DASYATIDAE, Jordan and Gilbert, 1879

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 : 37

Family DASYATIDAE incertae sedis Dasyatoid indet.

Figure 12 N-O

2016 Dasyatis sp. 2 ; Merzeraud et al., p. 14-15, tab.

1.

Material. A dozen teeth, including those figured KEB 1-201, 1-202 ( Figure 12 N-O) from the KEB- 1 locality, Souar-Fortuna formations, Djebel el Kébar, Tunisia.

Description

Teeth are relatively large compared to previous taxa, reaching 2.5 mm long for the largest one. Showing a typical dasyatoid design, the dentition exhibits a gradual monognathic heterodont with high-crowned teeth, which decrease in size toward the commissure. Evidence of a dignathic heterodonty was not detected, the whole teeth being non cuspidate. The crown of teeth is smooth, except along the transverse keel ( Figure 12N 1 ) and sometimes on the labial face ( Figure 12O ) where it bears fine alveolar enameloid crests in occlusal view. The labial visor is extremely narrow in occlusal view, and the lingual border of the lingual face is primarily straight but also punctually sinuous ( Figure 12O ) compared to previous taxa. The lateral depression of the lingual face can be relatively large ( Figure 12N 1 ), thereby indicating a close interlocking teeth in staggered file. The root is particularly well elongated lingually with two root lobes long, well-detached by a wide nutritive groove where a small circular foramen opens centrally in basal view ( Figure 12N 2 ).

Remarks

Relatively scarce in the sample, teeth of these undefined taxa are different from those of previous described Dasyatidae . For instance, it is distinct from Middle-Late Eocene “D”. charlisae Case 1981 that possesses usual male teeth high crowned with strong ornamentation, conchoidal according Case (1981), covering completely the labial surface, from transversal keel to labial visor, and a narrower root compared to crown in lingual view. The presence of long and well-separated root lobes, a crown lingual face with marked articulate lateral depressions and lingual sinuous border could somewhat remind the dental traits characterizing teeth of the living Taeniurops (see Herman et al., 1998, 1999; Cappetta, 2012) or some Neogene representatives (Carrilo- Briceno et al., 2016, as cf. Taeniurops sp. ). However, the latter always have crown with labial face coarsely ornamented and none of these representatives present this peculiar fine alveolar ornamentation of the transverse keel.

Figures

FIGURE 1. Paleotemperatures (ice-free deep-ocean T°/ tropical sea surface T°) and Thermic events during the “doubthouse” conditions of Eocene period (from Cramwinckel et al., 2018 modified with events dating from Hollis et al., 2019). Stratigraphically and geographical locations of the main deposits with Elasmobranch associations along the southwestern Tethys. Abbreviations: DAK: Dakhla (Adnet et al., 2010), GEN: Genam (Zouhri et al., 2017, in press); AZ: Aznag (Tabuce et al., 2005) PM: Phosphate ores (see Noubhani and Cappetta, 1997), Morocco; GAF: Gafsa basin (see Arambourg, 1952); KEBAR: Kébar (this work and Adnet et al., 2019); MBK: Mabrouk (see Sweydan et al., 2019), Tunisia; EG: ElGedida (see Strougo et al., 2007); KM: KM11 (see Adnet et al., 2011) MT: Minqar Tabaghbagh (see Zalmout et al., 2012); BQ: Birquet Qarun QS: Quar et Sa; GE: Genahamm Fm.; MI: Midawara FM. from Wadi al Hitan, see Underwood et al., 2011), Egypt; QD: Qa Faydat al Dahikya, Jordania, see Mustafat and Zalmout, 2002).

FIGURE 2. Locality of KEB-1, Djebel el Kébar, Kasserine region, Tunisia. A, Simplified topographic map of Tunisia locating the Djebel el Kébar in central Tunisia; B, simplified stratigraphical position of fossiliferous level having yielded the fossil-bearing KEB-1 locality; C, photograph showing the typical badlands of variegated clays from the early Tertiary sequence of Djebel el Kébar. See Merzeraud et al. (2016) for precise details about geological settings.

FIGURE 12. A-C. Mecotrygon asperodentulus nov. gen nov. sp. A. anterior tooth KEB 1-188, A1. occlusal view, A2. Profile, A3. Basal view; B. lateral tooth KEB 1-189, B1. occlusal view, B2. labial view, B3. Profile; C. lateral tooth KEB 1-190, HOLOTYPE, C1. Occlusal view, C2. Lingual view, C3. Basal view, C4. Profile; D-M. Himantura souarfortuna nov. sp. D.?posterior tooth KEB 1-191, D1. Occlusal view, D2. Profile, D3. Basal view; E. antero-lateral tooth KEB 1- 192, occlusal view; F. anterior tooth KEB 1-193, F1. Occlusal view, F2. Labial view; G. antero-lateral tooth KEB 1-194, G1. Occlusal view, G2. Profile; H. anterior tooth KEB 1-195, occlusal view; I. lateral tooth KEB 1-196, occlusal view; J. A. anterior tooth KEB 1-197, occlusal view; K. lateral tooth KEB 1-198, K1. Occlusal view, K2. Basal view; L. A. anterior tooth KEB 1-199, occlusal view; M. lateral tooth KEB 1-200, occlusal view. N-O. Dasyatoid indet. N. antero-lateral tooth KEB 1-201, N1. Occlusal view, N2. Basal view; O. A. antero-lateral tooth KEB 1-202, occlusal view; P-Q. Arechia sp. P. lateral tooth KEB 1-203, occlusal view; Q. A. anterior tooth KEB 1-204, Q1. Occlusal view, Q2. Lingual view.