Hemipristis curvatus Dames, 1883

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 : 16

Hemipristis curvatus Dames, 1883 , Figure 7 A-C

Material. Consists of four teeth (including KEB 1- 133 to 1-135; Figure 7 A-C) and several broken upper and lower teeth from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.

Description

Although the fossil material is scarce or poorly preserved, upper teeth have a relatively high crown, which is compressed labio-lingually and slanted distally. The mesial cutting edge is convex with, in its median part, two very small denticles. The distal cutting edge is straight and forms an angle with an oblique distal heel. The latter is high and bears several well-developed denticles. The lingual face of the crown is convex, the root, partially unpreserved, bears a well-developed lingual protuberance, incised by a shallow groove. In labial view, the convex crown forms a bulge at its base, and strongly overhangs the low root. The anterior lower tooth has a relatively high, slender and straight cusp with sharp cutting edges that never reach its lower part. There is no denticle on the available material. The root, although incomplete, is massive, with short but well-developed lobes separated by a deep median nutritive groove.

Remarks

The morphology of teeth is similar to that of those from the Late Eocene of Fayum attributed to Hemipristis curvatus by Case and Cappetta (1990, figures 4, 80-81). Hemipristis curvatus is primarily known from all tropical seas during the late Middle-Late Eocene, from the Tethys seaway (e.g., Case and Cappetta, 1990; Mustafa and Zalmout, 2002; Underwood et al., 2011) to the Western Central Atlantic (Case and Borodin, 2000; Ebersole et al., 2019). However, Underwood et al. (2011) reported this species in MI (but not illustrated), when it is typically more common throughout the remainder of the Wadi al Hitan succession (see also Underwood et al. 2011, figure 5B and 5C from BQ), and especially since the GE (A–C) (around the Bartonian/Priabonian boundary). This new occurrence confirms the late Middle Eocene appearance of the genus Hemipristis in the Tethys seaway, and this material then represents one of the oldest figured report (with those of Ebersole et al., 2019 from the Bartonian of Alabama) of this famous lineage highlighted by its descendent, H. serra , reported since the Early Oligocene (e.g., Adnet et al., 2007; Van Vliet et al., 2017) until the Pleistocene of Alabama (Ebersole et al., 2017).

Figures

FIGURE 7. A-C: Hemipristis curvatus. A. Antero-lateral upper tooth KEB 1-133, A1. Lingual view, A2. Labial view; B. Lateral upper tooth of young specimen KEB 1-134, labial view; C. Anterior lower tooth of young specimen KEB 1-135, labial view; D-E: Moerigaleus sp. D. Lateral upper tooth KEB 1-136, D1. Lingual view, D2. Labial view; E. Lateral upper tooth KEB 1-137, E1. Lingual view, E2. Labial view; F-K: Leptocharias tunisiensis nov. sp. F. (HOLOTYPE) Antero-lateral lower tooth KEB 1-138, F1. Profile, F2. Lingual view, F3. Labial view; G. Antero-lateral upper tooth KEB 1-139, G1. Labial view, G2. Profile, G3. Lingual view; H. Anterro-lateral lower tooth KEB 1-140, labial view; I. Lateral lower tooth KEB 1-141, labial view; J. More lateral tooth KEB 1-142, J1. Labial view, J2. Lingual view, J3 occlusal view; K. Posterior tooth KEB 1-143, K1. Labial view, K2. Lingual view.