Eosqualiolus skrovinai, Underwood & Schlögl, 2013

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 : 494-496

Eosqualiolus skrovinai sp. nov.

Fig. 6A–G.

Holotype: SNM Z 27456 , lower tooth.

Etymology: In honour of Michal Škrovina, who was the first person who encouraged one of us (JS) with our palaeontological interests.

Type locality: Cerová−Lieskové, Vienna Basin, Slovakia.

Type horizon: Lakšárska Nová Ves Formation, late Karpatian (equivalent to latest Burdigalian), Miocene.

Material.—Nine lower and five upper partial and complete teeth including SNM Z 27455 to SNM Z 27461.

Diagnosis.—Extreme dignathic heterodonty present. Lower teeth with high cusp comprising nearly half of total tooth height. Cusp triangular with straight edges, inclined distally but not extending distally of short but well differentiated and semicircular distal heel. Tooth below cusp of similar height and width. Enameloid on labial face extends at least three quarters of distance to basal edge. A major labial foramen is present just above base of enameloid in centre of tooth, with a vertical groove below extending to root basal edge, forming a distinct notch on basal edge. A single smaller foramen is present behind main one. Major curved concavity marks mesial edge of enameloid below anterior part of cusp. Mesial profile of root with concavity below mesial end of cusp with swelling immediately below that. Tooth thickest at swollen horizontal ridge at base of enameloid on lingual face. Well developed concavity present below distal heel on lingual face. Upper teeth slender with single elongate cusp comprising over half of tooth height. Cusp weakly inclined distally and faintly sigmoidal. Cusp biconvex with continuous cutting edges that reach base of cusp. On labial face, base of cusp bifurcates into two short ridges on top of root lobes. These lobes have an acute edge and several short but sharp−edged ridges are present. Root low and flat−based, slightly asymmetrical, with short and rounded root lobes giving “heart−shaped” basal profile. Weak lingual protuberance is present with a large terminal foramen.

Description.—There is extreme dignathic heterodonty with slender upper teeth and triangular and blade−like lower teeth.

The lower teeth are only one well preserved tooth and several damaged teeth. These are larger than those of co−occurring squaliforms, reaching 3 mm in height. Despite the small number of specimens, there appears to be limited monognathic heterodonty. There is a strong labio−lingual compression and a well developed cutting edge is present along the occlusal edge of the tooth. The single cusp comprises nearly half the total tooth height and is somewhat erect, with the distal edge being only slightly distally inclined. Both mesial and distal edges of the cusp nearly straight, other than near the base of the mesial edge where a small concavity may be present in some teeth. The cusp does not overhang the distal edge of the tooth, and there is a strongly convex distal heel below it. The

UNDERWOOD AND SCHLÖGL—MIOCENE DEEP−WATER SHARKS FROM SLOVAKIA 495

1 mm (H)

tooth below the cusp is roughly square, with a weakly convex distal edge and irregularly concave mesial edge. There is a weak notch on the basal edge of the tooth below the main labial foramen. The mesial edge of the root is rather lobate, with a small swollen region about a third of the way down the root edge. Enameloid, reaches close to the base of the tooth on the labial side. There is a major concavity on the mesial side of the tooth, the distal edge of which is strongly indented and weakly overhung by enameloid. This concavity lacks enameloid and has a semicircular upper edge. Several small foramina are present along the upper part of the edge of this concavity. A very well developed foramen is present at the base of the enameloid, with a shallow vertical groove being present between this and the notch on the tooth basal edge. Up to three small foramina are present distally. The lingual side of the tooth is largely flat, but thickens slightly to form a faint horizontal ridge on the upper part of the tooth. There is a deeply indented region below the distal heel. The basal edge of the enameloid is straight with a major foramen just below the basal edge of the enameloid in the central part of the tooth

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

face; a small foramina may also be present to the anterior of this.

The upper teeth are slender and about 2 mm in height and show a low degree of heterodonty. Teeth are considerably higher than wide and comprise a single cusp and a weakly bilobed root. The cusp is straight to very faintly sigmoidal and rather inclined distally and is well over twice as high as wide. There is a continuous cutting edge separating the weakly convex labial face and more strongly convex lingual face. At the base of the labial side of the cusp is a bifurcating ridge that extends along at least half of the length of the root lobes. There are a number of rather short and irregular enameloid folds present both on these ridges and on the base of the crown between them. The root is quite robust and possesses two root lobes that are short but clearly differentiated, with a sharp internal angle and have rather angular terminations. The base of the root is flat but there is no sharp division between this and the labial face. There is a very large foramen at the base of the crown between the two crown lobes on the labial side, and a small foramen at the weak lingual protuberence at the top of the root. One or more small lateral foramina may also be present.

Remarks.— Eosqualiolus aturensis Adnet, 2006 from the Eocene of France is very similar to E. skrovinai sp. nov., especially as regards the lower teeth. Lower teeth of E. aturensis differ from those of E. skrovinai in having a weakly concave mesial edge to the cusp and a straighter mesial edge to the root. The upper teeth of E. aturensis are more slender than those of E. skrovinai , and lack a complete cutting edge and the ridged ornament on the labial face of the crown as well as having a less “heart−shaped” basal face. Specimens of lower and upper teeth from the Miocene of Jamaica, figured as Squaliolus sp. and Scymnodon aff. obscurus ( Vaillant, 1888) respectively by Underwood and Mitchell (2004), represent a different, but possibly closely related species, as does the material described as “Symnorhinidae indet” by Ledoux (1972); see also Adnet et al. (2006b). In addition to being far larger, the lower teeth of these species have a higher and more angular root that is mesially displaced. It is unclear whether these would be referable to Eosqualiolus or an additional related genus.

Stratigraphic and geographic range.—Eocene to Miocene, Tethyan Atlantic.