with the basal face being slightly curved with the convex side toward the lingual
edge. At least two well-developed foramina are present on the lingual face of the root, but it is unclear whether the root
is holoaulacorhize or hemiaulacorhize due to damage.
Anterior teeth have an oval, bilaterally symmetrical crown with well-developed cusps projecting lingually. In most
teeth these cusps show intense wear, and have been almost completely removed in many specimens. Where present,
the main cusp is triangular and at least as long as wide, usually being flanked by two pairs of lateral cusplets. The inner
pair of cusplets is well developed whilst the outer pair, where present, are very small and project somewhat laterally.
All cusps are rather flattened with well-developed cutting edges. The labial edge of the crown is smoothly curved. The
lingual edge of the crown is narrow with a small central uvula, which is strongly triangular. The edge of the crown is
somewhat flared in some teeth. The root is low, with the basal face being roughly parallel or at a low angle to the labial
surface of the crown. It is shorter than the crown but of similar width, the basal face being relatively parallel sided and
smoothly curved. This is cut by a strong nutritive groove in all teeth which has a large central foramen. Other foramina
are small and largely confined to the lingual face.
Lateral and anterolateral teeth of juvenile and immature individuals are generally similar to anterior teeth. They
differ largely in that the cusps are strongly angled to the posterior making the teeth far less symmetrical. The single
well-preserved lateral tooth of a juvenile has short cusps and a rather concave labial face to the crown. Strongly
elongated cuspate teeth, such as those noted by Schweizer (1967), were not found.
Remarks. The assemblage of teeth demonstrates a very similar range of morphologies to those noted by
Schweizer (1964) in specimens from the Nusplinger plattenkalk. It is very likely that Paracestracion fin
spines from the Kimmeridge Clay of the Weymouth area (Maisey 1982) are conspecific with this species.
The high degree of wear on many of the teeth is typical of anterior teeth of P. falcifer immediately prior to
their being shed (Schweizer 1964).
Occurrence. Immediately below Wyke Siltstone and lens between Wyke and Black Head siltstones.
Genus HETERODONTUS de Blainville, 1816
Type species. Squalus philippsi Schneider, extant.
Heterodontus cf. semirugosus (Plieninger, 1847)
Text-figure 4A–D
1847 Acrodus semirugosus Plieninger, p. 227, fig. 17.
1852 Hemipristis bidens Quenstedt, p. 269, figs 21–22.
1961 Heterodontus semirugosus (Plieninger); Schweizer, p. 110, figs 1–3, 7–8; p. 111, figs 1–3.
1995 Heterodontus sp.; Candoni, p. 38, figs 1–3.
Material. Two imperfect anterior teeth: P. 65711 and 65712.
Description. The crown of the tooth has a rather triangular labial face, with about half of the height being made of the
main cusp. A pair of smaller triangular lateral cusps project slightly laterally. The basal edge of the labial surface is
strongly flared, giving a somewhat constricted shape to the labial part of the crown. A relatively strong lingual uvula is
present. The root is relatively low and overhung by the crown on all sides. There is a strongly V-shaped basal face
enclosing a large basal foramen. A pair of relatively well-developed lateral foramina is also present.
308 P A L A E O N T O L O G Y , V O L U M E 4 5

Remarks. These teeth compare very well to anterior teeth of H. semirugosus figured by Schweizer (1961).
This species is included here for purposes of comparison with P. falcifer and to demonstrate the presence
of a second heterodontiform in the Kimmeridge Clay of Dorset. It is possible that H. zitteli represents a
juvenile specimen of this species, being only known from a single, very juvenile individual (Maisey 1982).
It is likely that a Heterodontus fin spine from the Kimmeridge Clay of the Weymouth area (Maisey 1982)
is conspecific with this species.
Occurrence. Rare at Small Mouth Sands.
Superorder SQUALEA Shirai, 1996
Order SYNECHODONTIFORMES Duffin and Ward, 1993
Family PALAEOSPINACIDAE Regan, 1906
Genus SYNECHODUS Woodward, 1888
Type species. Hybodus dubrisiensis Mackie, 1863 from the Upper Cretaceous of southern England.
Synechodus plicatus sp. nov.
Plate 2, figures 10–14; Plate 3, figures 1–5
1995 Palaeospinax sp.; Candoni, p. 39, figs 1–2.
1995 Synechodus sp.; Candoni, p. 39.
Derivation of name. From the folds on the crown of lateral teeth.
Holotype. P. 65686.
Material. 289 complete and partial teeth from all parts of jaw including P. 65687–65693.
Diagnosis. The dentition is highly heterodont. The crown of anterior teeth is symmetrical and as high as
wide, with the robust main cusp with one or two pairs of very short but robust lateral cusplets. The labial
face is largely unornamented other than some very fine longitudinal folds. The lingual face is
unornamented. Anterolateral teeth have a crown wider than high. The central main cusp is angled to
the posterior. One to three cusplets are present to the posterior of the main cusp. Three to four anterior
cusplets are partially fused to give an irregularly serrated blade. Labial ornament consists of fine
longitudinal folds, straight on the main cusp but more irregular and sinuous on lateral cusplets. Basally,
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 309
TEXT-FIG. 4. A–D, Heterodontus cf. semirugosus (Plieninger, 1847). A–C, P. 65712, Small Mouth Sands, anterior tooth.
A, labial view. B, lateral view. C, lingual view. D, P. 65711, Small Mouth Sands, partial anterior tooth.

these folds divide to form a narrow band of reticulation. Lingual ornament is similar but finer. The thin and
wide crown of posterior teeth has an occlusal ridge and may have the main cusp present as a central striated
cone. Labially and lingually to this is a narrow band of reticulate ornament. The crown very strongly
overhangs the root in all but the most posterior teeth. These are high and thick with a flat basal face in
anterior teeth, becoming narrow and high posteriorly. Very strong, irregularly spaced, vertical folds are
present on the labial face of the root.
Description. This species shows very strong gradient monognathic heterodonty, with the large number of specimens
collected allowing a good approximation of the dentition to be reconstructed. Symphyseal teeth are small with a main
cusp flanked by a pair of well-developed lateral cusplets. Cusps are all ornamented by few strong longitudinal folds,
which branch off a single sinuous transverse fold near the base of the crown. The root is high and rather flared laterally,
with a large foramen between a pair of globular projections of the labial face. Relatively bilaterally symmetrical teeth,
other than from symphyseal files, are rare, which may suggest that they constituted only one or two anterior files. These
teeth are large and, in contrast to all other teeth, very poorly ornamented. The labial face of the crown has a concave
basal edge and rounded lateral edges. The main cusp is conical and robust, somewhat swollen at the base in some teeth.
A weak but continuous cutting edge is present. Lateral cusplets are small, with either two pairs or one pair plus a pair of
incipient cusplets. Ornament is poorly developed, consisting of 2–4 extremely faint longitudinal folds on the sides of
the main cusp. The crown overhangs the root very strongly along its basal and lateral edges. The root is massive and
has a flat basal face. It is strongly pseudopolyaulacorhize, with irregular longitudinal folds on the labial face. The
lingual face is sloping and has very weak crenulations and numerous, irregularly spaced foramina. Anterolateral teeth
are less symmetrical than teeth from the most anterior files. The crown is wider than high, with a central main cusp.
This is conical and angled slightly to the posterior and may be slightly curved lingually. One to three lateral cusplets
are present on the posterior side of the main cusp. These are short and conical, decreasing in size laterally. On the
anterior side of the main cusp, up to four cusplets are present. These are strongly fused to give an irregularly serrated
occlusal surface with a well-developed cutting edge. The crown is ornamented by fine longitudinal folds, which reach
the apex of the cusps. Up to eight such folds are present on the labial face of the main cusp, slightly more on the lingual
face. Similar but rather more irregular folds are present over both faces of the lateral cusplets, being finer on the lingual
face. Towards the base of the crown, irregular bifurcation of the folds creates a narrow band of reticulate ornament.
This reticulation is well-developed on the labial face below the lateral cusplets. It may also be present, but less well
developed, on the lingual face and at the base of the main cusp of some teeth. The root is similar in the more anterior
teeth, but wider and shallower with the crown being angled nearly at right angles to the basal face of the root. The
crown of posterior teeth is wide and shallow. In some posterior teeth, a small central cusp is present, with both faces
ornamented by irregular folds forming a reticulate pattern on the lower part of the face. Where no cusp is present, the
occlusal face is flat other than a well-developed transverse ridge. This is flanked by paired strips of reticulation. The
crown overhangs the root on all sides. The root is high and shallow, especially in commissural teeth.
Remarks. Anterior teeth of Synechodus plicatus sp. nov. are similar to those of S. riegrafi (Thies, 1983), of
which only anterior teeth have been figured, but differ in that teeth of S. riegrafi have higher lateral
cusplets and an ornament of strong longitudinal folds which do not become reticulate at the base. Teeth of
other species of Synechodus lack either the irregularly fused cusplets on anterolateral teeth or the reticulate
ornament at the base of the crown. A lateral tooth figured as Synechodus sp. from the Upper Jurassic of
Germany (Leidner and Thies 1999) and an anterior tooth described as Paraorthacodus sp. from the Upper
Jurassic of France (Candoni 1995) are similar to S. plicatus, but differ in being considerably more
symmetrical and lacking fusion of the anterior cusplets.
310 P A L A E O N T O L O G Y , V O L U M E 4 5
E X P L A N A T I O N O F P L A T E 3
All specimens from lens between Wyke and Black Head.
Figs 1–5. Synechodus plicatus sp. nov. 1, P. 65693, anterolateral tooth, labial view, width 3·4 mm; · 14. 2, P. 65690,
lateral tooth, labial view, width 3·3 mm; · 19. 3, P. 65692, anterolateral tooth, labial view, width 3·2 mm; · 17. 4, P.
65688, commisural tooth, oblique lingual view, width 1·5 mm; · 41. 5, P. 65689, posterior tooth, oblique labial view,
width 3·3 mm; · 18.
Figs 6–12. Protospinax planus sp. nov. 6–8, P. 65694, holotype, anterior tooth, width 1·5 mm; · 36. 6, occlusal view.
7, basal view. 8, lateral view. 9–11, P. 65695, lateral tooth, width 1·7 mm; · 35. 9, occlusal view. 10, basal view. 11,
lateral view. 12, P. 65696, anterior tooth, occlusal view, width 1·9 mm; · 30.

P L A T E 3
UNDERWOOD, Protospinax, Synechodus

Occurrence. Present in almost all samples studied; frequent at Small Mouth Sands.
Superorder HYPNOSQUALEA Carvalho and Maisey, 1996
Family PROTOSPINACIDAE Woodward, 1919
Genus PROTOSPINAX Woodward, 1919
Type species. Protospinax annectans Woodward, 1919 from the Upper Jurassic of southern Germany.
Protospinax planus sp. nov.
Plate 3, figures 6–12
?1990 Protospinax annectans Woodward, 1919; Batchelor and Ward, p. 193, pl. 3, fig. 3.
1995 Squalogaleus sp.; Candoni, p. 38.
?1995 ?Rajiforme incertae familiae; Candoni, p. 38.
Derivation of name. From the flat (as opposed to concave) labial face of the crown.
Holotype. P. 65694.
Material. 32 complete and partial teeth including P. 65695–65696.
Diagnosis. Dentition relatively heterodont, with all teeth being bilaterally symmetrical. The thin crown is
oval in labial view, being wider than high, with a flat or very faintly convex labial face. There is a sharply
angled contact between the labial and lingual face with a poorly developed cusp, which may be flanked by
a pair of incipient lateral cusplets. A narrow but well-defined lingual uvula extends about half way down
the lingual face of the root. The hemiaulacorhize root is high in anterior teeth, less so in lateral files, and
somewhat displaced lingually. The root is almost as wide as the crown, with the basal face of the root being
convex and slightly curved lingually. Centro-lingual and centro-labial foramina are very well developed,
as is a single pair of lingual foramina.
Description. Anterior teeth are as high as wide, with the crown being rather erect, the angle between the labial face of
the crown and the basal face of the root being up to 90 degrees. The labial face of the crown is rather wider than high,
being almost flat with only a slight convexity near the cusp. The cusp is poorly developed, being little more than a
triangular lingual termination of the crown. The labial face of this may be flat or slightly convex, and a single pair of
incipient lateral cusplets is present in some teeth. The lingual face of the crown is rather low and is angled at about 90
degrees from the labial face, the contact being sharp but without a well-developed cutting edge. The base of the crown
is flat other than where it extends basally to form a narrow but strong uvula, and strongly overhangs the root. The root is
wide and relatively narrow, being displaced lingually. The lingual face of the root is concave with a swollen base.
There is a very prominent foramen on the lingual face of the root immediately below the uvula, which connects to an
equally well-developed foramen on the basal or labial face. Either side of the uvula is a large lateral foramen, which
may rarely be replaced by two or three smaller foramina. Small foramina are also present on the lateral ends of the
basal face and on the labial face of the root.
Lateral teeth are generally similar but are far lower in overall profile, with the labial face of the crown forming only
a small angle with the basal face of the shallower root. The crown is considerably wider that high, with the cusp being
little more than an angled lingual edge of the crown. The uvula is well developed but shorter than on anterior teeth,
often with a wear facet at its contact with the crown. The root is lower than in anterior teeth, with a flatter and less
swollen basal face. Foramina appear to be equally well developed in all teeth.
Remarks. The type species of Protospinax, P. annectans Woodward, 1919, is known from several
complete skeletons from the Solnhofen Limestone of Bavaria (Carvalho and Maisey 1996). Teeth have
been figured from two specimens, the adult holotype and a juvenile specimen (regarded as the type
specimen of the genus Squalogaleus by Maisey 1976 and Cappetta 1987). The teeth of the juvenile
specimen have been figured a number of times (Woodward 1919, fig. 3; Maisey 1976, text-fig. 8; Thies
312 P A L A E O N T O L O G Y , V O L U M E 4 5

1983, text-fig. 5; Cappetta 1987, fig. 55B–G), with both lateral and anterior teeth being represented. These
are similar to teeth of Protospinax planus sp. nov., differing largely in being far smaller and having more
strongly separated root lobes, with a nutritive groove being present in at least one tooth (Cappetta 1987, fig.
55F–G). Teeth of the adult specimen (Maisey 1976, text-fig. 2; Cappetta 1987, fig. 62B–F) differ from teeth
of P. planus in possessing a very strongly concave labial face of the crown, rather better developed cusps
which project labially, less well-developed uvula and a nutritive groove separating the root lobes. It is,
therefore, evident that P. planus differs from P. annectans in retaining a flat labial face of the crown
throughout ontogeny, and possesses a more robust root which was not observed to possess a nutritive
groove. It is possible that very small and juvenile teeth, which were not recovered during this study, may,
as in P. annectans, possess a nutritive groove. Teeth from the British Callovian referred to P. annectans by
Thies (1983) appear to be closer to P. planus than P. annectans, but differ from it in having a far better
developed cusp, lower root and mildly concave labial face of the crown in lateral teeth. Teeth from the
British Bajocian and Bathonian (Young 1982, fig. 2E–F, I, L and pers. obs.) are also similar to those of P.
planus sp. nov., but are at present too poorly known for comparison. Protospinax lochensteinensis Thies
1983 from the German Oxfordian and P. sp. from the German Toarcian (Thies, 1989) more closely
resemble P. annectans than P. planus.
Occurrence. All Kimmeridgian samples below the Black Head Siltstone; frequent at Small Mouth Sands.
Family SQUATINIDAE Bonaparte, 1838
Genus SQUATINA Dume
´
ril, 1806
Type species. Squatina squatina Linnaeus, 1758.
Remarks. The genus Squatina is represented by a number of extant species which have very similar
dentitions, and it has been suggested (e.g. Herman 1977) that species cannot readily be differentiated by
tooth morphology. Teeth of Cretaceous–Recent Squatina are indeed very similar, but species can be
distinguished. Well-preserved specimens of Squatina are known from the Upper Jurassic of Germany. The
overall body morphology of these agrees well with extant taxa, but the teeth differ somewhat in detail from
those of modern species (Leidner and Thies 1999). The tooth morphology of early species of Squatina is
very similar to that of some genera of orectolobiforms, and it is therefore often difficult to assign species
between these distantly related groups.
Squatina alifera (Mu¨nster, 1842)
Plate 4, figures 1–2
1842 Thaumas alifer Mu
¨
nster, p. 62, fig. 1.
1843 Thaumas fimbriatus Mu¨nster, p. 53, fig. 4.
1856 Thaumas speciosa Meyer, p. 418.
1859 Squatina (Thaumas) speciosa Meyer; Meyer, p. 4, fig. 2.
1991 Palaeobrachaelurus sp. 2; Landemaine, p. 11, fig. 3j–k.
1995 Palaeobrachaelurus sp.; Candoni, p. 39, figs 1–2.
1999 Squatina alifera Mu
¨
nster; Leidner and Thies, p. 32, fig. 1G; p. 36, fig. 3B–C.
Material. One tooth with damaged cusp, P. 65697; second similar tooth from Small Mouth Sands.
Description. The crown is wider than high and overhangs the root labially. A robust main cusp is flanked by wide and
high lateral blades, each of which has a small cusplet about half way along their length, the entire occlusal edge (where
seen) having a well-developed cutting edge. The basal edge of the lateral blades is rather concave. There is a very well-
developed labial bulge, which is as wide as the main cusp and has a raised labial surface relative to the rest of the
crown, which is flat. The lingual face of the crown is concave, other than where a poorly developed uvula is present as a
thin enameloid covering on a slightly raised area of the lingual face of the root. The hemiaulacorhize root is at least as
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 313

wide as the crown, and is relatively high. The lingual face slopes lingually and has a very well-developed ventral
foramen as well as a number of small lateral foramina. The basal face is relatively flat and distinctly V-shaped. The
labial face of the root is strongly excavated and has very large medio-internal foramen. A large medio-external
foramen is present at the lingual apex of the root.
Remarks. This tooth differs from a specimen removed from an articulated specimen of an adult Squatina
alifera only in being slightly wider (Leidner and Thies 1999), a difference which would be expected within
the low degree of heterodonty shown by extant Squatina species. The general tooth morphology is very
atypical of extant Squatina, the low crown, lateral cusplets and high root all being more typical of
orectolobiform teeth. This is even more marked in the teeth of juvenile S. alifera (=S. speciosa Meyer),
which have well-developed lateral cusplets, no clear labial bulge and no lateral blades (see Leidner and
Thies 1999), making them very similar to teeth of some orectolobiforms and heterodontiforms. The
differences in tooth morphology between S. alifera and extant Squatina suggest that it may be appropriate
to refer S. alifera to a different genus. Referral to another genus is, however, considered beyond the scope
of this study until a re-examination of the skeletal remains of S. alifera has been carried out. There is a
close similarity between the teeth of adult S. alifera and teeth of the presumed orectolobid Palaeo-
brachaelurus Thies, 1983. Although generally very similar to Palaeobrachaelurus bedfordensis Thies,
1983 (including P. alisonae Thies, 1983; Batchelor and Ward 1990), S. alifera teeth may be distinguished
by the combination of small lateral cusplets and well-developed labial bulge.
Occurrence. Immediately below Wyke Siltstone.
Squatina ? frequens sp. nov.
Plate 4, figures 3–13
? 1983 Squatina sp.; Thies p. 108, pl. 11, figs 5–6.
1990 Squatina species A; Batchelor and Ward, p. 188, fig. 1.
1995 ‘Squatina’ sp.; Candoni, p. 39.
1999 Squatinidae gen. et sp. nov.; Leidner and Thies, p. 32, figs 1H–I; p. 37, fig. 3D.
Derivation of name. From the high abundance of this species.
Holotype. P. 65698.
Material. Over 500 teeth, the majority poorly preserved, including P. 65699–65700, P. 65703–65704; also P. 65701
from Small Mouth Sands.
Diagnosis. Teeth roughly cruciform with single robust elongate cusp. The labial profile is symmetrical
except in posterolateral files where the cusp is slightly angled to the posterior. The cusp is flanked by a pair
of lateral blades which are shorter than the cusp in all but the most posterior teeth. Lateral blades are
strongly separated from the upper surface of the root, and frequently have incipient cusplets at their
314 P A L A E O N T O L O G Y , V O L U M E 4 5
E X P L A N A T I O N O F P L A T E 4
All specimens from lens between Wyke and Black Head siltstones unless stated otherwise.
Figs 1–2. Squatina alifera (Mu
¨
nster, 1842), P. 65697, immediately below Wyke Siltstone, lateral tooth, width 2·1 mm;
· 27. 1, labial view. 2, lateral view.
Figs 3–13. Squatina? frequens sp. nov. 3–5, P. 65698, holotype, height 1·6 mm; · 28. 3, labial view. 4, lateral view. 5,
lingual view. 6–8, P. 65699, height 2·1 mm; · 24. 6, labial view. 7, lateral view. 8, lingual view. 9, P. 65703, tooth of
juvenile, labial view, height 1·3 mm; · 45. 10, P. 65700, possible symphyseal tooth, labial view, height 1·3 mm;
· 45. 11, P. 65701, probable commisural tooth, Small Mouth Sands, labial view, width 2·4 mm; · 26. 12, P. 65703,
lateral tooth, labial view, width 2·1 mm; · 29. 13, P. 65704, placoid scale, length 1 mm; · 45.

P L A T E 4
UNDERWOOD, Squatina

extremities. A labial bulge is very well developed, being as wide as the base of the cusp. There is no well-
developed uvula, but enameloid covers the lingual face of the root below the cusp, not reaching the basal
face of the root. The hemiaulacorhize root is high and at least as wide as the crown. The basal face is
strongly V-shaped and slightly flared distally. Median foramina are very prominent, and at least two pairs
of foramina are present on the lingual face of the root.
Description. The range of tooth morphologies recognised suggests that this species had rather weak monognathic
heterodonty. The majority of the teeth recovered have a crown that is higher than wide and are bilaterally symmetrical,
with a minority being wider with a somewhat angled cusp. The cusp is straight and triangular with a rounded cross
section and a weak but continuous cutting edge. This continues onto the lateral blades, which are well developed and
relatively parallel-sided. These often have a pair of incipient cusplets at the ends. A large labial bulge is present
opposite the cusp. The labial bulge is somewhat variable in shape, generally being nearly semicircular and about the
same width as the base of the cusp. The crown overhangs the root, especially along the labial edge and at the tips of the
lateral blades. The root is high and somewhat displaced lingually, and is the same width or wider than the crown. An
elongate apron of enameloid covers a somewhat raised ridge on the lingual face of the root. The basal face is convex in
most teeth, becoming rather flatter toward the lateral extremities of larger and more posterior teeth, where it is
frequently flared. A very large medio-internal foramen is present, with a smaller but well-developed medio-external
foramen at the lingual apex of the root. The lingual face of the root has two pairs of foramina, more being present in
posterior teeth. A single symphyseal? tooth has the lateral blades reduced to rounded projections separated from the
narrow root and a very large triangular labial projection.
Remarks. The teeth of this species are here tentatively referred to Squatina, to which it has previously been
referred (e.g. Batchelor and Ward 1990). In detail, these teeth differ significantly from those of Squatina
squatina (Linnaeus, 1758) and other extant species in a number of respects. These include the possession
of a high root with a strongly excavated labial side, lack of a flat base to the root in most teeth, incipient
cusplets on the lateral blades, lateral blades strongly overhanging the root, lack of a well-developed uvula,
narrow crown in most files and probable presence of specialised symphyseal teeth. Based on tooth
morphology alone, this species closely resembles the Cretaceous orectolobiform Cretorectolobus Case,
1978. Despite this similarity, this species is provisionally referred to Squatina owing to the recognition of
teeth conspecific with S.? frequens sp. nov. from skeletons referred to Squatinidae gen. et sp. nov by
Leidner and Thies (1999). Both of the skeletons studied by Leidner and Thies (1999) are poorly preserved
(Thies, pers. comm. 2000), and it is not impossible that further study may suggest an orectolobid affinity
for these remains. Placoid scales extracted from the same skeletal remains are unlike those of other
Jurassic Squatina specimens (Leidner and Thies 1999), and may further suggest the non-Squatina origin of
the teeth. Similar placoid scales were collected in large numbers during this study, associated with the
teeth of S.? frequens. Although rather distantly related, the extreme convergence in tooth morphology
between Squatina and some orectolobiforms is well known within both extant and fossil taxa (e.g. Herman
et al. 1992).
It is uncertain whether these teeth are conspecific with ‘Squatina’ sp. of Thies (1983), the figured
specimens of which could be accommodated within the morphological extremes of S.? frequens, but could
not be considered typical. Teeth of Squatina acanthoderma Fraas 1854 have not been well figured, but
appear to lack the incipient lateral cusplets of S.? frequens and be more inclined to the posterior.
S. acanthoderma also has very different placoid scales, being of a morphotype not recorded during this
study. Teeth of Cretorectolobus doylei Underwood et al., 1999a are also similar to those of S.? frequens, but
can be recognised in having a far smaller labial bulge and lateral blades more closely attached to the root.
Occurrence. Present in all samples, usually as the commonest selachian species. It is also very common at Small
Mouth Sands.
Order RAJIFORMES Berg, 1940
Family RHINOBATIDAE Mu
¨
ller and Henle, 1838 s.l.
Remarks. It is probable that the Rhinobatidae Mu¨ller and Henle, 1838, sensu Cappetta 1987 constitutes a
paraphyletic group (e.g. McEachran et al. 1996; Shirai 1996), with Spathobatis, Belemnobatis and
316 P A L A E O N T O L O G Y , V O L U M E 4 5

probably Squatirhina forming a clade of stem group batoids (Underwood et al. 1999a). This is separated
from all extant rhinobatids by the possession of a primitive cranial skeleton and two dorsal fin spines (Brito
and Se
´
ret 1996).
Genus SPATHOBATIS Thiolliere, 1854
Type species. Spathobatis bugesiacus Thiolliere, 1854 from the Upper Jurassic of France.
Spathobatis bugesiacus Thiolliere, 1854
Text-figure 5A–I
1854 Spathobatis bugesiacus Thiolliere, p. 7, figs 1–2.
1949 Spathobatis bugesiacus Thiolliere; Saint-Seine, p. 45, fig. 25.
1983 Spathobatis bugesiacus Thiolliere; Thies p. 45, text-fig. 6.
1983 Spathobatis? uppensis Thies, p. 111, fig. 5; p. 113, fig. 1.
1983 Spathobatis? mutterlosei Thies, p. 113, figs 2–4.
1983 Spathobatis? sp. 1; Thies, p. 113, fig. 5; p. 115, figs 1–3.
1983 Spathobatis? sp. 2; Thies, p. 115, figs 4–5.
1987 Spathobatis bugesiacus Thiolliere; Cappetta, p. 139, figs B–D.
1995 Spathobatis uppensis Thies; Candoni, p. 38.
1995 Spathobatis mutterlosei Thies; Candoni, p. 38.
1995 Spathobatis werneri Thies; Candoni, p. 38.
1995 Spathobatis bugesiacus Thiolliere; Cavin et al., p. 265, figs 2–6.
?1995 Asterodermus sp. 1; Thies, p. 472, figs L–O, p. 474, figs A–E (scales).
?1995 Asterodermus sp. 2; Thies, p. 474, figs F–G (scales).
?1995 Asterodermus spec. indet.; Thies, p. 476, figs A–D, G, J–K (scales).
1999 Spathobatis bugesiacus Thiolliere; Leidner and Thies, p. 35, fig. 1E (scales).
Material. 49 complete and partial teeth including P. 65705–65706, P. 65709–65710, also P. 65707 and P. 65708 from
Small Mouth Sands.
Description. The population of teeth recovered during this study suggests that dentition of this species is far more
heterodont than has previously been realised. Heterodonty appears to comprise both strong gradient monognathic
variation and moderate sexual heterodonty, the latter indicated by the presence or absence of a small erect conical cusp,
the presence of a cusp presumably indicative of teeth of males. The variations in crown morphology have been well
documented by Thies (1983), in which teeth of differing position in the jaw were referred to different taxa. Extreme
anterior teeth (S.? uppensis of Thies 1983) are relatively uncommon, and may represent a small number of files, as they
are not recognised by Cavin et al. (1995). The crown is higher than wide, with an angle of 90 degrees or less between
the lingual and labial faces. The uvula is especially well developed and at least as long as the tooth crown. The root is
high and globular, with two well-defined root lobes. Anterolateral teeth (S.? mutterlosei of Thies 1983) have a crown
that is at least as wide as high. The lingual edge of the crown is curved with little sign of a differentiated lingual apron,
whilst the labial edge has a variable sized globular or conical cusp with straight or concave faces lateral to this. A well-
developed edge separates the lingual and labial faces of the crown. The uvula is very well developed and at least as
wide as the cusp. The root is lower than in anterior teeth and is at least as wide as the crown. The basal face is flat and
may be angled laterally. Lateral teeth (S.? sp. 1 and S.? sp. 2 of Thies 1983) are wider than high. The crown is similar to
that of anterolateral teeth, with a clear differentiation between teeth with or without a cusp. The uvula is smaller than in
other teeth, but is still very well developed. The root is low and somewhat displaced labially. The flat-based root lobes
are generally separated by a wide nutritive groove, although this is secondarily closed over in a fairly high proportion
of teeth.
Placoid scales probably referrable to this species are not uncommon. These are variable in form, with most of the
morphotypes recognised by Thies (1995) as Asterodermus spp. being present. The material collected here adds nothing
to the descriptions of Thies (1995). It seems highly likely that the association of these batoid scales with teeth of
Spathobatis bugesiacus at two localities in Germany and in Dorset suggests that they are synonymous.
Remarks. Many of the teeth described here, as in Thies (1983), are inseparable from those extracted from
entire skeletons of Spathobatis bugesiacus known (Cavin et al. 1995, figs 2–6). The degree of heterodonty
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 317

exhibited by S. bugesiacus has not previously been recognised, having been partly concealed by the
taxonomic splitting of the tooth assemblages collected by Thies (1983). There are several reasons why
these species are here considered synonymous. Morphological intermediates between the various ‘species’
are present within the material described here, as in the Kimmeridgian of northern France, where it was
recognised as impractical to separate all but the morphological extremes (Candoni 1995). It would be
highly unlikely that several related species would be present in similar proportions across Europe, but the
318 P A L A E O N T O L O G Y , V O L U M E 4 5
TEXT-FIG. 5. All specimens from lens between Wyke and Black Head siltstones unless stated otherwise. A–I,
Spathobatis bugesiacus Thiolliere, 1854. A–B, P. 65709, lateral tooth of female, width 0.8 mm; · 70. 1, occlusal
view. 2, oblique lateral view. C, P. 65710, lateral tooth of male, oblique lateral view, width 0·6 mm; · 85. D–E, P.
65705, anterior tooth of male, width 0·8 mm; · 55. D, occlusal view. E, lateral view. F–G, P. 65706, extreme anterior
tooth, width 0·5 mm; · 55. F, occlusal view. G, lateral view. H, P. 65707, tooth with open nutritive groove, Small Mouth
Sands, width 0·9 mm; · 62·5. I, P. 65708, tooth with closed nutritive groove, Small Mouth Sands, width 1 mm; · 62·5.

same morphotypes are present in similar proportions in three German localities (Thies 1983), northern
France (in which the lateral teeth are referred to S. werneri Thies; Candoni 1995), and Dorset. Other highly
heterodont ‘rhinobatids’ have recently been recognised in the British Lower Cretaceous (Underwood et al.
1999b; Underwood and Rees in press). Lateral teeth are very similar to teeth of Belemnobatis sismondae
Thiolliere, which co-occurs with S. bugesiacus in France. Teeth of B. sismondae may be separated by the
presence of a more gracile uvula, slightly flared lateral edges of the crown and lower root (Cavin et al.
1995). The status of Asterodermus platypterus Agassiz, 1843 is currently uncertain, but it is likely to be
conspecific with S. bugesiacus. The holotype lacks a head, and cannot be recognised on placoid scale
morphology (Leidner and Thies 1999), but the skeletal structure has not been studied in detail.
A variety of placoid scales has been described as species of Asterodermus by Thies (1995). These were
associated with the teeth he described as species of Spathobatis (Thies 1983) and are very likely to be
synonymous with them and hence with S. bugesiacus. A very similar range of scale morphotypes was
recorded during this study, as well as from articulated skeletons assigned to S. bugesiacus and A.
platypterus (Leidner and Thies 1999).
Occurrence. Present in all samples from the Wyke and Black Head siltstones; also frequent at Small Mouth Sands.
Superorder HOLOCEPHALI Bonaparte, 1832
Order CHIMAERIFORMES Patterson, 1965
Family CHIMAERIDAE Woodward, 1891
Genus ISCHYODUS Egerton, 1843
Type species. Chimaera townsendii Agassiz, in Buckland, 1835 from the Tithonian of England.
Ischyodus sp.
Text-figure 6A–C
Material. One mandibular plate P. 65713.
Description. This small plate, only 13 mm in length, is relatively well preserved, lacking only the mesial extremity and
with some damage along the lingual and symphyseal margins. Faint striations on the basal face of the plate appear to be
taphonomic, caused by the teeth or radula of a scavenging animal. The plate is rather rhombohedral in profile and
strongly occluso-basally flattened. The anterior labial margin is sinuous with a strongly projecting labial edge of the
anterior outer tritor. The posterior labial margin is long and slightly convex. The symphyseal margin is short and
strongly divergent from the posterior labial margin. The posterior labial margin is somewhat curved occlusally, but
lacks a well-developed outer tritor. The labial margin is long and irregularly convex. The anterior outer tritor is
moderately well developed and elongate but low. This is only slightly separated from the median tritor, which is low
and relatively poorly developed. A weakly raised area is present on the lingual side of these tritors. The symphyseal
margin is curved occlusally and no clearly defined tritors are visible, although it is possible that some of the damage in
this region is because of wear of poorly defined tritoral areas. The basal face shows a well-developed descending
lamina, extending from the posterior edges of the symphyseal and labial margins. The labial edge of this is well defined
for much of its length, being least prominent to the posterior of the mesial apex. A faint ridge and groove are present
along the posterior labial margin. The posterior part of the basal surface is clearly vascular, and is somewhat curved
basally towards its lingual extremity.
Remarks. The poorly developed tritors and low degree of wear on this specimen suggests that it represents
the tooth plate of a juvenile individual. Numerous nominal species of chimaeroids have been described
from the European Upper Jurassic, including a number of taxa referred to Ischyodus (at least 12 species
according to Woodward 1891). In many cases, the descriptions and figures of these taxa have been poor,
and it is probable that little allowance has been made for ontogenetic and other intraspecific variation,
which is known to be considerable in some extant chimaeroids (Dean 1906; Didier and Nakaya 1999). The
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 319

common practice of using the form of the tritors as diagnostic features ignores the biological factors which
effect tritoral shape, and hence may lead to spurious taxonomy (Stahl 1999). It is therefore probably
inadvisable to refer small and probably juvenile tooth plates to these nominal taxa without a re-appraisal of
the type and referred material.
Occurrence. Lens between Wyke and Black Head siltstones.
P A L A E O E C O L O G Y
Although superficially rather homogeneous, the Lower Kimmeridge Clay of Dorset contains a range of
discrete faunal assemblages indicating a diversity of palaeoenvironments (e.g. Wignall 1990b). The shelly
clays of the lower Kimmeridge Clay are completely bioturbated and contain a very rich and diverse
invertebrate fauna. The sandy clays at the base of the unit contain abundant large epifaunal suspension
feeders (especially the oysters Deltoideum and Nanogyra, serpulids and the brachiopod Torquirhynchia),
as well as common infaunal bivalves (especially Thracia and Pleuromya), mobile epifaunal taxa (cidarid
echinoids and diverse gastropods) and ammonites. Less sandy clays, such as the shelly lens below the
Wyke Siltstone, typically contain a less diverse epifauna (although still dominated by oysters) and more
diverse infaunal bivalve assemblage. The shelly sandstone lens between the Wyke and Black Head
siltstones also contains a rich and diverse invertebrate fauna. This represents a death assemblage with no
fossils seen to be in life position. Within this lens Deltoideum is very rare, but Nanogyra and serpulids are
common. Small gastropods, infaunal bivalves and fragments of small echinoids are common and diverse.
The base of the lens is heavily bioturbated with common Planolites, Rhizocorallium and ?Diplocraterion.
As well as this typical Kimmeridge Clay assemblage, rare fragments of colonial corals were observed,
although the occurrence of these as abraded fragments suggests that they are probably transported or
reworked. It is therefore evident that the Kimmeridgian elasmobranchs formed part of rich and diverse
palaeocommunities, with a diversity of potential food sources.
320 P A L A E O N T O L O G Y , V O L U M E 4 5
TEXT-FIG. 6. A–C, Ischyodus sp., P. 65713, lens between Wyke and Black Head siltstones, mandibular plate. A, occlusal
view. B, basal view. C, labial view.

The diversity of elasmobranch and other fish remains within the Kimmeridgian of Dorset suggests that
fish with a wide variety of feeding strategies filled a complex suite of niches. It is not, however, readily
possible to quantify the biomass of fish at different trophic positions. This is due to both taphonomic
effects and the differing rates of tooth production of different taxa. There is likely to be considerable time-
averaging within the rock units where vertebrate remains are concentrated, and it also has to be noted that
the differential preservation of teeth within the assemblages may suggest that some material has been
transported from other, nearby, environments. Differential production rates of teeth are likely to have
allowed chimaeroids to be strongly underrepresented in the preserved fauna. An individual chimaeroid
would have produced only six tooth plates and one fin spine during its lifespan, as opposed to the
production and shedding of several hundreds or thousands of teeth during the lifespan of sharks and rays.
Despite these reservations, it is possible to analyse the composition of the fauna in very general terms.
It is evident that there were numerous taxa capable of consuming hard-shelled food items (hetero-
dontiforms, Protospinax, Spathobatis, and probably Ischyodus as well as semionotid and pycnodont
actinopterygians). Of these, the common incidence of high levels of tooth wear in heterodontiforms and
Spathobatis, suggest that these groups were commonly durophagous. These probably fed on benthic
molluscs, echinoderms and crustaceans, as well as possibly on ammonites, all of which are common as
fossils associated with the elasmobranch material. These forms were probably all largely benthic.
?Squatina was probably also benthic like extant Squatina and Orectolobus, its clutching-type dentition
(of Cappetta 1986) suggesting that it most likely represented an ambush predator. It is probable that
Synechodus fed in a similar way, but had a dentition also capable of breaking down some shelled prey
items. Ambush predators were therefore probably well represented within the fauna.
It is likely that Palaeoscyllium fed largely on small prey items, but may also have been something of a
generalist. Similar diets could be expected for some of the rare orectolobiformes and possibly for juvenile
Paracestracion, as well as many of the actinopterygian taxa. The larger hybodonts, with their clutching or
tearing dentitions, were active predators of fish and cephalopods. By comparison with other hybodonts,
however, it is unlikely that the species recorded here were either very large (under 1·5 m long) or fast
swimming. Along with actinopterygian taxa such as members of the Pachycormidae, it is likely that these
hybodonts caught their prey through rapid acceleration rather than straight pursuit. Despite the presence of
these moderate-sized predators, it is certain that the top carnivores would have been marine reptiles such as
pliosaurs, ichthyosaurs and crocodilians, the remains of which are common and diverse within the
Kimmeridge Clay.
C O M P A R I S O N W I T H O T H E R F A U N A S
The elasmobranch faunas of the Kimmeridgian of Dorset appear to be amongst the most diverse known
from the Jurassic. Despite this, they are in many ways similar to associations from other open marine
deposits from the Middle and Upper Jurassic and much of the Lower Cretaceous. These typically comprise
moderate diversity assemblages of small heterodontiforms, orectolobiforms, Protospinax, Synechodus and
‘rhinobatids’; Sphenodus, Squatina, hexanchids, scyliorhinids and larger hybodonts are also frequently
present, as are small to medium-sized chimaeroids. These faunas have been recorded from neritic
mudstones in the Toarcian of Belgium (Delsate and Lepage 1990), Aalenian of Germany (Thies 1983),
Callovian of England (Thies 1983; Martill 1991), Kimmeridgian of France (Candoni 1995) and
Hauterivian of England (Underwood et al. 1999). Faunas observed from inner shelf carbonate settings,
such as the Bathonian of England (Young 1982 and pers. obs.) and Tithonian of France (Candoni 1995)
share many similarities, but these tend to differ in containing far fewer orectolobiforms and lack
palaeospinacids, but have a higher diversity and abundance of small hybodonts. Palaeospinacids and
orectolobiforms are likewise rare within plattenkalks, which may represent environments that were both
shallow and somewhat restricted. Tithonian plattenkalks in Germany contain a diverse elasmobranch
fauna (e.g. Schweizer 1964) within which batoids, heterodontiforms and Squatina are especially well
represented, whereas Kimmeridgian plattenkalks from France (Saint-Seine 1949) contain abundant
batoids almost to the exclusion of other elasmobranchs. Deposits representing conditions of reduced
salinity contain diverse hybodonts and common batoids, as in the Kimmeridgian of Germany (Duffin and
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 321

Thies 1997) and Berriasian of England (Underwood and Rees in press), with batoids being absent in near
freshwater conditions.
Although there has been little work conducted on the palaeoecology of early neoselachians, the close
relationship between elasmobranch faunas and facies suggests that Jurassic and Lower Cretaceous taxa were
strongly environmentally controlled. Palaeospinacids, scyliorhinids and hexanchids appear to have been
largely restricted to deeper water environments where the sea-floor was below storm wave base, whilst
orectolobiforms appear to have been at their most abundant and diverse within these settings. Heterodonti-
forms and Squatina appear to have been most abundant within shallower carbonate shelves, the high
frequency of both within German plattenkalks possibly suggesting a close affinity with the reef habitats that
fringed the lagoon complex in which these rocks were deposited. The almost ubiquitous occurrence of
Protospinax within Jurassic marine sediments possibly suggests that it was a very cosmopolitan taxon.
‘Rhinobatids’ also appear to have been cosmopolitan, with a greater tolerence of restricted conditions than
other neoselachians. Although large hybodonts appear to be present within most marine environments, the
increase in number and diversity of smaller hybodonts (especially Lissodus s.l.) in nearshore and reduced
salinity settings suggests that they dominated these marginal marine environments.
Acknowledgements. I thank David Ward and Adrian Brockenshire for their comments and advice and Kees Veltkamp
for use of the SEM and photographic work. I also thank colleagues at the Department of Earth Sciences at the
University of Liverpool for use of laboratory facilities.
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CHARLIE J. UNDERWOOD
School of Earth Sciences
Birkbeck College
Malet Street
London WC1E 7HX, UK
e-mail c.underwood@bbk.ac.uk
Typescript received 7 December 2000
Revised typescript received 26 March 2001
U N D E R W O O D : J U R A S S I C V E R T E B R A T E S 325