Chondrichthyans from a Cenomanian (Late Cretaceous) bonebed, Saskatchewan, Canada

Authors


Abstract

Abstract:  Acid preparation of samples of a bonebed from the Cenomanian of central Canada yielded several thousand well-preserved chondrichthyan teeth, in addition to numerous other vertebrate remains. Teeth and other remains of one species of chimaeroid, one species of hybodont shark, three species of Ptychodus, 10 species of neoselachian sharks and two species of batoid were recorded. The family Archaeolamnidae fam. nov., genera Meristodonoides gen. nov. and Telodontaspis gen. nov. and species Ptychodus rhombodus sp. nov., Telodontaspis agassizensis gen et sp. nov., Eostriatolamia paucicorrugata sp. nov., Roulletia canadensis sp. nov., Cretorectolobus robustus sp. nov. and Orectoloboides angulatus sp. nov. are described. Status of the genus Palaeoanacorax and the species Cretoxyrhina denticulata, Squalicorax curvatus and ‘Rhinobatosincertus are discussed, and reconstructed dentitions of Archaeolamna and Roulletia presented. The fauna is of low diversity and dominated by active hunters, with many species apparently endemic to the northern Western Interior Seaway.

T he Western Interior Seaway was a broad and relatively shallow body of water that, through the ‘mid’ and Late Cretaceous, stretched across the North American continent from the Boreal Ocean in the North to the Tethys Ocean in the south. Rocks deposited within the seaway are well known for their fossil vertebrates, with chondrichthyans, teleosts, reptiles and birds all being well represented (e.g. Russell 1988, 1993). Despite these rich faunas, study has been very uneven, and the sharks and rays have received relatively little attention. In addition, it has been recognized that there were strong biogeographical controls on vertebrate distribution (Nicholls and Russell 1990), resulting in very different assemblages occurring in rocks for the southern and northern parts of the seaway.

Chondrichthyan faunas from the Cenomanian are relatively well known from Texas (e.g. Welton and Farish 1993; Cappetta and Case 1999), but far less so from the mid and northern parts of the seaway. Abundant shark teeth, mainly lamniforms, have been recorded from a number of sites across the central and northern parts of the USA (e.g. Cicimurri 2001a, b; Shimada et al. 2006), but poor illustrations and conservative taxonomy have sometimes rendered these difficult to interpret. Recorded faunas from further north have typically been from shallow water to marginal facies (Case 2001, Cook et al. 2008). Cenomanian vertebrate faunas from more offshore sites typically occur in bone-rich sandstones (e.g. Cicimurri 2001a) or limestones (e.g. Cicimurri 2001b; Shimada et al. 2006), presumably representing hiatal horizons. Similar sandstones, limestones and mudstones are also present in western Manitoba (McNeil and Caldwell 1981, pers. obs.), whereas true bonebeds, usually with a carbonate cement, occur in otherwise generally noncalcareous-laminated mudstones in eastern Saskatchewan (e.g. Cumbaa and Tokaryk 1999; Schröder-Adams et al. 1999, 2001). These bonebeds (Cumbaa and Tokaryk 1999; Cumbaa et al. 2006) contain a very rich fauna dominated by pelagic predatory vertebrates, in particular lamniform sharks, enchodontid teleosts and hesperornithiform birds.

Geological setting

The Upper Cretaceous succession of the Western Interior Seaway across North America has yielded Cenomanian sharks from a number of sites throughout the region (as summarized by Cook et al. 2008). The Cretaceous rocks in central Canada rest unconformably on Palaeozoic and Precambrian basement rocks and are dominated by mudstones, with coarser clastic material and carbonates both being very limited. On the eastern edge, this succession forms the Manitoba Escarpment, a broken line of hills and uplands running from south-western Manitoba and terminating in the Pasquia Hills of eastern Saskatchewan. The foot of the escarpment is largely obscured beneath sediments deposited along the margins of glacial Lake Agassiz. Exposures are limited, but a number of man-made excavations and natural river cliffs are present. Sandstones and siltstones of Albian age are overlain by a series of mudstone formations ranging in age from Cenomanian to Late Campanian. These mudstones are typically laminated, and benthic organisms are very limited in diversity, with only oysters and inoceramids being abundant. Although vertebrate fossils are present throughout the Upper Cretaceous succession, bone concentrations and bonebeds are only known from the Belle Fourche Member of the Ashville Formation. This unit is Cenomanian in age, with the Cenomanian/Turonian boundary being present within the lower part of the overlying Keld member of the Favel Formation (see Cumbaa et al. 2006). Although concentrations of vertebrate material have been recorded at a number of localities in eastern Saskatchewan and western Manitoba, the bonebed from the exposures on the Bainbridge River in the Pasquia Hills (e.g. Cumbaa et al. 2006) has so far yielded the most abundant vertebrate material (see Text-fig. 1). Material from other sites is currently under study.

Figure TEXT‐FIG. 1..

 Map of the Manitoba Escarpment, modified from Cumbaa et al. (2006). The sections of Late Cretaceous escarpment are: 1, Pasquia Hills; 2, Porcupine Hills; 3, Duck Mountain; 4, Riding Mountain; and 5, Pembina Mountain. The sample site in the Pasquia Hills region is marked with a star.

The main exposure on the Bainbridge River is a river cliff known as Royal Saskatchewan Museum locality number 63E09-0003. Owing to the protected nature of the site, full coordinates of the site are kept with the specimens at the Royal Saskatchewan Museum. The majority of the cliff comprises rocks of the Favel Formation (see Schröder-Adams et al. 1999, fig. 7), with the Belle Fourche Member largely obscured below scree. Small exposures do, however, allow the stratigraphy to be recorded, and about 5 m of carbonate-free laminated mudstones are seen. Within the middle part of this are numerous discontinuous, thin beds and starved ripples of very fine sandstone, many rich in fish scales. Although the bonebed occurs within this interval, it is rarely seen at outcrop. Poor exposures and fallen material show that it comprises a level of very discontinuous lenses within the Ostrea beloiti beds, a stratigraphic unit associated with a widespread marker bentonite, believed to be a northern continuation of the ‘X’ bentonite in the western interior of the United States (Cumbaa and Bryant 2001; McNeil and Caldwell 1981). The only lenses found in situ were just over 2 m below this marker bentonite (Cumbaa and Bryant 2001). Bonebed lenses are up to 0.2 m thick and often have a strongly scoured base and irregularly rippled top. Large mudclasts of bentonite are common within the lenses and sorting of clasts is strongly evident. The bonebed is clast supported, with little or no matrix between the clasts of bones, teeth, coprolites and phosphate nodules, which are held together by calcite cement. Most bioclasts in the bonebed are extremely well preserved. All of the neoselachian teeth have their root preserved (with the exception of those that appear to have been partly digested, and there is very little abrasion). The general lack of roots on hybodont teeth may be the result of resorption. Many fragile bird long bones are complete, and a large proportion of broken bones have longitudinal breaks, suggesting early breakage prior to loss of organic material. A small proportion of larger bones are highly abraded, but this is almost unknown amongst smaller specimens.

The Bainbridge River bonebed is sedimentologically similar to one described from the Carrot River, 100 km to the south-west (see Cumbaa et al. 2006), which has a similar fauna but which is much more restricted (Phillips 2008). Both of these bonebeds lie within the ‘middle’ to Late Cenomanian benthic foraminiferal Verneuilinoides perplexus Zone (McNeil and Caldwell 1981), but radiometric age determinations have yet to be made on the Bainbridge locality. The Carrot River bonebed is capped by a bentonite dated by 40Ar/39Ar at 95.17 Ma (Cumbaa et al. 2006). Faunal and sedimentological characteristics of the bioclastic units present elsewhere along the escarpment have not yet been investigated, although they are thought to be roughly synchronous.

Material and methods

Samples of the Bainbridge River bonebed were collected as loose blocks in the stream bed and banks. As clear size sorting could be seen, the coarser-grained blocks were preferentially collected, as these could be seen to contain more large shark teeth and tetrapod bones. Some blocks were weathered, and vertebrate fossils could be collected from degraded heaps of bone material in the field, but the majority were very well lithified and were collected for later acid digestion.

Bonebed samples were broken down in buffered 5–10% acetic acid, with the undissolved residue removed every few days and washed and dried. Samples were sieved and sorted down to 1-mm mesh size. For this study, about 20 kg of bonebed was dissolved and studied, with a further large collection of specimens used for comparative purposes. A single block of about 5 kg total weight yielded 4432 identifiable shark teeth in the >1-mm mesh size fraction.

Despite the large number of shark teeth within the coarse and medium (>1 mm) sieve fractions, there were very few identifiable remains of chondrichthyans in the fine sieve fraction. Not only do the <1-mm sieve fractions contain large quantities of fragmented teleost material, making sorting for chondrichthyan material very time consuming, but shark and ray teeth are genuinely very rare in these fractions compared to the coarser material. For these reasons, it was not practical to sort more than a representative sample of the fine material, resulting in an underrepresentation of the small-toothed taxa.

Larger specimens were ammonium chloride coated before photography and greater focal depth was obtained by digitally blending images of different focal distances. Very small teeth were imaged by SEM, and therefore, have a somewhat different appearance to optically photographed material and are presented on separate plates. Dentitions were reconstructed by comparison with extant taxa, but variations in the relative shapes of parasymphyseal and intermediate teeth and second and third upper anterior teeth between extant taxa make the relative positions of these teeth in the fossil reconstructions provisional.

Specimens were collected under Saskatchewan Heritage Palaeontological Resource Investigation Permit # 06-03P, and are deposited in the collections of the Royal Saskatchewan Museum, Regina, Saskatchewan, prefix RSM.

Systematic Palaeontology

Remarks.  Descriptive tooth terminology largely follows that of Cappetta (1987).

Class CHONDRICHTHYES Huxley, 1880
Subclass SUBTERBRANCHIALIA Zangerl, 1979
Order CHIMAERIFORMES (Berg, 1940) sensuPatterson, 1965
Family EDAPHODONTIDAE Owen, 1846

Genus EDAPHODON Buckland, 1838

Edaphodon sp.
Plate 1, figures 1–2

Figure EXPLANATION OF PLATE 1.

Figure EXPLANATION OF PLATE 1.


Figs 1–2. Edaphodon sp.; ×5.5; P2989.43, partial palatine plate, 1, occlusal view. 2, basal view.
Figs 3–18. Meristodonoides rajkovichi (Case, 2001); all ×6.5. 3–5, P2989.44, posterolateral tooth. 3, labial view. 4, lingual view. 5, basal view. 6–8, P2989.45, lower anterior tooth. 6, labial view. 7, basal view. 8, lingual view. 9–11, P2989.46, upper posterolateral tooth. 9, labial view. 10, lingual view. 11, basal view. 12–13, P2989.47, upper anterior tooth. 12, labial view. 13, lingual view. 14–15, P2989.48, upper lateral tooth. 14, labial view. 15, lingual view. 16, P2989.49, lower anterior tooth, labial view. 17–18, P2989.50, lower lateral tooth. 17, labial view. 18, lingual view.

Material.  One fragmentary palatine plate (P2989.43). Several other indeterminate chimaeroid plate fragments may also be referable to this taxon.

Description.  The identifiable fragment is from the distal part of the left palatine plate. In occlusal view, the anterior inner tritor occupies over a third of the width of the plate and its entire length, with neither end being preserved. The outer part of the occlusal surface is concave and smooth, with the distal end of the outer tritor being just visible at the posterior end of the specimen. The symphyseal edge is smooth and short. The outer part of the basal face of the plate is smoothly convex, becoming flat or concave in the inner part. There is a well-developed descending lamina which extends for half of the width of the plate and is made up of tissue comprising packed longitudinal tubes.

Remarks.  There is no evidence to suggest that the fragments of chimaeroid present here belong to more than one species, although additional taxa may be present. The overall morphology of the plates and the form of the tritors suggests an edaphodontid affinity, and comparisons with better preserved coeval material by Evgeny Popov suggested that they belonged to Edaphodon. All of the remains seen belong to small tooth plates, probably not exceeding 50 mm long, contrasting to far larger sizes reached by tooth plates of many of the species of Edaphodon.

Subclass ELASMOBRANCHII Bonaparte, 1838
Cohort EUSELACHII Hay, 1902
Order HYBODONTIFORMES Maisey, 1989
Superfamily HYBODONTOIDEA Owen, 1846sensuZangerl, 1981
Family HYBODONTIDAE Owen, 1846
Subfamily HYBODONTINAE Owen, 1846

Genus MERISTODONOIDES gen. nov.

Derivation of name.  From the general resemblance to the teeth assigned to Meristodon by Agassiz (based on indeterminate material), which has commonly been used for the genus named here.

Type species. Hybodus rajkovichiCase, 2001 from the Cenomanian, Late Cretaceous of MN, USA.

Included species.  It is considered here that several species can be included into Meristodonoides gen. nov. These are as follows: Hybodus butleriThurmond, 1971 from the Aptian or Albian of Texas; Hybodus montanensisCase, 1978 from the Campanian of Montana and Wyoming; and Hybodus novojerseyensisCase and Cappetta, 2004 from the Early Maastrichtian of New Jersey. A number of other taxa described on fragmentary material are probably also referrable to this genus.

Diagnosis.  Hybodont shark known largely from teeth, but partial fin spines and cephalic spines from sediments where this genus occurs may be congeneric. There is a low degree of heterodonty, which is mainly represented by changes in the relative size of main cusp and lateral cusplets and strength of ornamentation. Separated from other genera by the following combination of characters: (1) tooth close to symmetrical with single, well-developed cusp being erect or slightly inclined lingually with only slight distal inclination in lateral teeth; (2) main cusp round to slightly labiolingually flattened in cross-section with continuous but very weak cutting edge; (3) lateral cusplets absent, incipient or very small relative to main cusp and well separated from it; where they are present there is a degree of heterodonty, presumably dignathic; (4) ornament of longitudinal striae never coalescing to form labial boss except very weakly in posterior teeth of some species; (5) root very low and somewhat expanded lingually, excavated on basal surface (6) root very strongly vascularized, with row of many small foramina below base of crown on labial face, but vascularization on the basal face of root extremely variable. Fin spines probably tuberculate, lacking strong longitudinal ridges.

Remarks.  Teeth of this genus are separated from Hybodus s.s. Agassiz, 1837 (H. reticulatus Agassiz, 1837 and similar forms) by the presence of a single well-developed cusp, very low root and, for some species, lack of a labial boss. Teeth of EgertonodusMaisey, 1987 have multiple, well-developed cusps but are in other respects similar. Teeth of PlanohybodusRees and Underwood, 2008 have a similar overall shape but differ in being far more compressed, having a far better developed cutting edge and having a root with a basal face that is more strongly excavated labially. Teeth of all other Jurassic and Cretaceous hybodont genera have morphologies very different from Meristodonoides gen. nov.

The subgenus Meristodon Agassiz, 1837 was erected for a collection of isolated tooth crowns from the British Early Cretaceous. The figures suggest that these are indeterminate, but are likely to be a mixture of teeth of Egertonodus and Planohybodus. Despite this, the genus Meristodon has been used to refer to teeth from the Late Cretaceous (e.g. Glickman 1980; Underwood and Ward 2008), as the heterogeneous nature of the type material had not been recognized.

The known range of Meristodonoides gen. nov. is from Aptian or Albian (Thurmond 1971) to Early (e.g. Case and Cappetta 2004) or possibly Late (Case 1979, as Hybodus sp.) Maastrichtian. Most records of Meristodonoides gen. nov. have been from within the Western Interior Seaway, but it is also known from Kazakhstan (D. Ward, pers. comm. 2008) and northern Europe (Biddle 1993, as Hybodus sp.; Underwood and Ward 2008, as Meristodon sp.).

Meristodonoides rajkovichi (Case, 2001)
Plate 1, figures 3–18

  • ?1993 Hybodus sp. Williamson et al., p. 449, fig. 3.1.

  • 1999 Hybodus sp. 1. Cappetta and Case, p. 53, figs 1–2.

  • 1999 Hybodus sp. Cumbaa and Tokaryk, p. 61, fig. 5 (pars, 8 teeth in left 2 columns).

  • 2001 Hybodus rajkovichi Case, pl. 1, fig. 5, pl. 2, figs 1–2.

  • ?2001b Hybodus sp. Cicimurri, p. 185, fig. 5a.

  • 2006 Hybodus sp. Cumbaa et al., p. 146, fig. 4.1.

  • ?2008 Hybodus sp. Cook et al., p. 1189, fig. 4A.

Material.  About 2000 teeth studied including P2989.43–P2989.50. Only 20 of the teeth studied have a root preserved.

Description.  Teeth show weak monognathic and dignathic heterodonty. The crowns of teeth of this species are typically about as wide as high, reaching about 8 mm. The tooth is relatively symmetrical, with the main cusp in the centre of the crown. The main cusp is 1.5–2 times as high as broad at the base and is the only well-developed cusp on the majority of teeth. There are one or two pairs of low to incipient lateral cusplets; where more strongly developed the teeth are presumed to be (by analogy with other hybodonts) from upper anterior positions. The main cusp curves gently lingually and in some teeth has a very gentle inclination towards the posterior. The labial face of the cusp is gently convex, separated from a more strongly convex lingual face by a small but continuous cutting edge. Labial ornament is restricted to the lower quarter to half of the main cusp, where it is represented by 6–12 longitudinal ridges, which become stronger towards the base. In the lateral parts of the crown, these ridges are similar or may be stronger and frequently reach the apex of the cusplets or occlusal cutting edge. Ornament on the lingual face is similar but finer, with the ridges sometimes reaching nearly to the apex of the main cusp. The ornament reaches the crown-root junction on the labial side and close to it on the lingual face. The root is preserved in less than one per cent of the teeth. The root is deeper (labiolingually) higher and wider than the crown. The labial face of the root is very low, and flares somewhat towards the base, where there is a large recess in the basal face of the root on the labial side. A row of many very small foramina are present just below the labial crown-root junction. The root lingual face comprises a narrow and lingually sloping shelf and a vertical face. In addition to a row of many very small foramina just below the labial crown-root junction, larger and more irregularly spaced foramina are present across the root face. The basal root face is flat with a hollowed-out recess. Very small foramina are present across the root basal face, the number and size being very variable between individual teeth. Larger and often rather elongate foramina are restricted to the labial side of the root within the recess. Fragments of fin spines tentatively referred to this taxon have an ornament of regularly spaced, oval, tubercles.

Remarks.  Many of the teeth of this species compare well with type material but a greater degree of heterodonty may be seen than previously recognized. Many of the teeth described here have a finer and longer ornament of fine ridges than the figured type assemblage (Case 2001), but intermediate morphologies are present showing this to be intraspecific variation. The presence of a proportion of teeth with clearly developed lateral cusplets, but in all other respects identical to the type material, suggests that a greater degree of dignathic heterodonty is present within this genus than previously recognized. This species is very similar to Meristodonoides butleri (Thurmond 1971), but teeth have a higher and more slender cusp and appear to have a weaker labial ornament and finer lingual ornament (although it is hard to be sure from the drawings of the type material).

The vast majority of well-preserved, isolated, post-Triassic hybodont teeth lack a root, whereas teeth in associated dentitions from the same deposits typically have well-preserved roots (CJU, pers. obs.). This suggests that the loss of the root is not commonly a result of taphonomic processes but was because of resorption of the root-crown contact during tooth dehiscence.

Order INCERTAE SEDIS
Family PTYCHODONTIDAE Jaekel, 1898

Genus PTYCHODUS Agassiz, 1838

Type species. Ptychodus mammillaris Agassiz, 1839 from the Late Cretaceous of Europe.

Ptychodus rhombodus sp. nov.
Plate 2, figures 1–17; Plate 8, figure 1

Figure EXPLANATION OF PLATE 2.

Figure EXPLANATION OF PLATE 2.


Figs 1–17. Ptychodus rhombodus sp. nov. Figs 1–10 × 4.75; Figs 11–17 × 9. 1–2, P2989.51, holotype, anteriolateral tooth. 1, occlusal view. 2, lateral view. 3–4, P2989.52 lower symphyseal tooth. 3, occlusal view. 4, lateral view. 5–6, P2989.53? lower anterior tooth. 5, occlusal view. 6, lateral view. 7–8, P2989.54 lateral tooth. 7, occlusal view. 8, lateral view. 9–10, P2989.55 posterolateral tooth. 9, occlusal view. 10, lateral view. 11, P2989.56 posterolateral tooth, occlusal view. 12–13, P2989.57 posterolateral tooth. 12, occlusal view. 13, lingual view. 14, P2989.58 posterolateral tooth, occlusal view. 15, P2989.59 upper symphyseal tooth, occlusal view. 16–17, P2989.60 posterolateral tooth. 16, occlusal view. 17, lingual view.Figs 18–21 Ptychodus sp.; all ×4.75. 18–19, P2989.62, lower symphyseal tooth. 18, occlusal view. 19, lateral view. 20–21, P2989.63 posterolateral tooth. 20, occlusal view. 21, lingual view.

Figure EXPLANATION OF PLATE 8.

Figure EXPLANATION OF PLATE 8.


Fig. 1. Ptychodus rhombodus sp. nov.; ×25; P2989.61, posterior tooth, occlusal view.
Fig. 2. Squalicorax curvatus (Williston, 1900); ×25; P2989.166, parasymphyseal tooth, labial view.
Figs 3–5. Palaeoanacorax aff. pawpawensis (Siverson et al., 2007); all ×25. 3, P2989.175, parasymphyseal tooth, labial view. 4–5, P2989.176, parasymphyseal tooth. 4, labial view. 5, lingual view.
Figs 6–18. Orectoloboides angulatus sp. nov.; all ×25. 6–8, P2989.177, posterior tooth. 6, labial view. 7, oblique view. 8, lingual view. 9–12, P2989.178, holotype, anterior tooth. 9, labial view. 10, oblique view. 11, lingual view. 12, occlusal view. 13–15, P2989.179, anterior tooth. 13, oblique view. 14, labial view. 15, oblique lingual view. 16–18, P2989.180, posterior tooth. 16, labial view. 17, oblique view. 18, lingual view.
Figs 19–22. Cretorectolobus robustus sp. nov.; ×12.5; P2989.188, holotype, lateral tooth, 18, labial view. 19, occlusal view. 20, lingual view. 21, oblique view.

  • 1999 Ptychodus sp. Cumbaa and Tokaryk, p. 61, fig. 5 (pars, 4 teeth in third column).

  • 2006 Ptychodus anonymusWilliston 1900; Cumbaa et al., p. 146, fig. 4.3.

Derivation of name.  From strongly rhombic shape of most teeth.

Holotype.  P2989.51 (Pl. 2, figs 1–2).

Additional material.  One hundred and fifty-six teeth studied including P2989.52–P2989.61.

Diagnosis.  Teeth small and low. Strong heterodonty, symphyseal teeth quite square in occlusal view, all other teeth asymmetrical and rhombic to some degree. Dentition with many more files of small, rhombic, compressed lateral teeth than larger and more square anterior teeth. Crown low and outer part of crown flat, with small but conspicuous raised ‘cusp’ towards centre of anterior teeth, inclined to posterior in lateral teeth. Ornament continues across all of occlusal face with no clearly defined marginal area. Ornament of four to 15 subparallel ridges (typically 6–10 in lateral teeth, 8–14 in anterior teeth), rarely bifurcating other than close to edge, breaking up to tubercles at edges and often towards labial margin of larger teeth. Root low and strongly lingually inclined. Foramina below root-crown junction on all sides, especially conspicuous on labial root face.

Description.  Teeth are small for the genus, with the largest being 13 mm wide, and the majority less than 10 mm. They demonstrate a high degree of heterodonty although very few symphyseal teeth are present. All teeth are wider than deep, although this is only slightly so in symphyseal teeth; many of the smaller lateral teeth are approximately twice as wide as deep. In occlusal view, all but symphyseal teeth are strongly rhombohedral in shape, with the lingual edge of the tooth displaced posteriorly. The crown on all teeth is low, with the occlusal face being gently convex but with a low but distinct swollen ‘cusp’ on all but the smallest posterior teeth. In lateral teeth, this is on the posterior side of the tooth. The sides of the crown are smoothly concave on lateral and labial faces but there is a well-developed concave notch on the lingual face. The ornament on the occlusal face is rather variable but intermediate forms are present. The dominant ornament are subparallel ridges running from the anterior to posterior side of the crown. In anterior and anterolateral teeth, there are between 10 and 15 ridges, with fewer present in posterolateral teeth, with as few as four ridges in the most posterior teeth. There are occasional examples of ridges bifurcating, largely restricted to close to the lateral and labial margins of the teeth. Towards the lingual edge of many teeth, the ridges become more curved with the concave side towards the labial face. The ridges reach close to the anterior and posterior edges of the crown, breaking up into small tubercles at the crown edge, especially in larger teeth. There is commonly an area of broken ridges or tubercles towards the labial crown edge. There is no marginal area to the crown, and ornament continues unbroken to the crown edge. The crown overhangs the root on all sides. The root is of similar height and narrower than the crown. The root is strongly inclined lingually in all but symphyseal teeth, and in some lateral teeth the lingual margin of the root extends out beyond the lingual margin of the crown. The lateral faces of the root are all flat, and all have small foramina just below the root-crown junction, although these are especially well developed on the labial face. The basal face of the root is flat and has small and irregularly spaced foramina, sometimes with the addition of one or two larger foramina.

Remarks.  These teeth are highly variable in overall shape but intermediate morphologies demonstrate that they clearly belong to a single taxon. The large proportion of highly compressed, small and asymmetrical lateral teeth has not been previously noted with any Ptychodus species; articulated dentitions of Ptychodus decurrens Agassiz, 1838 (see Woodward 1912) do have several files of compressed lateral teeth, but also possess several files of nearly symmetrical anterior teeth, whilst dentitions of other Ptychodus species have proportionally far fewer reduced lateral teeth. This species shares a lot of characteristics with Ptychodus decurrens Agassiz, 1838 and P. anonymusWilliston, 1900, but can clearly be separated from these.

Teeth of P. decurrens share an almost identical occlusal ornament to P. rhombodus sp. nov., but differ in having a crown that has a far more evenly domed profile, lacking the flat surface with central small cusp seen here, and a larger maximum size. It is also probable that the dental formula was different. Teeth of P. anonymus are also similar, but differ in having a more clearly defined granular margin surrounding the ridged occlusal ornament, and a higher and more clearly defined cusp. Ptychodus janewayiiCope, 1874 was erected on some small and strongly rhombic teeth from the Cenomanian of Kansas, which are considered here to probably represent more than one species. Although it is possible that at least one of the type series is conspecific with the material described here (Williston 1900, fig. 9), the two specimens mentioned in the diagnosis (therefore including, by inference, the holotype) have only four and five folds, respectively, far less than recorded on any similar sized tooth of P. rhombodus sp. nov. As the low lateral and posterior teeth of this taxon are not clearly differentiated from those of P. anonymus, it is possible that P. rhombodus sp. nov. has not been recognized in assemblages where its remains are rare. It is likely that P. rhombodus sp. nov. and P. anonymus are closely related, and it is possible that the probable Middle Cenomanian P. rhombodus sp. nov. is ancestral to the Late Cenomanian to Coniacian (Shimada et al. 2006) P. anonymus.

Ptychodus sp.
Plate 2, figures 18–21

Material.  One lower symphyseal tooth and one posterolateral tooth (P2989.62 and P2989.63).

Description.  The larger tooth is 12 mm wide and has a total height of 10 mm, the smaller tooth is 5 mm wide. The crown of the symphyseal tooth is roughly rectangular in occlusal view, being somewhat expanded on the labial edge and having a prominent indentation on the lingual edge. The majority of the crown is taken up by a roughly conical cusp, which is somewhat wider than high. This is surrounded by a narrow but distinct flat marginal area on the lateral edges but is absent on the labial edge. The posterolateral tooth is rather rhombic in profile, with the posterior edge being ‘stretched out’. A prominent domed cusp occupies the central region of the crown. The crown of both teeth is ornamented by about 10 subparallel ridges, which pass over the cusp, some bifurcating on the cusp flanks. In both teeth, ornament fades out to a smooth outer edge of the crown, although there has been some wear or abrasion of the lateral parts of the larger tooth. The labial side of the crown of the larger tooth is ornamented by small but distinct granulation, which is also present on the small area of vertical cusp face on the lingual side. The crown of both teeth is flared basally and overhangs the root on all sides. The root is shallow, especially so in the posterolateral tooth, and slightly displaced lingually. Foramina of various sizes are present just below the crown-root junction on all sides but are especially prominent on the lingual face. The basal face of the root is slightly concave and has several, irregularly spaced, foramina of different sizes.

Discussion.  Teeth are similar to those of both P. rhombodus sp. nov. and P. anonymus, but appear to differ from both. The symphyseal tooth is larger than any comparative tooth of P. rhombodus sp. nov., and both teeth have a far more conspicuous cusp and a more clearly defined marginal area. It is, however, possible that these represent atypical teeth of a large individual of P. rhombodus sp. nov. The general shape and ornamentation are very similar to that of P. anonymus but differ in the lack of a well-defined granular marginal area.

Ptychodus ex. gr. decurrens Agassiz, 1838
Plate 3, figures 1–6

Figure EXPLANATION OF PLATE 3.

Figure EXPLANATION OF PLATE 3.


Figs 1–6. Ptychodus ex. gr. decurrens Agassiz, 1838; all ×4.5. 1–2, P2989.64, upper symphyseal tooth. 1, occlusal view. 2, lateral view. 3–4, P2989.65, anterior tooth. 3, occlusal view. 4, lateral view. 5–6, P2989.66, lateral tooth. 5, occlusal view. 6, lateral view.
Figs 7–22. Cretoxyrhina denticulata (Glickman, 1957); Figs 9–14 × 2.25; Figs 15–22 × 4.5. 7–8, P2989.67, anterior tooth of subadult. 7, lingual view. 8, labial view. 9–10, P2989.68, ? fourth lower tooth of adult. 9, labial view. 10, lingual view. 11–12, P2989.69, posterolateral tooth of adult. 11, labial view. 12, lingual view. 13–14, P2989.70, lower lateral tooth of subadult. 13, labial view. 14, lingual view. 15–16, P2989.71, parasymphyseal tooth of adult. 15, lingual view. 16, labial view. 17–18, P2989.72, ? upper lateral tooth of juvenile. 17, labial view. 18, lingual view. 19–20, P2989.73, posterolateral tooth. 19, labial view. 20, lingual view. 21–22, P2989.74, ? third upper tooth of neonate. 21, labial view. 22, lingual view.

  • 1839 Ptychodus decurrens Agassiz, p. 154, pl. 25b, figs 1–2, 4, 6–8.

  • 1993 Ptychodus decurrens Agassiz, 1838; Welton and Farish p. 59, figs 1–7.

  • 1999 Ptychodus decurrens Agassiz, 1838; Cappetta and Case p. 55, pl. 2, fig. 9.

  • ?1999 Ptychodus decurrens Agassiz, 1838; Cappetta and Case p. 55, pl. 2, figs 7–8.

  • 2001a Ptychodus decurrens Agassiz, 1838; Cicimurri, p. 41, fig. 6C–D.

  • 2006 Ptychodus decurrens Agassiz, 1838; Shimada et al. p. 7, fig. 6.3–6.4.

  • 2006 Ptychodus decurrens Agassiz, 1838; Cumbaa et al., p. 146, fig. 4.5–4.6.

Material.  Three teeth (P2989.64–P2989.66).

Description.  The largest of the teeth referred to this species is from an anterior position and has a maximum dimension of 12 mm, whilst the other, lateral and symphyseal, teeth are somewhat smaller. Both lateral teeth are somewhat asymmetrical and rhombic in occlusal view, the anterior one having similar width to depth, the other being slightly wider than deep. These lateral teeth have a crown that is gently and evenly domed, without a marginal area, with ornament continuing to the crown margins. The symphyseal tooth is rather ‘arrowhead-shaped’ in occlusal view, with a wide and concave lingual margin. The crown is weakly domed, and the ornament does not reach the crown margins. The crown ornament of the largest tooth comprises about 10 well-developed ridges, which grade from smoothly curved near the crown lingual edge to being folded back on themselves near the labial edge. There is some bifurcation of the ridges, and some breaking up of the ridges close to the crown margins, but generally the ornament continues to the crown edge. The ornament of the other teeth comprises numerous subparallel, fine, ridges cover the lingual two-thirds of the crown, with the lingual part being ornamented with irregularly broken ridges and fine granulations. The crown of the largest tooth is somewhat thicker than that of the others, but all have a similar degree of overhang over the root. The edges of the crown are convex on the labial and lateral edges, but concave on the lingual side, especially so in the symphyseal tooth. The root is relatively low and displaced to the lingual edge. Foramina are present both close to the crown-root junction and on the root basal face, with numerous small foramina and scattered larger ones being present in both places.

Discussion.  These teeth agree well with previous descriptions of the species. The teeth considered to belong to this species have rather different ornament, but all share a similar tooth shape and fall within the morphological range of teeth of Pdecurrens. Although several subspecies of Pdecurrens have been named (e.g. Herman 1977), it has been shown that ornament is very variable amongst teeth from the same stratigraphical interval, and even within the same articulated dentitions (e.g. Woodward 1912). The two teeth with the finer ornament are Pdecurrens var. oweni of Woodward 1912. Despite this variation, it is possible that more than one species or form exists, as teeth from the Turonian/Coniacian boundary (Cappetta and Case 1999) appear to have fewer and stronger ridges on the crown than teeth figured from the Albian to Turonian.

Subcohort NEOSELACHII Compagno, 1977
Order LAMNIFORMES Berg, 1958
Family CRETOXYRHINIDAE Glickman, 1958

Genus CRETOXYRHINA Glickman, 1958

Type species. Oxyrhina mantelli Agassiz, 1843 from the Late Cretaceous of England.

Remarks.  Teeth of Cretoxyrhina mantelli have been recorded as extremely widespread in rocks of Albian to Campanian age (for full synonymy and records of occurrence see Herman 1977; Siverson 1992, 1996; Siverson and Lindgren 2005). Throughout the temporal range of the species, distinct changes in tooth morphology occur, with specimens from older rocks generally being smaller, more gracile and having lateral cusplets in many tooth positions, contrasting with the larger, more robust teeth typically lacking lateral cusplets present in specimens from younger rocks (e.g. Siverson 1996; Siverson and Lindgren 2005). Cretoxyrhina denticulata (Glickman, 1957) was erected for Cenomanian material within which lateral cusplets are present in posterolateral teeth. The diagnosis of C. denticulata was vague, and it has been unclear whether these are a temporal morph of C. mantelli or represent a recognizably different species. Siverson (1996) appears to suggest that the two are synonymous but does not include the type material of C. denticulata in the synonymy of C. mantelli. Reexamination of some of the syntype specimens of C. mantelli (CJU, pers. obs.) suggests that C. denticulata represents a species that can be readily separated from C. mantelli.

Cretoxyrhina denticulata (Glickman, 1957)
Plate 3, figures 7–22

  • 1912 Oxyrhina mantelli Agassiz; Woodward, plate XLIII, figs 11–13.

  • 1957 Isurus denticulatus Glickman, p. 105, figs 1–4, 6–17.

  • ?1993 Cretoxyrhina mantelli (Agassiz); Welton and Farish p. 101, figs 1–12, p. 102, figs 1–2.

  • ?1996 Cretoxyrhina mantelli (Agassiz); Siverson, p. 821, figs 1–18.

  • 2000 Pseudisurus denticulatus (Glickman); Zhelezko, plate II, figs 1–5.

  • ?2001a Cretoxyrhina mantelli (Agassiz); Cicimurri, p. 42, fig. 7.i–k.

  • ?2001b Cretoxyrhina mantelli (Agassiz); Cicimurri, p. 185, fig. 5j.

  • 2006 Cretoxyrhina mantelli (Agassiz); Cumbaa et al., p. 146, fig. 4.13.

  • 2006 Cretoxyrhina mantelli (Agassiz); Shimada et al., p. 15, fig. 10.9–10.10.

  • 2008 ?Cretoxyrhina cf. C. mantelli (Agassiz); Cook et al., p. 1192, fig. 5A.

Material.  Nineteen teeth studied including P2989.67–P2989.74.

Description.  The teeth of this taxon appear to largely represent juveniles, with only three teeth of larger, presumed adult, individuals. The largest tooth, probably from the fourth lower file, is 30 mm in greatest dimension. The teeth show a high degree of monognathic and dignathic heterodonty (see Shimada 1997; Siverson 1996; Siverson and Lindgren 2005 for details), as well as ontogenetic heterodonty; the largest tooth here lacks lateral cusplets which are present in smaller teeth from similar jaw positions. Anterior teeth have a cusp that is higher than the tooth width and is about twice as high as wide. The cusp is rather labiolingually compressed and straight but inclined to the posterior. The cusp lingual face is almost flat, whilst the labial face it smoothly convex. The edges of the cusp flare outwards at the base, and in all but a large adult tooth, have a pair of incipient to very low lateral cusplets. The crown is unornamented other than some faint wrinkles near the base of the crown on the lingual face of some teeth. The base of the crown is straight to faintly arched, and does not overhang the root. The root comprises well-developed root lobes forming an internal angle of about 90–100 degrees. The anterior root lobe is longer than the posterior in all teeth seen. The root lobes are relatively parallel sided and have a smoothly rounded to slightly pointed termination. The root is labiolingually compressed with a very wide and flat linguo-basal face. There is a narrow shelf at the base of the crown on the lingual side but no well-developed protuberance. There is a small foramen at the top of the root linguo-basal face, with other foramina being very small and largely confined to a row below the labial crown-root junction. Lateral teeth have a similar overall design to those of more anterior positions, but are wider and lower. The cusp is strongly inclined to the posterior and may be slightly curved in some teeth. This is flanked by a pair of small but conspicuous lateral cusplets, which are roughly triangular in shape. The root lobes are widely separated and the basal angle is very obtuse.

Discussion.  The larger specimens recorded here are similar to those figured by Welton and Farish (1993), which are all large teeth presumably of adults. Teeth of C. mantelli are recorded from younger rocks (e.g. Shimada 1997; Siverson 1996; Siverson and Lindgren 2005) and differ in having a greater maximum size, and have wider cusps and less well-developed cusplets throughout ontogeny, which are largely absent within adults. This material suggests that teeth from almost all jaw positions of juveniles of C. denticulata had lateral cusplets, which are retained in lateral and posterior teeth of adults. Some specimens from the Late Cenomanian only possess lateral cusplets on posterolateral teeth (e.g. Welton and Farish 1993; Siverson 1996) and are only tentatively referred to this species. Although often uncommon, C. denticulata has been recorded in many Cenomanian sites where open marine facies have yielded extensive chondrichthyan faunas. It is, therefore, likely to have been a globally distributed generalist tolerant of a wide range of local conditions.

Family OTODONTIDAE Glickman, 1964

Genus CRETALAMNA Glickman, 1958

Type species. Otodus appendiculatus Agassiz, 1843 from the Turonian of England.

Remarks.  The genus Cretalamna was suggested by Siverson (1999) to belong within the Otodontidae Glickman, 1964, and the dental formula (Shimada 2007) would seem to support this interpretation. There has been discussion about the spelling of Cretalamna (Cappetta 2006), but it is here considered that the predominance of usage in recent years and relative timing of change in ICZN rules and reassessment of the spelling suggest that the spelling used here is correct.

Cretalamna sp.
Plate 4, figures 1–2

Figure EXPLANATION OF PLATE 4.

Figure EXPLANATION OF PLATE 4.


Figs 1–2. Cretalamna sp.; ×2.25; P2989.75, upper lateral tooth, 1, labial view. 2, lingual view.
Figs 3–23. Eostriatolamia paucicorrugata sp. nov; all ×6.5. 3–5, P2989.76, holotype, upper lateral tooth. 3, anterior view. 4, labial view. 5, lingual view. 6–8, P2989.77, ? first lower lateral tooth. 6, labial view. 7, lingual view. 8, anterior view. 9, P2989.78, upper lateral tooth, labial view. 10, P2989.79, lower lateral tooth, labial view. 11, P2989.80, ? third upper anterior tooth, labial view. 12–13, P2989.81, upper posterolateral tooth. 12, labial view. 13, lingual view. 14–16, P2989.82, ? first upper anterior tooth. 14, labial view. 15, lingual view. 16, posterior view. 17, P2989.83, ? third lower anterior tooth, labial view. 18–19, P2989.84, ? lower parasymphyseal tooth. 18, labial view. 19, lingual view. 20, P2989.85, ? second lower anterior tooth, labial view. 21–23, P2989.86, ? second upper anterior tooth. 21, labial view. 22, anterior view. 23, lingual view.

  • ?1993 Cretolamna woodwardi Herman; Welton and Farish, p. 105, figs 1–3.

  • 2006 Cretolamna appendiculata (Agassiz); Cumbaa et al., p. 146, fig. 4.12.

  • 2006 Cretalamna appendiculata (Agassiz); Shimada et al., p. 15, fig. 10.5–10.8.

Material.  One tooth (P2989.75).

Description.  The single tooth is an upper lateral tooth with a slightly imperfectly developed root. The tooth is slightly wider than high with a slightly distally inclined main cusp being over half the total tooth width. The main cusp is higher than wide and has a gently convex anterior edge and concave posterior edge. This is flanked by a pair of triangular lateral cusplets, each about twice as wide as high. All of the cusps are labiolingually compressed, with a very slightly convex lingual face and moderately convex labial face. There is a strong and continuous cutting edge across all cusps. There is no ornament on any of the crown, the base of which is only slightly arched, so that the cusps are all in a row. Enameloid does not extend down over the root on either side. The root is strongly labiolingually compressed, and root lobes are not clearly differentiated, with just a gentle indentation in the central part of the basal edge of the root. Both labial and linguo-basal faces of the root are flat.

Discussion.  The single tooth recovered in this study, in addition to rare teeth recorded from the Carrot River (Cumbaa et al. 2006) appear to belong to a single species that is conspecific with material figured by Welton and Farish (1993) as Cretolamna woodwardi. These teeth differ markedly from the type material of Dwardius woodwardi, with smaller lateral cusplets in anterior teeth and greater labiolingual compression and a straighter root in lateral teeth. The overall tooth design is far closer to that of Cretalamna appendiculata but differs in possessing a more robust root with a far more rounded profile. The tooth described here is also considerably larger then in coeval C. appendiculata. It is here considered that the species C. appendiculata, as typically used, is in reality a number of distinct and readily definable species, of which this is but one.

Family ODONTASPIDIDAE Müller and Henle, 1839 s.l.

Remarks.  Although the extant species Carcharias taurusRafinesque, 1810, Odontaspis ferox (Risso, 1810) and Odontaspis noronhai (Maul, 1955) are all included into the Odontaspididae by Compagno (2001), there is evidence that the ‘family’ is polyphyletic and should be split into two or even three separate families. The taxa within the Odontaspididae have very different dentitions, and these different dental formulae are readily recognized in the fossil record. In addition, molecular phylogenetic work (Human et al. 2006) suggests that O. ferox belongs in a clade with PseudocarchariasCadenat, 1963 and AlopiasRafinesque, 1810, whereas C. taurus is in a clade with the Lamnidae Müller and Henle, 1838. Although defining new families containing extant taxa is beyond the scope of this paper and would involve considerable anatomical study of modern specimens, it is considered here that the Odontaspididae should not be considered as a natural grouping.

Family ODONTASPIDIDAE Müller and Henle, 1839 s.l., ?Odontaspis ferox group

Genus EOSTRIATOLAMIA Glickman, 1980

Type species. Lamna venustaLeriche, 1929 from the Campanian of France.

Remarks.  The genus Eostriatolamia was erected for Lamna venusta and a number of other Carcharias-like taxa from the Cretaceous, including Odontaspis striatulaDalinkevicius, 1935. The genus was considered to be a junior synonym of Carcharias by Cappetta (1987), who stated that the teeth of L. venusta and O. striatula were similar. It is here considered that L. venusta and O. striatula are congeneric, but do not belong to Carcharias.

Teeth of E. striatula very closely resemble those of Cenocarcharias tenuiplicatusCappetta and Case, 1975, the similarities being recognized by Welton and Farish (1993). Cappetta and Case (1999) suggested that C. tenuiplicatus differs from E. striatula in being smaller, thicker, having a less inclined cusp and having stronger lingual ornament. Despite this, figured specimens of both species show great heterodonty and variation in ornament, with no specimens representing the same probable tooth position being figured from both species. It is here considered that Cenocarcharias should be considered a junior synonym of Eostriatolamia, with E. tenuiplicatus and E. striatula being very closely related or possibly conspecific.

Eostriatolamia paucicorrugata sp. nov.
Plate 4, figures 3–23

  • ?2001b Cenocarcharias tenuiplicatus (Cappetta and Case); Cicimurri, p. 185, fig. 5r.

  • 2006 Cenocarcharias tenuiplicatus (Cappetta and Case); Cumbaa et al., p. 148, fig. 5.2.

Derivation of name.  From weak corrugations on the labial face of the crown.

Holotype.  P2989.76 (Pl. 4, figs 3–5).

Additional material.  One hundred and fifty teeth studied including P2989.77–P2989.86.

Diagnosis.  Heterodonty well developed and probably of Odontaspis ferox type. Teeth small and gracile, typically less than 10 mm high. Root and base of crown quite symmetrical in all teeth, with main cusp distally inclined or curved in presumed upper lateral files. Main cusp higher than wide in all teeth, widening towards the base, especially in lateral teeth. Lingual curvature of cusp present in anterior teeth. One or two pairs of short but robust lateral cusplets present in all teeth, clearly separated from main cusp but joined by broad labial base of crown. Cusplets sharply pointed and higher than wide in anterior teeth but similar width and height in lateral teeth. Lateral edge of outer cusplets overhangs outer edges of root, weakly in anterior teeth, strongly in lateral teeth. Base of crown extends at least half way down labial face of root lobes and does not strongly overhang the root in lateral teeth. A continuous and well-developed cutting edge extends over all cusps. Crown ornament restricted to faint and irregular corrugations at base of labial face and, in some teeth, very faint longitudinal striations on lingual face of cusps. The root is strongly bilobed with a very prominent nutritive groove in all teeth. Root lobes form basal angle of 70–140 degrees. Linguobasal face of root slightly arched and flattened.

Description.  Teeth of this species are relatively small, with the largest anterior teeth being 11 mm high. There is considerable heterodonty that appears to follow the same pattern as in Odontaspis ferox.

All anterior teeth and most lower lateral teeth are nearly symmetrical, whilst the main cusp of upper lateral and some lower posterolateral teeth are inclined to the posterior, even though the base is still centrally situated on the tooth. Anterior teeth have a straight and slender main cusp flanked by a pair of small but clearly differentiated lateral cusplets; a second pair of very small lateral cusplets is present on some teeth. The main cusp is triangular in profile, with smoothly tapering sides, and is considerably more than twice as high as wide. The main cusps of lower anterior teeth are very slightly curved lingually but this curvature is not seen in upper teeth. Lateral cusplets of anterior teeth are longer than wide and are slightly divergent. The cusps are united by a well-developed lower part of the crown, which extends for at least half of the length of the root lobes on the labial side. This basal part of the crown is rather swollen and overhangs the root labially. At the crown-root junction on the lingual face, a well-developed, recessed, neck is present around the base of the main cusp. There is typically an indentation on the labial face of the crown between the basal edge and the base of the lateral cusplets. The labial face of all cusps is gently convex, although this may be flat or slightly concave at the base of the main cusp. This face is separated from the strongly convex lingual face by a small but continuous cutting edge. Ornament is weak on both sides of anterior teeth. Ornamentation of the labial face is present in most, but not all, teeth as irregular and short wrinkles at the base of the cusps, usually concentrated in the area between the main and lateral cusps. On the lingual face ornament is also weak or absent, comprising numerous extremely fine longitudinal ridges on the lower third of the main cusp. Roots of all anterior teeth are strongly ‘V’ shaped, with the angles between the root lobes varying from 70 to 110 degrees, largely depending on jaw position. The root lobes gently taper towards somewhat pointed terminations, and the main difference between anterior and posterior root lobes is the degree of angularity of the lobe termination. The labial face of the root is narrow and at least partly overhung by the crown. The lingual side of the root has a well-developed lingual protuberance in all teeth but this is especially well developed in lower anterior teeth where it is very pronounced. A deep and very well-developed nutritive groove is always present. Lingual faces of the root lobes are somewhat concave and there is a marked, but not sharp, angle between the labial and lingual faces. Lower parasymphyseal teeth are not much smaller than other anterior teeth and similar in overall form to other lower anterior teeth but are considerably more compressed anterior distally. A single very small, fragmentary, tooth is probably from an upper parasymphyseal position.

Lateral teeth are wider and lower than anterior teeth, in many jaw positions being approximately as wide as high. In all teeth, the base of the main cusp comprises about a third of the tooth width, being flanked by a single, or more commonly double, pair of lateral cusplets. In profile, the main cusp of all teeth is somewhat concave towards the base, and the base merges with the inner pair of cusplets. The main cusp is erect in lower teeth but posteriorly inclined in upper teeth and does not show lingual curvature in any tooth position. Lateral cusplets are higher than wide when two pairs are present but similar width and height on teeth possessing only one pair. The outer edge of the cusplets overhangs the root lobes, giving a somewhat ‘spearhead’ profile. All cusps are united to a well-developed labial extension of the crown, which extends at least half way down the labial face of the root and forms a distinct overhang at its base in the centre, but not on the root lobes. The lateral parts of the crown on the labial side of the tooth are swollen, and there is typically a concavity at the base of the lateral cusplets, especially in upper teeth. The labial face of all cusps is weakly convex, and there is a strong and continuous cutting edge separating crown lingual and labial faces. Strong and irregular vertical corrugations are usually present on the labial face of the crown but do not extend onto the cusps. On some teeth from both lower and upper positions, these are restricted to a single ridge below the lateral cusplets or absent altogether. The lingual face of the crown is convex and sometimes ornamented with very fine longitudinal striations on the lower part of the main cusp. A well-developed but narrow neck is present along the lingual crown-root junction. Both anterior and posterior root lobes are similar and have an angle between the root lobes of between 115 and 140 degrees. The root of upper teeth is more compressed labiolingually than of lower teeth, and root lobes are somewhat wider but otherwise they are similar. Root lobes are slightly longer than the lateral extent of the crown, with the labial face of the root being partly covered by the crown. The remainder of the root labial face is shallow and somewhat flared towards the base. On the lingual side of the tooth, there is a narrow but prominent shelf below the base of the cusps. This shelf is separated from the linguo-basal face of the root by a clear and relatively sharp edge. The linguo-basal face of the root is quite flat and somewhat concave. Below the base of the main cusp, the root extends lingually, weakly in upper teeth but more strongly in lower teeth, and a very prominent nutritive groove is present. A tooth of presumed third upper anterior/first intermediate position has a morphology intermediate between that of anterior and lateral teeth but is more inclined to the posterior than either and, if it is from an adult, somewhat smaller.

Remarks.  Teeth of Eostriatolamia paucicorrugata sp. nov. are similar to specimens referred to Eostriatolamia striatula and E. tenuiplicatus, and probably represent a closely related species. Although some specimens of E. striatula lack ornament on the labial or both crown faces (specimens of which Dalinkevicius (1935) only tentatively referred to the species), an ornament of short and strong ridges is usually present at the base of the labial face, and fine striations are typically present on the lingual face of the main cusp of teeth referred to E. striatula and E. tenuiplicatus. In contrast, ornament is very restricted on teeth of E. paucicorrugata sp. nov. In addition, lateral cusplets are more robust in E. paucicorrugata sp. nov. than in other, related, species, and there is a greater tendency for a second pair of lateral cusplets to be present, whilst the base of the labial crown face extends further along the root lobes and does not overhang the root to the same degree. Teeth of E. paucicorrugata sp. nov. also resemble those of E. subulata (Agassiz, 1843), but teeth of E. subulata differ in possessing larger lateral cusplets and a straight labial crown base, which does not extend onto the root lobes. E. paucicorrugata sp. nov. teeth differ from those of ‘OdontaspissaskatchewanensisCase et al. 1990 (which is probably conspecific with Carcharias sp. A. of Welton and Farish 1993 but that very small number of specimens recorded for ‘O.saskatchewanensis prevents detailed comparison) by its larger size, wider lateral cusplets and flared labial base of the crown.

Although general tooth morphology of Eostriatolamia paucicorrugata sp. nov. is very similar to that of Carcharias taurus, the lack of the numerous files of reduced posterior teeth present in C. taurus confirm generic separation (Glickman and Averianov 1998). Despite the lack of sufficient material to reconstruct the dentition of E. paucicorrugata sp. nov., it is tentatively suggested that the dental formula would resemble that of Odontaspis ferox. This is suggested by a moderate-sized tooth resembling that of the third upper anterior/first intermediate position of O. ferox, whilst two different sizes of parasymphyseal teeth have been recognized in E. striatula by Dalinkevicius (1935) and are probably also present in this species.

Eostriatolamia paucicorrugata sp. nov. appears to be a species endemic to the northern part of the Western Interior Seaway, being known only from Canada and possibly North Dakota and Wyoming (Cicimurri 2001b). Further south it is absent but replaced by E. tenuiplicatus, which is present in Texas (Cappetta and Case 1975, 1999; Welton and Farish 1993) and Colorado (Shimada et al. 2006). The limited ranges of these species contrasts with the widespread distribution of E. striatula (e.g. Dalinkevicius 1935; Landemaine 1991; Biddle 1993; Siverson 1997).

Family ODONTASPIDIDAE Müller and Henle, 1839 s.l., Carcharias taurus group

Genus ROULLETIA Vullo et al., 2007

Type species. Roulletia bureauiVullo et al., 2007 from the Cenomanian of France.

Roulletia canadensis sp. nov.
Plate 5, figures 1–24; Text-figure 2A–D

Figure EXPLANATION OF PLATE 5.

Figure EXPLANATION OF PLATE 5.


Figs 1–24. Roulletia canadensis sp. nov.; all ×6. 1–3, P2989.102, first lower anterior tooth. 1, labial view. 2, lingual view. 3, anterior view. 4–6, P2989.89, third upper anterior tooth. 4, labial view. 5, lingual view. 6, anterior view. 7–9, P2989.88, second upper anterior tooth. 7, labial view. 8, lingual view. 9, anterior view. 10, P2989.87, first upper anterior tooth, labial view. 11, P2989.103, second lower anterior tooth, labial view. 12, P2989.95, fifth upper lateral tooth, labial view. 13–14, P2989.90, upper intermediate tooth. 13, labial view. 14, lingual view. 15–17, P2989.104, holotype, third lower lateral tooth. 15, lingual view. 16, labial view. 17, anterior view. 18, P2989.101, lower parasymphyseal tooth, labial view. 19–20, P2989.92, second upper lateral tooth. 19, labial view. 20, lingual view. 21–22, P2989.110, lower posterior tooth. 21, labial view. 22, lingual view. 23–24, P2989.97, upper posterior tooth. 23, labial view. 24, lingual view.

Figure TEXT‐FIG. 2..

 Reconstructed dentition of Roulletia canadensis sp. nov. using adult teeth. Scale bar represents 10 mm. A, Upper dentition in lingual view, specimens (left to right P2989.87–P2989.99). B, Lower dentition in lingual view, specimens (left to right P2989.100–P2989.111). C, Same upper dentition in labial view. D, Same lower dentition in labial view.

  • 1999 Carcharias sp. Cumbaa and Tokaryk, p. 61, fig. 5 (pars; bottom tooth centre right column).

  • 2006 Carcharias amonensis (Cappetta and Case); Cumbaa et al., p. 148, fig. 5.1.

  • 2006 Dallasiella willistoni Cappetta and Case; Cumbaa et al., p. 148, fig. 5.3.

  • 2006 Carcharias amonensis (Cappetta and Case); Shimada et al., p. 12, fig. 9.1–9.2.

Derivation of name.  From abundant specimens being apparently restricted to Canada.

Holotype.  P2989.107 (Pl. 5, figs 15–16), third lower lateral tooth.

Additional material.  About 4500 teeth studied including P2989.87–P2989.106; P2989.108–P2989.111.

Diagnosis.  Dentition of Carcharias type with three differentiated upper and three lower anterior teeth, upper intermediate teeth and lower parasymphyseal teeth. All but first upper and lower teeth somewhat asymmetrical. Ornament lacking on all teeth. Crown rather flared on labial face, overhanging top of root. Cutting edge continuous across main and lateral cusps in all teeth. Anterior teeth with steadily tapering, triangular main cusp and very small to incipient lateral cusplets not reaching base of main cusp. Root of all teeth with clearly defined lobes and well-developed nutritive groove. Root of anterior and first lateral teeth strongly ‘V’ shaped. Root lobes roughly parallel sided with rounded terminations and only slightly flattened basal face. Lateral teeth all have main cusp inclined to posterior, in teeth posterior of second lateral position main cusp strongly curved. One pair of lateral cusplets sometimes with incipient outer pair present but short and triangular. Root lobes in lateral teeth with wide and flat basal face giving ‘swollen’ profile to posterior root lobe.

Description.  The dentition of Roulletia canadensis sp. nov. shows very pronounced monognathic and less pronounced dignathic heterodonty. There is no evidence of sexual or significant ontogenetic heterodonty. Despite the heterodonty, characters common to all teeth, or characters with intermediate morphologies between extremes, allow all of the teeth to be assigned to the same taxon. In all teeth the crown is completely unornamented, and a cutting edge is continuous across the entirety of the main and lateral cusps.

There are three anterior teeth in each side of the upper and lower jaw, although the range of sizes of lower parasymphyseal teeth suggests that the size and possibly even presence of the first lower anterior teeth may be very variable. In all anterior teeth, except for some lower parasymphyseal teeth, the main cusp makes up at least half of the total height of the tooth. The first upper and lower teeth are relatively symmetrical, but in all other anterior teeth, the main cusp is inclined to the posterior or, in the case of the third upper tooth, the cusp is erect but the anterior root lobe is enlarged. The main cusp has a very faint sigmoidal curvature, and in profile appears triangular with a regular taper towards the apex. The labial face is almost flat and separated from the very strongly convex lingual face by a weak but continuous cutting edge. The labial face of the crown extends below the base of the main cusp to between a third and half way down the top of the root lobes. It is somewhat flared at the base and overhangs the root. There is a single pair of small but robust lateral cusplets on the lower teeth, but only very reduced or incipient cusplets on the upper teeth. Cusplets are slightly divergent and never reach as high as the base of the main cusp. All anterior teeth have very clearly separated root lobes, which form an internal angle of 90 degrees or less. The root lobes are roughly parallel sides and are slightly labiolingually compressed. A somewhat flattened linguo-basal face is present, but there is no sharply defined contact between this and the rest of the root. The root lobes of all but the first files of teeth are somewhat asymmetrical, having a more angular apex on the anterior lobe and a rounded one on the posterior lobe. There is a swollen, but not strongly projecting, lingual boss, which is bisected by a prominent but shallow nutritive groove. A single foramen is present within the nutritive groove, other foramina are restricted to the upper interior part of the root lobes and are only seen on a small number of teeth. Lower parasymphyseal teeth are similar in many ways to the rest of the anterior teeth, although about half the maximum size and less symmetrical. They are rather variable in shape, with some being very similar to the first lower anterior tooth, only smaller and more anterior-distally compressed, with others being more irregular in form with shorter cusps and strongly asymmetrical roots. Lateral cusplets may be absent or only present on one side. In all cases, the strong nutritive groove is retained, aiding the recognition of even highly distorted teeth.

Upper intermediate teeth are relatively uncommon within the assemblage, possibly suggesting that only one was present in each jaw, or even that they were not present in all individuals. They are very variable in form, but are small, squat and usually strongly asymmetrical. In most teeth, the main cusp is short and triangular with a single lateral cusplet, often with an incipient cusplet on the posterior side. The root has the same general form as in anterior teeth but is short and swollen, often with only one well-developed root lobe.

The probable first two upper and first lower lateral teeth have a morphology which is intermediate between the anterior and remainder of the lateral teeth. The remainder of the lateral and posterolateral teeth have a morphology that is quite distinct from that of the anterior teeth. Lateral teeth are all strongly asymmetrical with the main cusp strongly inclined or, on the more posterior teeth, curved towards the posterior. Presumed upper teeth are somewhat more compressed than lowers, with a rather more ‘blade-like’ main cusp. In all lateral teeth the apex of the main cusp reaches a point level with the posterior end of the root. The main cusp is of a similar height to the root in all but the posteriormost teeth, where it is somewhat shorter. The base of the main cusp comprises somewhat over half of the total width of the tooth, and in the majority of teeth is flanked by a pair of short and triangular lateral cusplets. In some teeth from both presumed upper and lower positions, incipient or very small additional cusplets may be present, generally but not always on the posterior side of the tooth. In posterolateral teeth, the anterior lateral cusplet is commonly fused to the leading edge of the main cusp to form a serration, or is absent altogether. The labial face of all cusps is only slightly convex, and there is typically a weak concavity at the base of the main cusp. The lingual face of the cusps is more strongly convex than the labial face, but all cusps are still distinctly labiolingually compressed. The cutting edge separating labial and lingual crown faces is well developed and continuous. The base of the crown extends a short distance below the cusps on the labial face, with very minor overhang of the root in the central part. The base of the crown on the lingual face is gently arched over the root and has a narrow but well-defined neck. The root of all lateral and posterolateral teeth is strongly labiolingually compressed with a wide and flat linguo-basal face. The root lobes are relatively short, and the sharp angle between the linguo-basal edges of the root lobes is from 90 to 110 degrees. The root lobes are of similar lengths, with a very well-rounded apex to the posterior lobe and a somewhat more angular apex to the anterior lobe. A pronounced shelf is present at the top of the root on the lingual side of the tooth, and there is a sharp angle between this and the root linguo-basal face. A well-developed nutritive groove extends vertically across the entire root linguo-basal face.

Discussion.  Teeth of Roulletia canadensis sp. nov. are extremely common within the samples studied, and comprise the second most abundant chondrichthyan remains. The reconstructed dentition gives a dental formula very similar to that of Carcharias taurus, although differs from it in lacking the small posterior teeth of C. taurus, and probably in having less strongly compressed lower parasymphyseal teeth. Teeth of R. canadensis sp. nov. are distinctly different from those of C. taurus, with greater degree of heterodonty and more compressed and inclined lateral teeth, further confirming the generic distinction.

Roulletia canadensis sp. nov. has teeth similar to those of R. bureauiVullo et al., 2007 from the Cenomanian of France but differs in a number of respects. Teeth of R. canadensis sp. nov. are more gracile and labiolingually compressed. They have a less robust main cusp which is more blade-like in lateral teeth, have wider lateral cusplets and have a root which, in lateral teeth, is less strongly ‘V’ shaped and have wider and more rounded root lobes. Despite these differences, the similarity in overall tooth shape and heterodonty suggest that these two species are congeneric. A second species that is very similar to R. canadensis sp. nov. is ‘Carcharias’ amonensis (Cappetta and Case, 1975) which is present elsewhere in North America in the Cenomanian (e.g. Welton and Farish 1993; Cappetta and Case 1999). Latero-posterior teeth of ‘C.’ amonensis and R. canadensis sp. nov. are very similar, although teeth of R. canadensis sp. nov. have a more curved main cusp and more rounded root lobes. Teeth from other jaw positions are less similar, with R. canadensis sp. nov. having a less erect main cusp and shorter lateral cusplets in lateral teeth, and very much smaller lateral cusplets and a complete cutting edge in anterior teeth.

Roulletia canadensis sp. nov. appears to have been abundant within the northern part of the Western Interior Seaway, being common at a number of sites in central Canada in addition to the one described here (SC, pers. obs.). It is present, if previously unrecognized, in the mid part of the Seaway (Shimada et al. 2006) where it co-occurs with ‘Carcharias’ amonensis (Shimada et al. 2006, fig 9.3). R. canadensis sp. nov. has not been recorded in Texas (Cappetta and Case 1975, 1999; Welton and Farish 1993) where ‘C. amonensis is common. In France, ‘Carcharias’ amonensis and R. bureaui are both known but do not occur at the same stratigraphical levels. Current records, therefore, suggest that R. canadensis sp. nov. was a cool-water taxon, possibly endemic to the northern WIS.

Family ARCHAEOLAMNIDAE fam. nov.

Derivation of name.  From ArchaeolamnaSiverson, 1992, the genus used to diagnose the family.

Diagnosis.  Family known only from disassociated teeth. Dentitions with well-developed ‘lamniform’ heterodonty with distinct tooth morphologies in different jaw positions. Dentitions comprise three upper anterior and typically three lower anterior teeth. Small and variously ‘stunted’ teeth are present in upper parasymphyseal, lower parasymphyseal and upper intermediate positions. No distinct morphological break between lateral and posterior teeth in upper and lower jaws, and largest teeth of dentition in lateral positions. Teeth of typical lamniform morphology with ‘V’ or ‘U’ shaped root and erect cusp flanked by smaller cusplets. Crown ornament weak, irregular or absent. Lingual neck of crown narrow but well defined. Teeth with serrations or cutting morphology are unknown. Root large and dense, with the only well-developed foramen on apex of lingual bulge or within nutritive groove. Nutritive groove absent, small or shallow. Teeth with anaulacorhize vascularization restricted to large or posterior teeth of taxa where a large foramen is typically present.

Included taxa. Archaeolamna is the genus from which the family is diagnosed. In addition, there are several other genera with similar overall tooth morphology but within which the dental formula is unknown. Archaeolamna is known from Albian to Maastrichtian strata (Siverson 1996). Teeth of CretodusSokolov, 1965 are very similar to those of Archaeolamna, differing largely in their much stronger ornament, probably lesser heterodonty and greater maximum size. Cretodus is known from Cenomanian through Campanian strata (Schwimmer et al. 2002). Teeth of DallasiellaCappetta and Case, 1999 are also very similar to those of Archaeolamna, differing mainly in the greater compression of the roots of lateral teeth, and this may also be a member of the Archaeolamnidae fam. nov. Dallasiella is reported from Cenomanian to Coniacian strata (Cappetta and Case 1999; Cumbaa et al. 2006; Cook et al. 2008). Inferred presence of the same dental formula suggests that Telodontaspis gen. nov. (see below) may also be included into the Archaeolamnidae fam. nov. Teeth of ProtolamnaCappetta, 1980a, included into the Eoptolamnidae by Kriwet et al. (2008), also have a number of similarities to the anterior teeth of Archaeolamna. Despite this, morphology of teeth of other positions, and the presumed dental formula, of known species of the Eoptolamnidae readily differentiate the two families. The known range of the Archaeolamnidae fam. nov. is, therefore, Albian to Maastrichtian and was apparently globally distributed.

Remarks.  The dental formula of Archaeolamna differs from that of all other known Cretaceous and Cenozoic lamniforms in possessing teeth in lower parasymphyseal, upper parasymphyseal and intermediate tooth positions (of Cappetta 1987), associated with three large upper anterior teeth. Within Cretaceous lamniforms, upper parasymphyseal teeth are present within Cretoxyrhina (Siverson 1996; Shimada 1997), Cretalamna (Shimada 2007) and Cardabiodon (Siverson 1999; where the indicated first upper anterior tooth may also represent a parasymphyseal), indicating their presence within the Cretoxyrhinidae Glickman, 1958, Otodontidae Glickman, 1964 and Cardabiodontidae Siverson, 1999, respectively, whilst lower parasymphyseal teeth are either absent in all three taxa, or possibly present only in Cretoxyrhina (Shimada 1997). Intermediate teeth (sensuCappetta 1987, defined as stunted teeth growing on the bar between the upper anterior and lateral hollows) are absent in all three species, with the intermediate teeth of Shimada (1997, 2007) here considered as third upper anterior teeth. All three of these tooth positions are absent in extant Lamnidae Müller and Henle, 1838.

Within the extant Odontaspididae Müller and Henle, 1839 s.l., upper parasymphyseal teeth are present in Odontaspis ferox (Risso, 1810) but absent in O. noronhai (Maul, 1955) and Carcharias taurusRafinesque, 1810. Lower parasymphyseal and intermediate teeth are present in all three species, but in O. ferox the intermediate teeth are especially numerous and preceded by only two files of large upper anterior teeth, in contrast to the three of almost all other lamniforms.

The apparently unique presence of all tooth families within Archaeolamna suggests that the tooth formula is the least derived, with progressive loss of files of small teeth in more derived lamniform families, until in the Lamnidae all of these ‘small’ teeth are lost and the third upper anterior tooth is severely reduced.

Genus ARCHAEOLAMNA Siverson, 1992

Type species. Odontaspis kopingensisDavis, 1890 from the Campanian of Sweden.

Archaeolamna ex. gr. kopingensis (Davis 1890)
Text-figures 3A–D, 4A–R

Figure TEXT‐FIG. 3..

 Reconstructed dentition of Archaeolamna ex. gr. kopingensis (Davis 1890) using large teeth of the robust (?female) morph. Scale bar represents 10 mm. A, Upper dentition in lingual view, specimens (left to right P2989.112–P2989.125). B, Lower dentition in lingual view, specimens (left to right P2989.126–P2989.138). C, Same upper dentition in labial view. D, Same lower dentition in labial view.

Figure TEXT‐FIG. 4..

Archaeolamna ex. gr. kopingensis (Davis 1890) A–K × 6; L–R × 4.5. A, P2989.112, upper parasymphyseal tooth, labial view. B–C, P2989.116, upper intermediate tooth. B, labial view. C, lingual view. D, P2989.113, first upper anterior tooth, labial view. E, P2989.123, upper posterolateral tooth, labial view. F–G, P2989.126, lower parasymphyseal tooth. F, labial view. G, lingual view. H–I, P2989.137, lower posterolateral tooth. 8, labial view. 9, lingual view. J–K, P2989.135, lower lateral tooth. J, labial view. K, lingual view. L–N, P2989.130, first lower lateral tooth. L, labial view. M, anterior view. N, lingual view. O–P, P2989.118, second upper lateral tooth. O, labial view. P, lingual view. Q, P2989.139, third or fourth upper lateral tooth showing strong ornament, labial view. R, P2989.140, gracile morph second or third upper lateral tooth, labial view.

  • 1990 Cretodus sp. Case et al., p. 1090, fig. 7a–f.

  • 1996 Archaeolamna aff. kopingensis (Davis, 1890); Siverson, p. 825, pl. 2, figs 1–6.

  • 1997 Archaeolamna sp. Siverson, p. 462, fig. 4A–H.

  • 1999 Carcharias sp. Cumbaa and Tokaryk, p. 61, fig. 5 (pars; upper 3 teeth centre right column).

  • 2001 Cenocarcharias tenuiplicatus (Cappetta and Case); Case, pl. 2, figs 4, 6.

  • ?2001 ?Carcharias amonensis (Cappetta and Case); Case, pl. 2, fig. 7.

  • 2006 Archaeolamna sp. Cumbaa et al., p. 146, fig. 4.10.

  • 2006 Cretodus semiplicatus (Münster in Agassiz); Cumbaa et al., p. 146, fig. 4.11.

  • 2006 Archaeolamna cf. A. kopingensis (Davis, 1890); Shimada et al. p. 15, fig. 10.1.

  • 2008 Dallasiella willistoni Cappetta and Case; Cook et al., p. 1192, fig. 5B.

  • 2008 Archaeolamna cf. A. kopingensis (Davis, 1890); Cook et al., p. 1192, fig. 5C.

Material.  About 4000 teeth studied including P2989.112–P2989.140.

Description.  The assemblage of teeth of Archaeolamna ex. gr. kopingensis shows very varied morphologies, revealing strong monognathic and weak dignathic heterodonty (see above), as well as some ontogenetic and probable sexual heterodonty. Within the tooth assemblage, most of the teeth are reasonably small, with a small number of larger teeth (as used in the dentition reconstruction) and a very small minority of teeth that are at least 50% larger than average. The very largest teeth differ from others in that there are commonly strong but short and irregular longitudinal folds at the base of the labial face of the crown, especially prominent in teeth from posterolateral positions. Larger teeth of all anterior and anterolateral tooth positions appear to be present in both a robust and a gracile morph. These have the same overall shape but the main cusp and the root lobes of the gracile morph are considerably more slender than in the robust morph. The main cusp of the gracile teeth is also somewhat longer for the width of the tooth than in the robust morph. By analogy with some modern lamniforms and carcharhiniforms, it is probable that the gracile morph represents teeth of adult male individuals, whilst the robust morph represents females and immature individuals.

Anterior teeth have a main cusp that is rather higher than the root and a single pair of slightly divergent lateral cusplets. The main cusp is robust and tapers steadily to a point. In lower anterior teeth and presumed first upper anterior teeth, the main cusp is straight and vertical, becoming inclined in some upper anterior teeth (file two) and curved in others (file three). The lateral profile of the main cusp shows a very slight sigmoidal curvature. In all anterior teeth the lateral cusplets on anterior and posterior sides of the tooth are of similar size, and are rather higher than wide. The crown unites the main and lateral cusplets at the base on the labial side, but not on the lingual face, where a narrow neck is present at the base of each of the cusps. The labial face of the cusps is faintly convex, but commonly flat or slightly concave at the base of the main cusp. The lingual face of all cusps is strongly convex, giving them a rather semicircular cross-section. A well-defined cutting edge is continuous across all cusps. The root is bulky and strongly ‘V’ shaped. The root is somewhat asymmetrical in all anterior teeth, with the asymmetry varying with tooth position. The root lobes form an internal angle of 90 degrees or less, depending on jaw position. Root lobes are oval in cross-section, largely compressed antero-distally, but in the posterior lobe this may be twisted towards the lingual side. The terminations of the root lobes are variable in shape, ranging from smoothly rounded to sharply pointed, but are never strongly flattened. The linguo-basal base of the root is not strongly flattened. There is a rather inflated root lingual boss, and in the centre of this is either a single well-developed foramen or a cluster of up to four small foramina. In a small proportion of smaller teeth, the main foramen is within a short but deep groove.

Lower parasymphyseal teeth are very variable but are essentially modified anterior teeth. There appears to be a morphological continuum between first lower anterior teeth and highly modified and stunted parasymphyseal teeth. It is, therefore, likely that the dentition at the front of the lower jaw is less clearly defined than in other lamniforms. The crown of lower parasymphyseal teeth differs from that of other anterior teeth largely in being smaller relative to the root and less symmetrical, with lateral cusplets often being better formed on one side of the tooth than the other, or even absent on one or both sides. The root is antero-distally compressed with a very well-developed lingual boss. Root lobes are short and rarely of close to equal length; in many of the smaller teeth, only a single root lobe is fully developed.

Presumed upper parasymphyseal teeth vary in shape but the majority are relatively symmetrical; other teeth are of similar overall morphology but are distorted and show greater asymmetry. These are less abundant than lower parasymphyseal and upper intermediate teeth and may not have been present in all individuals: there is considerable variation in the presence of these small teeth between individuals of many extant lamniforms (CJU, pers. obs.). The main cusp is robust and rather triangular, although in some of the more asymmetrical teeth, the basal part may be parallel sided. Lateral cusplets are short, triangular, robust and slightly divergent. The shape of the root is rather variable, probably related to whether there were one or more teeth within this jaw position. In the more symmetrical teeth, the root is clearly ‘V’ shaped and relatively robust. The root lobes show very little tapering and have an internal angle of about 80 degrees. There is a swollen lingual region but not as enlarged as in most anterior teeth, and the root lobes are oval in cross-section without a well-defined linguo-basal face of the root. In the remainder of the teeth from this proposed position, the root is more compressed antero-posteriorly, creating a larger lingual bulge. The root lobes are short and not often well defined, comprising considerably less than half of the height of the root.

Upper intermediate teeth are common within the assemblage, and it is, therefore, likely that several files of these were present in the jaw. They are symmetrical and have an erect and triangular main cusp flanked by a pair of slightly divergent cusplets. In respects other than size, the crown of these teeth resembles that of lower anterior teeth. The root is strongly ‘V’ shaped and has an internal angle of 90 degrees or less. The root comprises about half of the height of the tooth. The root is variably compressed labiolingually. In some teeth, the root lobes are oval in cross-section with a slightly flattened linguo-basal root base, whereas in other teeth the linguo-basal face of the root is very flattened, even including the region directly below the main cusp. This flattening extends to the root lobes, which are about twice as wide as they are thick. The lingual foramen is present but very small. In addition, there are a very small number of probable upper intermediate teeth that are small and squat. A triangular main cusp is compressed labiolingually and flanked by a pair of lateral cusplets that are similar in shape to those of lower lateral teeth. The lingual face of the crown is wide at the base and is either smooth or ornamented with irregular wrinkles similar to those seen in other teeth. The lingual face of the crown is smooth other than a very well-developed neck.

Upper lateral and posterior teeth all have a similar morphology, varying largely in their size and the height of the cusps. The first upper lateral tooth has a morphology somewhat intermediate between that of the anterior teeth and the remaining lateral teeth. The main cusp is robust and has a smooth curve along both anterior and posterior edge. In all but in the smallest posterior teeth, the main cusp is of similar height to the root. The axis of the main cusp forms an angle of about 60 degrees with the base of the tooth. There is a single pair of robust lateral cusplets of similar size to each other which are slightly higher than wide. These are slightly divergent, but in more posterolateral teeth, the posterior lateral cusplet is often more erected than the main cusp. In the most posterior teeth, the anterior cusplet may be reduced or incipient. The labial face of the crown is smooth and slightly convex, although on some very large teeth and some posterolateral teeth, small vertical wrinkles may be present just above the crown-root junction. The three cusps are united by a narrow basal strip of enameloid on the labial side of the tooth, but not on the lingual side. There, a very prominent neck is present at the base of each of the cusps. The lingual face of the cusps is smooth and strongly convex. There is a well-developed cutting edge across all of the cusps. The root of upper lateral teeth is bulky and quite symmetrical, and the rather stubby root lobes form an internal angle of 90–100 degrees. The outer edge of the anterior root lobe continues from the edge of the main cusp, with a rounded termination. The labial face of the root slopes gently away from the base of the crown, and there is no labial crown overhang. The linguo-basal face of the root is slightly flattened, with no clear edge to the face. The lingual boss is large and rounded, with one or sometimes two or three foramina at the apex. In some smaller teeth, a very short but deep groove is present. Some small foramina are seen on the upper parts of the root labial face, but are rarely conspicuous.

Lower lateral teeth are very close to symmetrical, with the exception of the probable first lower tooth, which is very similar in shape to the third anterior tooth, and the smaller posterolateral teeth. The main cusp is straight and quite short, with slightly concave outer edges. There is a single pair of relatively large lateral cusplets, that are higher than wide. The base of the lateral cusplets is in line with the base of the main cusp, as opposed to being some way down the outer edge of the root lobes as in teeth from other positions in the jaw. The outer edge of the cusplets overhangs the root slightly, and in some posterolateral teeth this projection develops into an additional incipient cusplet. The labial face of the crown is very slightly convex to almost flat, and has no ornament in the vast majority of teeth. The basal edge of the enameloid on the labial side is gently arched, as opposed to the strong curvature on other teeth. The lingual face of the cusps is smooth and strongly convex, with a well-developed neck at the base of each of the cusps. In posterior teeth, the main cusp is strongly inclined as in the upper teeth, and upper and lower teeth can only be differentiated by the shape of the root. The root of lower lateral teeth is far more ‘square’ than on teeth from other positions; viewed lingually, the top of the root is only slightly arched upwards, and the edges of the root lobes are almost vertical below the outer edges of the lateral cusplets, giving a very sharp angle between these edges. The inner edges of the root lobes form a smooth semicircle in most teeth, becoming more angular in posterior teeth. The root lobes themselves have rounded terminations and are somewhat flattened labiolingually. The labial face of the root smoothly curves away from the crown, with a slight recess below the base of the main cusp. The linguo-basal face of the root is large, making up almost all of the root that can be seen in lingual view, and relatively flat. There is a distinct but not sharply angled edge to this face. The lingual boss projects slightly, giving a narrow horizontal shelf below the cusps. There are one or more foramina at the apex of the lingual boss, and in some smaller teeth these are opened out to form a short but distinct groove. Small foramina are present towards upper part of the labial face of the root, but are small and irregularly distributed.

Discussion. Archaeolamna is known from the Albian to Maastrichtian and appears to have had a virtually global distribution (see Siverson 1996). Of these occurrences, the majority of records relate to Archaeolamna kopingensis (Davis, 1890), although stratigraphical variations suggest that this may represent a group of closely related taxa rather than a single species. In addition to A. kopingensis s.l., A. haigiSiverson, 1996 from the Cenomanian of Australia and A. kopingensis judithensisSiverson, 1992 from the Campanian of the USA (the latter probably deserving of specific rank) are known.

Despite the very high degrees of heterodonty present, it is possible to make general comparisons between the Archaeolamna kopingensis s.l. specimens described here and from other populations. Albian specimens from Europe (Biddle 1993) are typically rather gracile and possess a poorly formed nutritive groove in most or all teeth. Albian specimens from Australia (Siverson 1997) are similar, but the nutritive groove is restricted to smaller teeth. Archaeolamna kopingensis s.l. specimens from the Cenomanian of Australia (Siverson 1996) and probably France (Vullo et al. 2007), as well as younger occurrences, lack a nutritive groove and possess weak folds on the labial face of the larger teeth. The specimens described here are therefore most similar to those from the Australian Albian, differing only in the possession of weak ornament on the labial face of a small number of the very largest and most posterior teeth. Although there are slight differences between different populations of A. kopingensis, it has not been possibly to produce a reliable set of criteria for separating species within what almost certainly represents a complex of morphologically similar taxa.

Within the ‘mid’ Cretaceous, A. kopingensis s.l. is widespread but not global in occurrence. It is common at this site and elsewhere in the Cenomanian of central Canada (SC, pers. obs.) as well as in Colorado (Shimada et al. 2006). It is also present in western Europe (e.g. Biddle 1993; Vullo et al. 2007; CJU, pers. obs.), Russia (CJU, pers. obs. of specimens mislabelled as other species) and Australia (Siverson 1996, 1997). Despite this, it has not been recorded in Texas (e.g. Welton and Farish 1993; Cappetta and Case 1999) or elsewhere in areas associated with Tethys. It, therefore, appears to have been a temperate water inhabitant, present in both Northern and Southern Hemispheres.

Family ?ARCHAEOLAMNIDAE fam. nov.

Genus TELODONTASPIS gen. nov.

Type species. Telodontaspis agassizensis sp. nov.

Derivation of name.  From the spear-like tooth morphology and an Odontaspis-like overall tooth shape.

Diagnosis.  Strong monognathic and dignathic heterodont dentition with anterior teeth up to 12 mm high. Several files of upper and lower parasymphyseal teeth and upper intermediate teeth present. Cusp unornamented, slender and straight, at least 3 times as high as wide, inclined to posterior in lateral teeth and faintly labiolingually sigmoidal in anterior teeth. Single pair of small, triangular, lateral cusplets present in upper lateral teeth, absent in all other teeth. Base of crown with prominent neck on lingual side, and extends along upper third to half of root lobe on labial side. Cutting edge continuous in lateral teeth but not reaching base of crown on anterior teeth. Crown does not overhang root. Root with two clearly defined lobes, of roughly equal size in lower teeth, but with anterior lobe longer than posterior in upper teeth. Lingual face of root with poorly developed lingual protuberance, below which root lobes are either labiolingually compressed with a flat linguo-basal root face in upper lateral teeth, or somewhat expanded lingually with no clearly defined linguo-basal root face. There is a well-developed round to slightly elongate foramen at the apex of the lingual protuberance, with very small foramina spread across the root surface.

Remarks.  The relatively small number of teeth assigned to the single known species of this genus, and the high degree of heterodonty, make reconstruction of the dentition less certain than with some other taxa present in this assemblage. This is made more difficult by the presence of different proportions of teeth in the fossil assemblage than would be expected in the jaw of a living individual, probably because of a combination of differential shedding rates, a range of ontogenetic stages being present and likelihood of random bias in a small sample size. The teeth collected comprise a relatively large number of teeth assigned to parasymphyseal files, and relatively few teeth considered to be lower lateral positions. It is possible that more material would require a different reconstruction of the dentition to be developed. Despite this, it is evident that the overall dental formula is similar to that of Archaeolamna, with three upper anterior tooth positions, upper and lower parasymphyseal teeth, and upper intermediate teeth all being present. In addition, there appears to be a morphological gradation from lower parasymphyseal to lower anterior teeth, as seen in Archaeolamna. Despite this, the number of other lower and upper parasymphyseal teeth suggest that multiple files of these were present in life, a character present in lower jaws of Odontaspis noronhai but not present in the upper jaw of other known lamniforms. The overall tooth shape is not unlike that of Cretoxyrhina mantelli (Agassiz, 1843), but Telodontaspis differs in possessing lower parasymphyseal and upper intermediate teeth and a more strongly developed heterodonty within the upper jaw. Teeth of T. agassizensis sp. nov. are similar in overall morphology to teeth of neonate individuals of Cretoxyrhina mantelli, and have previously been mistaken for that species. Despite this, teeth of T. agassizensis sp. nov. differ in the range of tooth morphologies present within the dentition, most of which clearly do not fit in with the ontogenetic trend of C. mantelli. Teeth are similar to those of Priscusurus adruptodontusKriwet, 2006, although this genus and species was based on a very small sample of material, and so remains poorly defined. Teeth of T. agassizensis sp. nov. differ from those of P. adruptodontus in having a more slender main cusp and, in upper lateral teeth, small lateral cusplets.

Telodontaspis agassizensis sp. nov.
Plate 6, figures 1–27

Figure EXPLANATION OF PLATE 6.

Figure EXPLANATION OF PLATE 6.


Figs 1–27. Telodontaspis agassizensis sp. nov.; all ×4.5. 1–2, P2989.141, ? lower parasymphyseal tooth. 1, labial view. 2, lingual view. 3–5, P2989.142, ? first upper anterior tooth. 3, labial view. 4, anterior view. 5, lingual view. 6–8, P2989.143, ? first upper lateral tooth. 6, labial view. 7, anterior view. 8, lingual view. 9–11, P2989.144, holotype, ? third upper anterior tooth. 9, anterior view. 10, labial view. 11, lingual view. 12–13, P2989.145, ? upper parasymphyseal tooth. 12, labial view. 13, lingual view. 14–15, P2989.146, ? upper intermediate tooth. 14, labial view. 15, lingual view. 16–17, P2989.147, ? upper lateral tooth. 16, lingual view. 17, labial view. 18–20, P2989.148, ? lower parasymphyseal tooth. 18, labial view. 19, anterior view. 20, lingual view. 21–22, P2989.149, ? lower posterior tooth. 21, labial view. 22, lingual view. 23–24, P2989.150, ? second lower anterior tooth. 23, labial view. 24, lingual view. 25–26, P2989.151, ? third upper anterior tooth of juvenile. 25, labial view. 26, lingual view. 27, P2989.152, ? incomplete first lower anterior tooth, labial view.

  • 2006 Cretoxyrhina mantelli (Agassiz)(?); Shimada et al., p. 15, fig. 10.11–10.12.

Derivation of name.  From the locality of the type material being close to the shoreline of glacial Palaeolake Agassiz.

Holotype.  P2989.144 (Pl. 6, figs 9–11).

Additional material.  Forty-four teeth studied including P2989.141–P2989.143; P2989.145–P2989.152.

Diagnosis.  As for genus.

Description.  The teeth of this species are very varied in shape but occur in a number of discrete morphologies relating to positions within the jaw. The relatively small number of teeth prevents the construction of a full dentition, and as a result, tooth positions are partly inferred by comparison with other taxa.

There are two different morphologies of parasymphyseal teeth (Pl. 6, figs 12–13, 18–20), with the commoner, often more asymmetrical, teeth being considered here to come from the upper dentition. These presumed upper parasymphyseal teeth have a straight cusp that is up to half the total height of the tooth. The cusp is straight and slender and, in labial view, tapers steadily towards the apex. It is unornamented in all teeth. There is a very slight lingual curvature in some teeth. The labial face of the cusp is gently convex, separated from the strongly convex lingual face by a narrow cutting edge, which is continuous in some teeth, but only present on the upper half of either the anterior or posterior edge of the cusp on others. There is a well-developed lingual neck at the base of the cusp. The basal edge of the crown on the labial side of the tooth is extended along the root lobes, extending further along the anterior than posterior lobe. The crown basal edge is flat and does not noticeably overhang the root. On the majority of teeth, the cutting edge does not extend along this basal extension of the crown. A small proportion of teeth have an incipient cusplet on the mesial side of the crown. There are two distinct root lobes, the posterior one being about half the length of the anterior in the more asymmetrical teeth. The anterior root lobe has a rounded apex, whilst that of the posterior is usually more pointed. The labial face of both root lobes is slightly concave and merges with the base of the crown, There is a narrow shelf below the base of the crown on the lingual side, terminating in a pointed protuberance with a well-developed foramen at the apex. Below this, the root is strongly labiolingually compressed and the linguo-basal root face is flat to slightly concave. Small foramina are present over the entire root surface.

Teeth referred to lower parasymphyseal positions are rather different. The cusp is slender and is curved lingually and slightly twisted to the posterior. The cutting edge is continuous on the anterior edge, but does not reach the base on the posterior side of most teeth. There is a pair of incipient cusplets at the base of the cusp. The base of the crown is straight on both faces, with a well-developed lingual neck. The labial face of the crown does not overhang the root. The root is relatively bulky, with two root lobes that form an angle of up to 90 degrees. Both root lobes are tapered and have variable rounded terminations. The root lobes are not compressed in either orientation, and the linguo-basal root face is convex. The root is swollen below the lingual base of the crown and has a somewhat slit-like foramina at the apex. Small foramina are present over the remainder of the root surface. Some teeth have a morphology intermediate between this and presumed lower anterior teeth, differing from the latter by being smaller and having longer root lobes.

All of the anterior teeth have an elongate and slender cusp that is higher than the root, and lateral cusplets are absent, although an incipient distal cusplet is present on the presumed third upper tooth. The cusp is weakly sigmoidal in all teeth, but in labial view, is either straight or, in the probable first upper teeth, very gently curved. It is inclined to the posterior in lower and first upper anterior teeth, but inclined to the posterior in the other upper anteriors. In the presumed first and second lower teeth, and to a lesser extent other anterior teeth, the labial face of the cusp narrows towards the base, with the cutting edges moving onto the crown labial surface. At the base of the crown is a well-developed neck in the lingual side, whilst on the labial side the crown enameloid extends for about a third of the length of the upper edge of the root lobes, the crown merging with the root labial face without any overhang. There is a continuous cutting edge which does not reach the crown base in any teeth. The root is robust in all anterior teeth, but more gracile and labiolingually compressed in the second and third upper teeth. The root of lower anterior teeth is relatively expanded lingually, resulting in a well-developed lingual protuberance. This has a well-developed foramen at the apex. In some lower anterior teeth, the root is incompletely developed, but the root lobes are seen to be very short and stubby, considerably less than half the total height of the root and both are of similar size and shape with a rounded root lobe apex. In the third lower teeth, the root lobes are somewhat longer and asymmetrical, with a more pointed anterior root lobe apex and more rounded posterior apex. There is a somewhat flattened area on the linguo-basal face of the distal root lobe, but otherwise this face is not differentiated. The upper anterior teeth have well-defined root lobes that are asymmetrical, with the anterior lobe being longer than the posterior. The root is expanded to form a lingual protuberance, but this is not as distinct as in the lower teeth. The profile of the root of the three presumed upper anterior teeth is rather different; in the first upper, the root lobes are short, and the anterior lobe somewhat recurved to the posterior, whilst the roots of the second and third teeth are strongly asymmetrical with a longer anterior lobe. The root of the presumed third upper tooth is somewhat more labiolingually compressed than that of other anterior teeth, and the linguo-basal root face is more clearly differentiated and flatter, thus resembling the root of the upper lateral teeth.

Teeth presumed to be from upper lateral positions show some morphological variation, with the first upper anterior being clearly differentiated from the rest. Upper lateral teeth are strongly asymmetrical, with the cusp strongly inclined to the posterior. The cusp comprises up to half of the total height of the tooth, being slender, straight and tapering smoothly to the tip. There is no lingual curvature other than in the probable anteriormost teeth, where there is a gentle sigmoidal curve. The labial face of the cusp is almost flat, and a continuous cutting edge is present. At the base of the main cusp is a pair of very small to (in the anteriormost teeth) incipient lateral cusplets, which are triangular in profile and of similar size in both anterior and posterior positions. The lingual face of the crown is convex, nearly semicircular in section in most teeth but more lingually expanded in the anteriormost teeth. There is a clear lingual neck. The labial face of the crown extends along about half of the upper edge of the root lobes, being flat and merging with the root labial face. The root lobes are asymmetrical, becoming less so in more posterior teeth. The anterior root lobe it slender and parallel sided, with a rounded or slightly pointed apex. The posterior root lobe is typically about half the length of the anterior, and has a more angular termination. In the anteriormost teeth, the most distal part of the posterior root lobe is twisted lingually. The root is at its widest at the point of a poorly developed lingual protuberance, and then tapers gradually towards the tips of the root lobes, resulting in the root lobes being very labiolingually compressed and having a wide and flat linguo-basal root face. The root of the anteriormost teeth is of the same general shape, but with very little labiolingual compression, resulting in a far more robust root. There is a prominent foramina on the lingual protuberance, and small foramina are present across the surface of the root of all teeth.

Upper intermediate teeth are similar in overall shape to those from the mid part of the upper lateral files. They differ in being smaller, reaching about half the maximum size, having a more robust main cusp and having a pair of well-developed lateral cusplets. Anterior and posterior cusplets are of similar size and triangular in profile.

Presumed lower lateral teeth are in many respects similar to anterior teeth. The teeth are relatively symmetrical, except in posterior files where they are rather inclined to the posterior. The cusp is straight and slender, with a very slight sigmoidal curvature and comprises about half of the total height of the tooth. The cusp labial face is weakly convex, and separated from the strongly convex lingual face by a narrow but continuous cutting edge. There are no lateral cusplets, and the base of the labial face of the crown extends over the upper part of the root lobes, where there is no basal overhang. There is a clear neck at the lingual base of the crown. The outer edges of the root lobes extend almost in continuation of the angle of the outer edges of the cusp, giving the teeth a rather compressed ‘Y’ shaped profile. The root lobes are clearly separated and rather gracile and parallel sided. There is a well-developed lingual protuberance, and below this the lingual side of the root lobes are somewhat expanded lingually, with no clearly defined linguo-basal root face. There is a single, well-developed, foramen at the apex of the lingual protuberance, and numerous small foramina elsewhere on the root.

Remarks.  Teeth of Telodontaspis agassizensis sp. nov. are present in the Cenomanian of Colorado (Shimada et al. 2006), and it is considered likely that this species has been under recorded because of confusion with teeth of juvenile Cretoxyrhina.

Family ANACORACIDAE Casier, 1947

Genus SQUALICORAX Whitley, 1939

Type species. Corax pristodontus Agassiz, 1843 from the Maastrichtian of the Netherlands.

Squalicorax curvatus (Williston, 1900)
Plate 7, figures 1–23; Plate 8, figure 2

Figure EXPLANATION OF PLATE 7.

Figure EXPLANATION OF PLATE 7.


Figs 1–23. Squalicorax curvatus (Williston, 1900); all ×4.5. 1–2, P2989.153, parasymphyseal tooth. 1, labial view. 2, lingual view. 3–4, P2989.154, ? upper anterior tooth. 3, labial view. 4, lingual view. 5–6, P2989.155, ? upper anterior tooth. 5, labial view. 6, lingual view. 7–8, P2989.156, ? upper anterolateral tooth. 7, labial view. 8, lingual view. 9–10, P2989.157, ? upper anterolateral tooth showing occlusion damage. 9, labial view. 10, lingual view. 11, P2989.158, ? lower anterior tooth, labial view. 12, P2989.159, ? lower anterior tooth, labial view. 13–14, P2989.160, ? lower anterolateral tooth. 13, labial view. 14, lingual view. 15–16, P2989.161, ? upper lateral tooth. 15, labial view. 16, lingual view. 17–18, P2989.162, posterolateral tooth. 17, labial view. 18, lingual view. 19-20, P2989.163, posterolateral tooth. 19, labial view. 20, lingual view. 21–22, P2989.164, posterior tooth. 21, labial view. 22, lingual view. 23, P2989.165, posterolateral tooth, labial view.

  • 1900 Corax curvatus Williston pl. 30, figs 7–8.

  • 1990 Squalicorax falcatus (Agassiz); Case et al., p. 1091, fig. 10a–p, p. 1092, fig. 11a–b.

  • ?1993 Squalicorax curvatus (Williston, 1900); Welton and Farish, p. 116, figs 3–4.

  • 1993 Squalicorax falcatus (Agassiz); Williamson et al., p. 457, fig. 7.4–7.5.

  • 1999 Squalicorax sp. (group falcatus); Cappetta and Case, p. 63, pl. 6, figs 4–9.

  • 1999 Squalicorax curvatus (Williston); Cappetta and Case, p. 65, pl. 7, figs 6–8.

  • 1999 Squalicorax sp. Cumbaa and Tokaryk, p. 61, fig. 5 (pars; 5 teeth in right 2 columns).

  • ?2001b Squalicorax sp. cf. S. curvatus (Williston); Cicimurri, p. 185, fig. 5g.

  • 2006 Squalicorax falcatus (Agassiz); Cumbaa et al., p. 146, fig. 4.9.

  • 2006 Squalicorax curvatus (Williston); Shimada et al., p. 9, fig. 8.2–8.4.

  • 2006 Squalicorax falcatus (Agassiz); Shimada et al., p. 9, fig. 8.5–8.9.

  • 2006 Squalicorax sp. Shimada et al., p. 9, fig. 8.10–8.14.

  • 2008 Squalicorax sp. Cook et al., p. 1189, fig. 5B.

Material.  About 800 teeth studied including P2989.153–P2989.166.

Description.  Teeth of this species are up to 14 mm wide and show considerable gradient monognathic heterodonty as well as, in anterior files, dignathic heterodonty. By comparison with modern lamniform and carcharhiniform sharks, it is presumed that teeth with more slender and erect cusps which are associated with a more swollen labial overhang with a somewhat ‘W’ shaped basal edge of the crown are from lower anterior positions.

The crown of the teeth varies from 75 to 200 per cent as wide as high depending on jaw position, with only extreme anterior teeth being higher than wide. The crown comprises a main cusp and a small but clearly defined distal heel, the latter being between one fifth and one-quarter of the total width of the tooth. The main cusp is never symmetrical, other than in some parasymphyseal teeth, and is inclined to the posterior to a varying degree. The labial face is faintly convex, with a strongly convex lingual face, neither with any ornamentation. The anterior edge of the main cusp is very variable in shape. In most teeth, the basal part of the anterior edge is straight and at a lower angle than the bulk of the edge, with a clear angular contact between the two parts of the edge. In presumed lower teeth, this basal section is shorter and less well defined than in upper teeth. After this the anterior cusp edge ranges from straight to clearly convex, but is faintly convex in most teeth. The apex of the cusp typically forms and angle of 50–60 degrees. The posterior edge of the cusp is straight to slightly convex and varies from near vertical (in lower anterior teeth and some larger posterolateral teeth) to strongly overhanging (in most teeth). Only rare presumed upper anterolateral teeth have the cusp apex reaching beyond the posterior margin of the rest of the tooth. The distal heel is low and has a straight upper edge and convex posterior edge. There is a sharp angle between this and the main cusp of between 80 and 125 degrees, only being less than 90 degrees in some lower lateral teeth. Continuous serrations are present over the cusp and distal heel; these get smaller towards the tooth apex but are otherwise very regular, with between 5 and 7 serrations per millimetre. The serrations are roughly semicircular in profile and symmetrical, with no sign of secondary serrations. The base of the labial face of the crown extends down over the upper third to half of the root. In presumed upper teeth, the labial base of the crown clearly overhangs the root with a straight to slightly concave basal edge, without flaring towards the base. The base of the labial crown face of lower teeth extends further in the anterior and posterior parts of the tooth than in the centre, giving a rather ‘W’ shaped profile in some teeth. There is a prominent overhang along all of the labial crown base, but it is particularly evident where the crown reaches its lowest points, where the crown edge is flared labially to form a narrow ledge. The lingual base of the crown has a very obvious neck, which is of a relatively constant height across the width of the tooth. The roots of all teeth are close to symmetrical and are robust and thick. The root lobes are poorly defined, with an angle of 100–140 degrees between the anterior and posterior parts of the root. The root is of similar width to the crown, but the relative width of root and crown differ greatly with jaw position. The ends of the root lobes are commonly rounded, but the anterior root lobe may be more sharply pointed in lateral teeth, whilst a small linguo-distally projecting boss is present at the posterior of the lingual face of many lateral teeth. The labial root face is high and flat, and may be somewhat concave in the central part. There is a clear but rounded edge between this and the linguo-basal root face, which is quite flat. The lingual face of the root also forms a clear but rounded edge with the linguo-basal root face, and is flat and of a constant height across the width of the tooth. The central part of the lingual side of the root is rather swollen, and extends further lingually than the rest of the tooth. There is a small but obvious foramen close to the junction of the lingual and linguo-basal root faces in some teeth, but these are in the minority. There is a row of large and obvious foramina just below the base of the labial face of the crown in all teeth, and small and irregular foramina are present across all faces of the root. The tip of the cusp and ends of the root lobes are slightly bent labially so that the tooth has an overall concave labial face in most teeth.

Discussion.  The assemblage of teeth assigned to this species includes a quite diverse range of morphologies, but these all fit well within a single reconstructed dentition. Similarities in the root, serration, proportions and size of the teeth also suggest the presence of only a single species. The type material of Squalicorax curvatusWilliston, 1900 comprises two teeth, both of which compare well to teeth described here, and probably represent anterolateral and posterolateral positions. Subsequent descriptions of Squalicorax from the northern part of the Western Interior Seaway have recognized two morphotypes, and have either included all in S. falcatus Agassiz, 1843 (e.g. Case et al. 1990) or have separated them into S. falcatus and S. curvatus (e.g. Cumbaa et al. 2006; Shimada et al. 2006). Although some teeth can readily be placed into one of these morphotypes, others cannot, and Shimada et al. (2006) comment that the teeth they identify as S. falcatus appear to grade into S. curvatus and S. sp. (the last probably representing lower anterior teeth as described here).

It is now recognized that the diversity of anacoracids is rather higher than was previously appreciated (e.g. Cappetta and Case 1999; Siverson et al. 2007), and some names, especially Squalicorax falcatus, have been used for a number of different species. The holotype of S. falcatus (see Siverson et al. 2007) falls outside the morphological range of the material described here, having a less clearly defined distal heel, high cusp with smoothly convex anterior edge and probably smaller serrations and more labiolingual compression. Although there has been confusion between S. curvatus and S. baharijensisStromer, 1927 (e.g. Welton and Farish 1993; see Siverson et al. 2007), most teeth of S. curvatus are considerably more erect and have a shorter cusp, whilst presumed lower teeth are higher and have a shorter and wider cusp with a more continuously deep lingual neck.

Squalicorax curvatus was taken as the type species for the genus PraeptychocoraxGlickman, 1980, but the genus is poorly defined and appears to be largely based on the supposition that it is ancestral to Ptychocorax Glickman and Istchenko inGlickman, 1980, and is here considered invalid.

Genus PALAEOANACORAX Glickman and Shvazhaite, 1971

Type species. Palaeoanacorax volgensis Glickman in Glickman and Shvazhaite, 1971 from the Cenomanian of Russia.

Remarks.  The genus Palaeoanacorax was erected by Glickman (Glickman and Shavzhaite 1971) for a group of anacoracid species defined both on their morphology and stratigraphical position. Although the definition of a genus on stratigraphical grounds should be considered invalid, the group of species, exemplified by Palaeoanacorax volgensis Glickman, 1971, included into this genus are morphologically distinct from SqualicoraxWhitley, 1939. Teeth of Palaeoanacorax differ from those of Squalicorax s.s. in having a lower crown with well-defined cusp, thicker and lower root which is overhung by the crown labially, greater degree of heterodonty and serrations that are incipient, irregular or missing altogether. Whilst Glickman (1971) did not include Squalicorax falcatus and related forms into Palaeoanacorax, they were included into the genus by Sokolov (1978) in some parts of a paper that elsewhere retains them in Squalicorax (of current usage).

It is considered here that Palaeoanacorax is a valid genus and includes Squalicorax pawpawensisSiverson et al., 2007, Squalicorax microserratodonShimada, 2008, Squalicorax primulusMüller and Diedrich, 1991, Squalicorax priscoserratusSiverson et al., 2007 and Palaeoanacorax volgensis Glickman, 1971, as well as a number of unnamed species from the Cenomanian (e.g. Siverson 1997), Turonian/Coniacian (Cappetta and Case 1999), Santonian and Campanian (Underwood and Ward 2008). Eoanacorax Glickman, 1971 is probably a separate valid anacoracid genus containing a number of Albian and Cenomanian species possessing elongate cusps, a very reduced distal heel and no serrations.

Palaeoanacorax aff. pawpawensis (Siverson et al., 2007)
Plate 8, figures 3–5; Text-figure 5A–M

Figure TEXT‐FIG. 5..

Palaeoanacorax aff. pawpawensis (Siverson et al., 2007); all ×8. A–B, P2989.167, anterior tooth. A, labial view. B, lingual view. C–D, P2989.168, lateral tooth. C, labial view. D, lingual view. E–F, P2989.169, lateral tooth. E, labial view. F, lingual view. G, P2989.170, posterolateral tooth, labial view. H–I, P2989.171, exceptionally gracile anterolateral tooth. H, labial view. I, lingual view. J, P2989.172, anterior tooth, labial view. K, P2989.173, anterior tooth, labial view. L–M, P2989.174, anterolateral tooth. L, labial view. M, lingual view.

  • ?2001b Squalicorax volgensis (Glickman); Cicimurri, p. 185, fig. 5h.

  • aff. 2007 Squalicorax pawpawensis (Siverson et al., 2007); text-fig. 2A, pl. 1, figs 1–26.

Material.  About 6500 teeth studied including P2989.167–P2989.176.

Description.  The teeth of this species are small, the largest being 8.5 mm wide. There is considerable monognathic and probably minor dignathic heterodonty, with teeth possessing more slender and erect cusps being from the lower jaw. Parasymphyseal teeth are small, ranging from one to three millimetres high, close to symmetrical and more than twice as high as wide. The larger parasymphyseal teeth are similar to other anterior teeth other than being considerably more laterally compressed and, in some cases, possessing a heel or incipient cusplet on both anterior and posterior sides of the teeth. Smaller parasymphyseal teeth comprise a conical to slightly lingually curved cusp projecting from an oval to near spherical root. In these teeth, the cutting edge may be severely reduced or even absent.

Of the remainder of the teeth, the crown varies from 75 to 200 per cent as wide as high depending on jaw position, with only extreme anterior teeth being higher than wide. The main cusp is strongly inclined to the posterior in all but the most anterior teeth and is followed by a small but clearly defined distal heel, the latter being between one sixth and one fifth of the total width of the tooth. The main cusp is inclined to the posterior, weakly in the most anterior teeth, but very strongly, with the anterior cutting edge being almost horizontal, in posterolateral teeth. The labial face is faintly convex to flat, with a strongly convex lingual face, neither with any ornamentation. The anterior edge of the main cusp is convex towards the base, becoming straight or weakly concave higher up. The apex of the cusp typically forms and angle of 35–60 degrees, being more acutely pointed in presumed lower teeth. The posterior edge of the cusp is straight to very faintly convex. In all teeth there is some degree of overhang of the main cusp over the distal heel. In more erect anterior teeth, the apex of the main cusp extends as far to the posterior as the rear edge of the tooth, but this is not the case with most teeth. The distal heel is very low, with the upper edge typically sloping downwards from its anterior end, and evenly convex. A continuous cutting edge extends along the main cusp and distal heel. True serrations are not seen on any teeth, but faint crenulations or incipient serrations are present on the anterior cutting edge of all teeth except some parasymphyseal teeth and some posterolateral teeth. These crenulations do not reach either the apex of the cusp or anterior edge of the cutting edge. The base of the labial face of the crown extends down over the upper half of the root, which it strongly overhangs. The labial base of the crown is gently concave in all teeth, and is weakly flared towards the posterior end in some teeth. The lingual base of the crown has a very obvious neck, which is highest below the main cusp. The roots of all teeth are gently curved, with a similar depth of the root (in lingual view) present along much of its length, resulting in a lack of clearly defined root lobes. The labial root face is low, being higher at the anterior and posterior ends than near the centre. There is a clear but rounded edge between this and the linguo-basal root face, which is smoothly convex, and not clearly differentiated from the low lingual root face. The central part of the lingual side of the root is rather swollen, and extends further lingually than the rest of the tooth. The roots of all teeth are heavily vascularized. There is a row of large and obvious foramina just below the base of the labial face of the crown in all teeth, and the overhanging base of the crown may be somewhat indented next to the foramina. Large and irregular foramina are present across the linguo-basal root face, often joining to form irregular, branching grooves in the root. Foramina are present on the lingual face of the root, but these are smaller than elsewhere and present within faint vertical grooves.

Discussion.  These teeth are very abundant and the large sample size allows the very high degree of heterodonty shown by this species to be recognized. There are large numbers of small parasymphyseal teeth recognized within the collection, suggesting that several files were present on at least one or possibly both, jaws. This has not been recognized in other anacoracid taxa (e.g. Shimada 2008). The smaller parasymphyseal teeth may easily be mistaken for teeth of co-occurring Cretomanta canadensisCase et al., 1990, but may be separated from them by, amongst other things, a less erect cusp and presence of a cutting edge.

Although very similar to the topotype material of Palaeoanacorax volgensis as figured by Siverson et al. (2007), the labial basal margin of the crown is gently concave, and not strongly scalloped. In addition, the majority of the teeth described here have a more slender cusp and wider distal heel than figured specimens of Palaeoanacorax volgensis. The same differences separate Palaeoanacorax aff. pawpawensis from the species present in the Australian Cenomanian (described as Squalicorax volgensis by Siverson (1996)) and specimens from the Turonian/Coniacian boundary of Texas (described as Squalicorax volgensis by Cappetta and Case (1999)). Palaeoanacorax aff. pawpawensis is most similar to P. pawpawensis (Siverson et al. 2007) (including specimens figured as P. volgensis by Cappetta and Case (1999) and Welton and Farish (1993)), but appears to differ in typically possessing a shorter and more robust cusp and larger but less well-developed serrations on the majority of teeth, in addition to having a smaller maximum size. Although it is probable that Palaeoanacorax aff. pawpawensis and P. pawpawensis are different species, there is considerable morphological overlap between populations of both, and it is at present not possible to clearly differentiate these taxa. Palaeoanacorax aff. pawpawensis is also very similar to P. primulus (Müller and Diedrich 1991), and there is a possibility that they could be conspecific, but the poor preservational and illustration quality of holotype and paratype specimens (Siverson et al. 2007) make comparisons difficult. Palaeoanacorax aff. pawpawensis teeth differ from those of the Albian P. priscoserratus (Siverson et al. 2007) and the Coniacian P. microserratodon (Shimada 2008) in the form of serration and root.

Order ORECTOLOBIFORMES Applegate, 1972
INCERTAE FAMILIAE

Genus ORECTOLOBOIDES Cappetta, 1977

Type species. Ginglymostoma parvulaDalinkevicius, 1935 from the ?Albian of Lithuania.

Orectoloboides angulatus sp. nov.
Plate 8, figures 6–18

Derivation of name.  After the angular overall appearance of the teeth.

Holotype.  P2989.178 (Pl. 8, figs 9–12).

Material.  Three teeth studied (P2989.177; P2989.179–P2989.180).

Diagnosis.  Teeth small, under 2 mm in greatest dimension, showing moderate heterodonty. Tooth crown of similar width to height. All teeth close to symmetrical, with a robust and conical main cusp (less than 1.5 times as high as wide) flanked by a single pair of short and robust lateral cusplets, with a second pair of incipient cusplets sometimes being present. A single ridge forming a sharp-edged keel is present on the labial face, and extends from half way up the main cusp to the base of a narrow but very prominent labial boss, sometimes bifurcating near the base. Other, shorter, ridges are present elsewhere on the crown but are always widely spaced and never join. Lingual crown face strongly convex with a very well-developed lingual protuberance at the base. Other than the labial boss, the crown does not strongly overhang the root. The root is wider and deeper than the crown, with a very well-developed nutritive groove seen in all teeth. The distal parts of the root lobes are somewhat recurved labially and have flared bases.

Description.  Teeth of this species are small and robust, with an overall very ‘angular’ appearance. All teeth are a similar height to width. The main cusp is conical and higher than wide with the base making up about half of the width of the tooth crown. This is flanked by a single pair of short and robust lateral cusplets, which may have a second pair of incipient cusplets on their outer margin. The lateral cusplets are about as high as wide and slightly divergent. A well-developed cutting edge runs from the outer edge of the tooth crown and over the cusplets, but does not reach the apex of the main cusp. The labial surface of the tooth crown extends over the labial face of the tooth for at least the same distance as the height of the lateral cusplets. A very prominent labial protuberance is present below the main cusp. This is roughly parallel sided with a rounded termination, and is about half of the width of the base of the main cusp. The labial face of all cusps is weakly convex. A very prominent, sharp-edged ridge extends from the tip of the labial protuberance to about half way up the main cusp. In one tooth, this bifurcated into two ridges on the labial protuberance Pl. 8, figs 13–15). Additional, short longitudinal ridges are present on the more lateral parts of the crown labial face. In the two larger teeth, they are short and very weak with two or three ridges being present below the lateral cusplets. On the two smaller teeth, these ridges are more strongly developed, with up to five on either side of the tooth. The lingual side of the cusps is strongly convex, and below the main cusp this becomes expanded downwards to form a lingual uvula. The uvula projects lingually to varying degrees, and extends downwards to the lingual end of the root nutritive groove. Other than at the point of the labial protuberance, the labial basal edge of the crown only weakly overhangs the top of the root. There is no crown overhang of the root lingually, and the basal lingual edge of the crown has a narrow smooth neck at the junction with the root. The root is bulky and slightly wider than the crown in all teeth. The root is very strongly bilobate, with a wide and deep nutritive groove extending for the whole depth of the root. The labial surface of the root lobes is laterally and labially flared basally, giving a rounded profile to the lateral edge of the root. The latero-labial face of the root lobes also flares downwards, especially on either side of the nutritive groove, where it forms a pointed lingual projection. There is a sharply angled edge of the basal face of the root all round. The basal face of the root lobes is smooth and only slightly convex. Other than at least one very large foramina within the nutritive groove, foramina are few but quite prominent, with two or three circular to oval foramina on each latero-labial root face and one to four on each basal root face.

Remarks.  Teeth of Orectoloboides angulatus sp. nov. are very similar to those of O. parvulusDalinkevicius, 1935, but differ in several ways. The cusps of O. parvulus are higher and more slender, with this being especially evident in lateral cusplets, where a second pair of clearly separated cusplets is often present (CJU, pers. obs.). In addition, teeth of O. parvulus appear to show a greater degree of heterodonty with the distinctive lateral tooth morphology (e.g. Cappetta 1977, fig. 2) not being recognized here. Teeth of O. multistriatusWerner, 1989 have a considerably finer and more densely spaced ornament. Teeth of O. angulatus sp. nov. are superficially similar to teeth of some sclerorhynchids, but differ in the presence of lateral cusplets, a strong ornament and a more arched and flared root.

Genus CRETORECTOLOBUS Case, 1978

Type species. Cretorectolobus olsoniCase, 1978, from the Campanian of Montana, USA.

Cretorectolobus robustus sp. nov
Plate 8, figures 19–22

Derivation of name.  From the relatively large and robust teeth compared to others of the genus.

Holotype and only specimen.  P2989.188 (Pl. 8, figs 19–22). This was collected as part of the Canadian Museum of Nature study and not from the same sub sample as the rest of the material described here.

Diagnosis.  Near symmetrical tooth with single erect cusp. Tooth considerably wider than high, with blade-like lateral crown extensions of similar width to root. Lateral crown extensions of uniform height without cusplets but noticeably arched to give convex occlusal surface. Occlusal cutting edge of lateral extensions sigmoidal in occlusal view. Labial protuberance prominent but narrow and parallel sided with rounded apex. Uvula tapering and quite weakly developed. Root low and somewhat extended lingually in region of uvula. Hemiaulacorhize root vascularization with well-developed small foramina on all faces of root except labial face.

Description.  The single tooth known is from a presumed lateral position and is 4.4 mm wide. The tooth has a general ‘squatinoid’ morphology, with an erect cusp at close to right angles from the flattened and triangular root. The cusp is triangular and has a height less than one third of the total tooth width and slightly linguo-posteriorly curved. The cusp is triangular with a convex labial surface and strong convex lingual surface. At its base, the cusp merges with lateral blades on both mesial and distal sides. These blades are of relatively constant height, but are somewhat curved with a convex occlusal surface with no incipient cusplets. The distal ends of the lateral blades are smoothly rounded. There is a well-developed cutting edge extending for the entire occlusal surface of the crown. When viewed occlusally, there is a distinct sigmoidal curvature to the cutting edge on the lateral blades. Below the labial face of the cusp is a well-developed labial protuberance which extends to at least the full depth of the root. This is narrower than the base of the cusp, parallel sided and with a rounded tip. A wide but shallow uvula is present on the lingual side of the tooth, extending from the base of the cusp to the lingual edge of the root. There is no ornament on the crown. Other than around the labial protuberance, there is no crown overhang of the root, but the crown-root contact is sharp and well defined. The root is low and triangular in basal view. The root is about three times as wide as the labiolingual depth, with a straight labial face and expanded lingually to the tip of the uvula. The labial root face is as wide as the crown and slightly flared at the base. There is a sharp but not angled contact between this and the basal face, which is broadly concave. The lingual root face is slopes from the base of the crown to a distinct contact with the basal face. There is a large foramen near the centre of the root basal face and another just below the lingual tip of the root. Small foramina are scattered across all faces of the root except the labial face.

Remarks.  A number of genera have been proposed for teeth with a general ‘squatinoid’ morphology from the Cretaceous, with different species being assigned to either the Orectolobiformes or the Squatiniformes. The tooth described here is assigned to the former because of the low and rather robust cusp, high lateral blades and a root that is only weakly expanded lingually. Cretorectolobus robustus sp. nov. differs from C. olsoniCase, 1978 from the Campanian of North America in having a more robust cusp, no incipient lateral cusplets, a more slender labial protuberance and more random spread of foramina over the root. C. gracilisUnderwood and Mitchell, 1999 from the British Albian and C. doyleiUnderwood et al., 1999 from the British Hauterivian have a far smaller maximum size then C. robustus sp. nov. C. gracilis also differs in having very reduced lateral blades and a higher root, whilst C. doylei has incipient lateral cusplets and a relatively high root. Teeth of species of the related genus CederstroemiaSiverson, 1995 are more robust overall, with a flattened and triangular cusp.

Superorder BATOMORPHII Cappetta, 1980b
Order RAJIFORMES Berg, 1940
Family RHINOBATIDAE Müller and Henle, 1838

Genus RHINOBATOS Linck, 1790s.l.

Type species. Rhinobatos rhinobatosLinnaeus, 1758; extant.

Remarks.  The genus Rhinobatos has been used for teeth and skeletons of a large number of extinct species of rhinobatid (e.g. Cappetta 2006). Although many taxa previously assigned to Rhinobatos have subsequently been moved to other genera, many fossil species of Rhinobatos remain, many of which will probably need to be moved to other genera in the future.

Rhinobatos’ cf. incertusCappetta, 1973
Text-figure 6A–H

Figure TEXT‐FIG. 6..

 A–H. ‘Rhinobatos’ cf. incertusCappetta, 1973; all ×40. A–D, P2989.181. A, occlusal view. B, lingual view. C, oblique view. D, basal view. E–H P2989.182. E, occlusal view. F, lingual view. G, oblique view. H, basal view. Figs I–U. Cretomanta canadensisCase et al., 1990; all ×25. I–J, P2989.183, fused tooth. I, labial view. J, oblique view. K–M, P2989.184. K, labial view. L, lateral view. M, occlusal view. N–O, P2989.185. N, lateral view. O, labial view. P–R, P2989.186. P, labial view. Q, lateral view. R, occlusal view. S–U, P2989.187. S, labial view. T, occlusal view. U, lateral view.

  • 1973 Rhinobatos incertus Cappetta, p. 508, figs 26–33.

  • 1973 Rhinobatos sp. Cappetta, p. 508, figs 18–25.

  • 1990 ?Rhinobatos sp. Case et al., p. 1093, figs 12–13.

  • 1993 Rhinobatos sp. Williamson et al., p. 458, fig. 8.

  • 1993 Rhinobatos incertus Cappetta; Welton and Farrish, p. 132, figs 1–2.

  • 2001a ?Rhinobatos incertus Cappetta; Cicimurri, p. 185, fig. 5X.

  • 2004 ?Rhinobatos incertus Cappetta; Cicimurri, p. 9, fig. 5J.

  • 2006 Rhinobatos sp. Shimada et al., p. 19, fig. 11.3–11.4.

  • 2007 Rhinobatos incertus Cappetta; Everhart, p. 230 (pars), fig 6B–D (non A).

Material.  Two teeth (P2989.181 and P2989.182).

Description.  Both teeth are less than 1 mm across and have low crowns. The teeth are similar in width to height and have a crown that is somewhat larger than the root. The labial face of the crown is weakly convex and rather wider than high, and somewhat lozenge-shaped, with rounded edges lingually and labiobasally and rather sharply angled lateral ends. There is no defined cusp, but the labial face of the crown is somewhat expanded above the lingual uvula to form an incipient cusp, although this is largely removed by wear in one specimen. The lingual face of the crown is angled at nearly right angles to the labial face, with an angled contact but without a defined cutting edge. The central half of the lingual face comprises a well developed and somewhat bulbous uvula. The uvula is somewhat tapered basally and extends about twice as far down the root lingual face as the lateral parts of the crown. Lateral uvulae are poorly developed, and comprise little more than the lingual crown face separated from the main uvula by a variably well-developed groove. The crown is unornamented. The crown strongly overhangs the root on all sides. The root is of a similar width to the crown and slightly displaced lingually. The root is strongly bilobate, with a wide and conspicuous nutritive groove. The linguolateral root faces flare basally from beneath the crown, and are relatively flat. The root basal faces are flat and slightly angled laterally. In basal view, each root lobe basal face is triangular, being of similar size in one tooth but rather asymmetrical in the other, where the nutritive groove is wider. There is at least one very large foramen within the nutritive groove, along with one small foramen on each linguolateral root face and several on each root lobe basal face.

Discussion.  The teeth seen here appear to be the same taxon as noncuspate teeth figured as Rhinobatos sp. by Cappetta (1973). This species co-occurs with the cuspate teeth that include the type material of R. incertusCappetta (1973), which it resembles in all but form of the occlusal surface. In all instances where cuspate teeth referred to, or resembling, R. incertus have been recorded, noncuspate teeth of the type recorded here are also present; in addition, where an idea of proportions is recorded (Cappetta 1973; Shimada et al. 2006), noncuspate teeth far outnumber cuspate. It is therefore considered here (as by Welton and Farish 1993 and Everhart 2007) that Rhinobatos sp. and R. incertus are conspecific, with the cuspate morph representing teeth of breeding males.

Despite the poor quality of figures of some specimens referred to this species (e.g. Case et al. 1990; Cicimurri 2001a, 2004), teeth appear to be widespread within the Western Interior Seaway, and range from Upper Albian to at least Coniacian (Everhart 2007). This species does not, however, appear to be present in Europe or further afield (e.g. Herman 1977; CJU, pers. obs.).

?BATOMORPHII incertae sedis

Genus CRETOMANTA Case et al., 1990

Type species. Cretomanta canadensisCase et al., 1990 from the basal Turonian of Saskatchewan (published incorrectly as Coniacian).

Cretomanta canadensisCase et al., 1990
Text-figure 6I–U

  • 1990 Cretomanta canadensis Case et al., p. 1093, fig. 14a–c.

  • 1993 ?Rhincodontidae Welton and Farish, p. 86, figs 1–3.

  • 2001a Cretomanta canadensis Case et al.; Cicimurri, p. 185, fig. 5S–T.

  • 2004 Cretomanta canadensis Case et al.; Cicimurri, p. 9, fig. 5O.

  • 2006 Cretomanta canadensis Case et al.; Shimada et al., p. 19, fig. 11.7–11.8.

Material.  Forty-seven teeth studied including P2989.183–P2989.187.

Description.  Teeth of this species are up to 1.5 mm high and are relatively homodont. The single cusp, or in the case of one specimen, each of two equal sized cusps, comprises about half of the total height of the tooth and is erect, being either near vertical (relative to the root basal face) or slightly inclined labially. The cusp is round in cross-section to slightly laterally compressed, and lacks any cutting edge. The cusp is one to 1.5 times as high as deep and strongly curved lingually, with a curvature on the labial edge of 45–70 degrees. There is a well-developed collar at the base of the cusp that is somewhat constricted, with the thickest part of the cusp being close to the centre, tapering to a slender and sharp point.

The root is rounded and globular. In smaller teeth, it is near spherical, but in most teeth the root is somewhat expanded lingually. The labial face of the root is near vertical, whereas other faces are flat to slightly concave, with the root widening downwards and lingually to gently convex basal face. Small foramina are spread across the root, but are concentrated on the mid part of the lateral root faces and on the basal face.

In broken or transparent teeth, it is possible to see a slender, tubular, pulp cavity running most of the length of the cusp. Small tubules branch from this and are obvious within the dentine.

Discussion.  The affinity of Cretomanta canadensis is very uncertain, largely because of the extremely convergent and conservative morphology of teeth of microphagous chondrichthyans. The overall morphology of the teeth is extremely similar to that of the reduced parasymphyseal teeth of Palaeoanacorax aff. pawpawensis. Teeth of C. canadensis do, however, differ in having a more erect and strongly curved cusp, a slightly fusiform labial cusp profile, the lack of a cutting edge on all teeth, and a narrow pulp cavity. The form of vascularization suggests that a lamniform affinity is not supported (contraCappetta 2006), but may suggest a batomorph affinity. The presence of a ‘double’ tooth is similar to those present where row splitting occurs in the dentition of some batoids (e.g. Herman et al. 2000, textplate 5), and may further suggest a batoid affinity. Although the tooth morphology is not unlike that of some extant planktivorous batoids, it is likely that this is convergently derived and as such family level affinities are uncertain. Despite the morphology of the teeth suggesting planktivory, faint longitudinal scratches may be present, but it is not certain whether these are a result of wear against rigid food items or because of occlusion with teeth on the opposing jaw. Teeth of similar morphology as the type material of Cretomanta canadensis have been recognized (CJU, pers. obs.) in rocks ranging in age from Cenomanian to Maastrichtian (Noubhani and Cappetta 1997), but it is currently uncertain whether this comprises several separate species.

Palaeoecology

The assemblage recovered from the Bainbridge River bonebed represents a relatively low diversity assemblage dominated by pelagic predators. Although an abundance of lamniforms appears to be a common feature of Cretaceous assemblages from the Western Interior Seaway (e.g. Welton and Farish 1993; Williamson et al. 1993; Cappetta and Case 1999), the almost complete lack of small nectobenthic taxa in the Bainbridge River assemblage is exceptional. The elasmobranch fauna is associated with a very rich and diverse assemblage of actinopterygians, with remains of hesperornithiform birds also being common (e.g. Cumbaa et al. 2006). Other nonavian reptiles are relatively rare, with only plesiosaurs being regular finds. The vast majority of the vertebrates appear to be active predators, with teeth adapted for either clutching active prey or, more rarely, cutting larger prey. Durophagous taxa are relatively uncommon, although several species of Ptychodus and pycnodonts are present. Teeth of Ptychodus rarely appear to show wear, and so it is possible that the main food source is not the same, or as hard shelled, as that favoured by some Ptychodus species elsewhere. The abundant remains of small teleosts and possibly teeth of Cretomanta suggest that planktivores were common. The extremely low number of teeth of benthic batoids and orectolobids may be because of occasional transient individuals. This assemblage therefore represents a very high nutrient environment with a hostile sea floor.

Some of the species recorded here (Cretoxyrhina denticulata and Ptychodus ex. gr. decurrens) appear to have a global distribution, but the majority are more restricted in their range. Shallower water sites in the northern Western Interior Seaway share some of the species with the fauna described here (Case 2001; Cook et al. 2008) but contain several lamniform and batoid taxa not present here, and lack the Ptychodus. Comparisons of small tooth taxa are not possible because of different collecting regimes. Many of the taxa recorded here are also present (albeit previously unrecognized) at other sites within the offshore parts of the northern Western Interior Seaway (e.g. Cappetta 1973; Cicimurri 2001b; Shimada et al. 2006), which also contain Tethyan faunal elements not recorded at the Bainbridge River. The diverse chondrichthyan assemblages known from the southern Western Interior Seaway in Texas (e.g. Welton and Farish 1993; Cappetta and Case 1999) have little in common with those from the Bainbridge River, with only Squalicorax curvatus and ‘Rhinobatosincertus present within Cenomanian rocks of both regions but not seen outside the Seaway. This is consistent with evidence from other vertebrate groups for at least two distinct faunal provinces in the Western Interior Seaway (Nicholls and Russell 1990). In contrast, there are several taxa present in Texas that are also present in Egypt (Werner 1989), indicating a stronger Tethyan link for the Texas assemblage than for a north-south connection through the Western Interior Seaway.

The mid Cretaceous distribution of Archaeolamna ex. gr. kopingensis is strongly indicative of it as a cool water taxon, being also present in northern Europe (e.g. Biddle 1993; Vullo et al. 2007) and Australia (Siverson 1996; 1997) but absent in Texas. It is therefore likely that a marine connection between the northern Western Interior Seaway and Boreal Ocean existed at this time, allowing direct connection to cool waters elsewhere.

If wide ranging taxa are excluded, there are no species in common between the Bainbridge River and mid Cretaceous faunas of northern Europe (e.g. Müller and Diedrich 1991; Underwood and Mitchell 1999), and common European taxa appear to be completely lacking in the Western Interior Seaway. This may suggest that there was no direct connection in the Cenomanian between the northern Western interior Seaway and the Proto Atlantic across what is now Hudson Bay.

Acknowledgments

Acknowledgements.  Support for this research came from the Canadian Museum of Nature (CMN) and a Discovery Grant to SLC for student support from the Natural Sciences and Engineering Research Council of Canada and University of London Central Research Fund GLRP5 to CJU. The field research was conducted under Saskatchewan Heritage Palaeontological Resource Investigation Permit # 06-03P. Harold Bryant and Tim Tokaryk of the Royal Saskatchewan Museum ensured that the specimens were properly catalogued. Richard Day (CMN) and MSc. student Aaron Phillips (Carleton University) provided field and laboratory assistance, and CMN volunteer Dale Patten helped sort through the residue from acid preparation of the bonebed. David Ward greatly assisted with the photography and his knowledge was invaluable for reconstruction of the lamniform dentitions. Kenshu Shimada is thanked for his helpful discussions on WIS sharks. Michal Ginter, Jürgen Kriwet and David Ward are all thanked for their contributions and comments as reviewers of the manuscript.

Editor: Marcello Ruta

Ancillary