Heterodontus sp.

Kovalchuk, Oleksandr, Kriwet, Jürgen, Shimada, Kenshu, Ryabokon, Tamara, Barkaszi, Zoltán, Dubikovska, Anastasiia, Anfimova, Galina & Davydenko, Svitozar, 2023, Middle Eocene cartilaginous fishes (Vertebrata: Chondrichthyes) of the Dnieper-Donets Basin, northern Ukraine, Palaeontologia Electronica (a 32) 26 (2), pp. 1-37 : 10

Heterodontus sp.

Figure 4F

1861 Acrodus kioviensis n. sp.; Rogovich, p. 17, pl. II, figs. 4-10.

Material. Two lateral teeth, NMNHU-G 391/6, 391/ 7, Vyshhorod.

Description. The teeth are asymmetrical, equal in size, reaching 2 cm in length. The crown is low (up to 5 mm), with one cutting edge being straight, while the others are slightly convex and wrinkled. The occlusal surface is smooth due to abrasion. There are poorly developed radial folds that converge in the central part of the crown. The basal surface of the root is flat.

Remarks. Seven isolated teeth were collected and described by Rogovich (1861) from the Eocene deposits of Vyshhorod. A new species— Acrodus kioviensis —was erected based on these specimens, only two of which are now present in the collection of NMNHU-G. Nevertheless, the teeth share some diagnostic characters of heterodontiform sharks (in particular, the genus Heterodontus ) albeit resemble those in acrodontids due to a dental convergence (Cappetta, 2012). Representatives of the family Acrodontidae existed in Mesozoic seas and went extinct no later (if not earlier) than the Paleocene (Cook and Ramsdell, 1991). We refrain from assigning the specimens considered to a particular species, although we assume that this should be Heterodontus vincenti (Leriche, 1905) or another morphologically similar Eocene representative of this genus.

Figures

FIGURE 4. Hexanchiform, heterodontiform and lamniform shark teeth from the middle Eocene deposits of Vyshhorod: A-C – Hexanchus agassizi Cappetta, 1976, upper anterolateral tooth NMNHU-G 391/21/2 (A), lower lateral teeth NMNHU-G 391/21/3 (B) and NMNHU-G 391/21/4 (C); D-E – Notorynchus kempi Ward, 1979, upper anterolateral tooth NMNHU-G 391/20 (D), lower lateral tooth NMNHU-G 391/21/1 (E); F – Heterodontus sp., lateral tooth NMNHU- G 391/6; G-M – Striatolamia macrota (Agassiz, 1843), upper lateral teeth NMNHU-G 391/105 (G-H), NMNHU-G 391/ 54 (I-J), NMNHU-G 391/55 (K-L), upper posterior tooth NMNHU-G 391/92 (M); N-O – Brachycarcharias lerichei (Casier, 1946), lower lateral tooth NMNHU-G 391/52. Lingual view in A, H, J-K, M, and O, labial view in B-G, I, L, and N.