Mennerotodus, Zhelezko, 1994

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 : 14

Mennerotodus cf. M. parmleyi Cicimurri, Ebersole and Martin, 2020

Figure 5G–H

1861 Lamna (Odontaspis) Hoppei [sic] Ag.;

Rogovich, p. 49, pl. VII, figs. 3-10.

Material. One lower anterior tooth, NMNHU-G 391/ 71; one anterolateral tooth, NMNHU-G 391/88, Vyshhorod.

Description. The anterior tooth ( Figure 5G–H ) is quite small; it reaches 13.0 mm apicobasally and 7.4 mm mesiodistally. The main cusp is narrow, triangular, and slightly inclined distally. Cutting edges are sharp, smooth, and do not reach the base of the main cusp. There is a single pair of short, conical cusplets at the crown base. The labial face of the main cusp is smooth and flat while the lingual face is convex. Root lobes are elongated and almost of equal length.

The lateral tooth is much smaller, 6.5 mm high and 5.3 mm wide. It is morphologically similar to the anterior tooth, albeit has a shorter and relatively broader main cusp, cutting edges extending to the crown base, and root lobes are shorter but wider and more widely separated.

Remarks. The teeth resemble those of Mennerotodus Zhelezko, 1994 , and their morphological characteristics fit well into the emended diagnosis of this genus provided by Cicimurri et al. (2020). The specimens from Vyshhorod are close in overall morphology to teeth assigned to Mennerotodus parmleyi from the middle Eocene of the USA, but we only tentatively assign them to this species considering the absence of denticles between the cutting edges and lateral cusplets (which are characteristic for this species according to Cicimurri et al., 2020) and the small size of the studied sample. Mennerotodus parmleyi differs from M. glueckmani Zhelezko, 1994 from the middle Eocene of Kazakhstan in having much smaller teeth and the presence of a single pair of lateral cusplets on lateral teeth (Cicimurri et al., 2020). It further differs from the Paleocene (Danian) M. mackayi Cicimurri et al., 2020 in having a more conspicuous and extensively developed denticulation and a greater crown–root height ratio (Cicimurri et al., 2020).

Figures

FIGURE 5. Lamniform shark teeth from the middle Eocene deposits of Vyshhorod: A-F – Jaekelotodus trigonalis (Jaekel, 1895), lateral teeth NMNHU-G 391/62 (A-B), NMNHU-G 391/139/1 (C-D), NMNHU-G 391/139/2 (E-F); G-H – Mennerotodus cf. M. parmlei Cicimurri, Ebersole and Martin, 2020, lower anterior tooth NMNHU-G 391/71; I-L – Odontaspis winkleri Leriche, 1905, anterolateral tooth NMNHU-G 391/74 (I-J); lateral tooth NMNHU-G 391/79 (K-L); M-S – Isurolamna affinis (Casier, 1946), anterolateral tooth NMNHU-G 391/97 (M-N), anterior tooth NMNHU-G 391/94 (O-Q), lateral tooth NMNHU-G 391/95 (R-S). Labial view in A, C, E, G, I, K, M, O, and S, lingual view in B, D, F, H, J, L, N, P, and R, mesial view in Q.