Etmopterus sp.

Underwood, Charlie J. & Schlögl, Jan, 2013, Deep-water chondrichthyans from the Early Miocene of the Vienna Basin (Central Paratethys, Slovakia), Acta Palaeontologica Polonica 58 (3), pp. 487-509 : 496-498

Etmopterus sp.

Fig. 7A–G .

Material.—Seven lower and one upper partial and complete teeth including SNM Z 27463 to SNM Z 27468.

Description.—There is extreme dignathic heterodonty in this species, with multicuspate upper teeth and more blade−like lower teeth.

http://dx.doi.org/10.4202/app.2011.0101

The lower teeth are very small, being typically about 1 mm high, with rare larger specimens. They appear to show moderate monognathic heterodonty, with the exception of the rather wide posterior tooth, and possibly some degree of ontogenetic heterodonty. Teeth vary from rather higher than wide to slightly wider than high and all teeth show strong labio−lingual compression. The single cusp is very strongly inclined distally and comprises less than a quarter of the total height of the tooth. The cusp reaches to the distal edge of the tooth in all but the posterior tooth, and has weakly convex to straight mesial and distal cutting edges. Distally, the cusp overhangs a weakly developed and convex distal heel. The tooth below the cusp is roughly rectangular where preserved, but is rather variable in profile, with smaller, and presumably juvenile, teeth having a more angular profile. The mesial edge of the tooth is almost straight in the smallest teeth to faintly concave, but is very strongly so in a posterior tooth where a sharply angled notch is present. The distal edge of the tooth is variably convex in all teeth, being less so in smaller teeth. The basal edge of the tooth is straight or has a weak notch towards the distal end. A vertical concavity is present on the mesial side of the tooth labial face and a similar one on the distal side of the lingual tooth face. Other than in the concavity, enameloid covers large parts of the tooth labial face, where it has a convex lower edge that is deepest near the central part of the tooth. Three to six foramina are present along the lower edge of the labial enameloid covering, and these are rather irregular in their size, distribution and as to whether there is a short groove extending basally from the foramen. The lingual side of the tooth is largely flat, but is slightly swollen close to the base of the crown. The basal edge of the enameloid is straight and horizontal, terminating at a faint horizontal ledge. Two to four large foramina are present along this ledge, one of which appears to connect with a foramen about half way down the root face.

Only one broken upper tooth was recorded. This comprises a slender main cusp and at least two pairs of very long and slender lateral cusplets (as preserved). All three preserved cusps are at least three times as high as wide, and are nearly straight. The labial face of the cusps is faintly convex, and is separated from the strongly convex lingual face by a continuous cutting edge. The preserved root is bilobed and has root lobes that are roughly parallel sided. There is a poorly developed lingual protuberance.

Remarks.—This species differs from the Etmopterus sp. figured by Ledoux (1972) from the Miocene of France, in having lower teeth with a more rounded profile of the distal edge, a more rounded basal edge of the crown labial face which has more evenly spaced foramina, and a rather lower profile overall. Teeth have been figured from relatively few extant species of Etmopterus , but these, and specimens observed by one of us (CJU), cover examples of most of the species groups defined by Straube et al. (2010). Teeth of the species recorded here are very similar to those of the E. pusillus species group (of Shirai and Tachikawa 1993), with the relatively low root and rounded and symmetrical labial enameloid covering being apparently restricted to this species group. The low numbers of well preserved teeth are here considered insufficient for a species diagnosis, while there is the possibility that the material present here represents an extant species from which the dentition is currently unrecorded.

Figures

Fig. 7. Miocene squaliform sharks Etmopterus and aff. Miroscyllium teeth from Cerová section in Malé Karpaty, Slovakia. A–G. Etmopterus sp. A. SNM Z 27463, bed 17–18, lower tooth in labial (A1) and lingual (A2) views. B. SNM Z 27464, bed 17–18, lower tooth in labial (B1) and lingual (B2) views. C. SNM Z 27465, bed 17–18, lower posterior tooth in labial (C1) and lingual (C2) views. D. SNM Z 27465, bed 21–22, lower tooth in labial (A1) and lingual (A2) views. E. SNM Z 27466, bed 17–18, lower tooth in labial (E1) and lingual (E2) views. F. SNM Z 27467, bed 17–18, lower tooth in labial view. G. SNM Z 27468, bed 8–9, upper tooth in labial (G1) and lingual (G2) views. H–K. aff. Miroscyllium sp. H. SNM Z 27469, bed 17–18, lower symphyseal tooth in labial (H1) and lingual (H2) views. I. SNM Z 27470, bed 17–18, lower tooth in labial (I1) and lingual (I2) views. J. SNM Z 27471, bed 21–22, lower lateral tooth in labial (J1) and lingual (J2) views. K. SNM Z 27472, bed 17–18, lower tooth in labial (K1) and lingual (K2) views.