Hemiscyllium sp.

Adnet, Sylvain, Marivaux, Laurent, Cappetta, Henri, Charruault, Anne-Lise, Essid, El Mabrouk, Jiquel, Suzanne, Ammar, Hayet Khayati, Marandat, Bernard, Marzougui, Wissem, Merzeraud, Gilles, Temani, Rim, Vianey-Liaud, Monique & Tabuce, Rodolphe, 2020, Diversity and renewal of tropical elasmobranchs around the Middle Eocene Climatic Optimum (MECO) in North Africa: New data from the lagoonal deposits of Djebel el Kébar, Central Tunisia, Palaeontologia Electronica (a 38) 23 (2), pp. 1-62 : 23-24

Hemiscyllium sp.

Figure 8H

Material. Less than 10 teeth and fragmentary cusp from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia, and including the figured specimen KEB 1-151 ( Figure 8H ).

Description

The teeth are small (less than 2 mm in length), symmetrical to slightly asymmetrical ( Figure 8H ) depending of the file position. The crown always possesses a long and wide sharply-pointed central cusp, which is angled slightly distally in lateral tooth files. The main cusp is never flanked by pairs of lateral cusplets but by oblique straight heels. A moderate labial apron is developed on the crown margin and substantially overhangs the root. There is no ornamentation of the crown enameloid. The mesial and distal lobes of the root do not extend beyond the mesial and distal heels of the crown.

Remarks

With teeth weakly asymmetrical, possessing a flat labial face of crown, a large cusp and no developed lateral triangularly-shaped cusplets, these teeth belong preferentially to Hemiscyllium rather than to Chiloscyllium according to Herman (1977) and Herman et al. (1992). Few fossil species are known during the Paleogene, such as Hemiscyllium bruxelliensis (Herman 1977) and Hemiscyllium tailledisensis Adnet, 2006 , from Early-Middle Eocene deposits of the North Atlantic. Teeth of both contemporaneous species are clearly distinguishable from those of KEB-1 by their peculiar lower main cusp and sometimes, the presence of well-defined lateral cusplets in anterior teeth (e.g., H. bruxelliensis ). However, the material is too scarce to precise the species attribution. Strougo et al. (2007) and Underwood et al. (2011) have also reported the rare presence of this genus in EG, MI and BQ in Egypt.

Figures

FIGURE 8. A-C: Nebrius sp. A. Anterior tooth KEB 1-144, A1. Labial view, A2. Lingual view, A3. profile; B. Antero-lateral tooth KEB 1-145, B1. Labial view, B2. Basal view; C. Lateral tooth KEB 1-146, C1. Labial view, C2. Lingual view; D-G: Stegostoma tethysiensis nov. sp. D. (HOLOTYPE) Anterior tooth KEB 1-147, D1. Labial view, D2. Lingual view, D3. Basal view; E. Antero-lateral tooth KEB 1-148, E1. Labial view, E2. Occlusal viex, E3. profile; F. Lateral tooth KEB 1-149, labial view; G. Posterior tooth KEB 1-150, labial view; H: Hemiscyllium sp. 8. Antero-lateral tooth KEB 1-151, labial view; I-N: Odontorythys pappenheimi I.?Anterior tooth KEB 1-152, I1. Profile, I2. Labial view; J.?Latero-posterior tooth KEB 1-153, lingual view; K.?Latero-posterior tooth KEB 1-154, profile; L.?Latero-posterior tooth KEB 1-155, profile; M.?Latero-posterior tooth KEB 1-156, profile; N.? lateral or posterior tooth KEB 1-157, N1. Profile, N2. Labial view, N3. Lingual view.