Carcharhinus, Blainville, 1816

Zouhri, Samir, Gingerich, Philip D., Khalloufi, Bouziane, Bourdon, Estelle, Adnet, Sylvain, Jouve, Stéphane, Elboudali, Najia, Amane, Ayoub, Rage, Jean-Claude & Tabuce, Rodolphe, 2021, Middle Eocene vertebrate fauna from the Aridal Formation, Sabkha of Gueran, southwestern Morocco, Geodiversitas 43 (5), pp. 121-150 : 129

Carcharhinus sp.

MATERIAL

A dozen isolated teeth, figured material includes FSAC Bouj-345, 346 and 347 .

DESCRIPTION AND REMARKS

Some rare medium-sized sharks ( Fig. 3 G-I) are provisionally attributed to Carcharhinus sp. The upper tooth ( Fig. 4G ) reminds those of Negaprion sp. (unserrated cutting edges, main cusp separated from heels by notches) associated with erect and gracile lower teeth ( Fig. 4H, I ) usually observed in Carcharhinus , and especially in Priabonian species C. frequens (Dames, 1883) . Assignement of middle Eocene carcharhinid teeth to genera Carcharhinus or Negaprion Whitley, 1940 remains debatable and uncertain (see also Sweydan et al. 2019 for discussion) but its attribution to Carcharhinus seemly more appropriate in regard to the dignathic heterodonty. Underwood et al. (2011) only reported a “ Carcharhinidae nov.gen. ” (sic) with smooth cutting edges in the middle Eocene MI, which is easily distinguishable from our material. No other mediumsized carcharhinid was collected within the studied area, particularly no representative of the “bull-shark” group among the Requiem sharks (see Adnet et al. 2007) that displays upper teeth with a modern morphology (e.g., serrated cutting edges). However, such representative was possibly reported in MI by Underwood et al. (2011: Carcharhinus sp. 1) but the rare specimens are often poorly preserved and were provisionally referred to taxa only well-identified in Priabonian levels. Underwood & Gunter (2012) illustrated a large and unique upper tooth probably representing one of the oldest evidences of “Bullshark” from Jamaica ( Underwood & Gunter 2012: fig. 2); postulated to have been from the Yellow Limestone Group exposed at Broomwell and dated as middle Eocene. However, the age of this unique evidence in still uncertain and no other middle Eocene record was verified. Uncertainty about the age of Carcharhinus underwoodi Samonds, Andrianavalona, Wallett, Zalmout & Ward, 2019 , the other oldest representative of “Bull-shark” group, is quite similar; being currently reported from middle to late Eocene of Madagascar. The lack of large modern Carcharhinus species in Boujdour area seems to indicate an early Bartonian age of the deposits, at least their absence is paleoenvironmentally controlled.

Figures

FIG. 3. — Elasmobranchii from Sabkha of Gueran collected around the Archaeocete whale carcasses.(A-F) Tethylamna cf.twiggsensis: A, FSAC Bouj-331 anterior lower tooth in labial view; B, FSAC Bouj-332 anterolateral lower tooth in labial view; C, FSAC Bouj-333 lateral lower tooth in (C1) labial and (C2) lingual views; D, FSAC Bouj-334 posterior lower tooth in labial view; E, FSAC Bouj-335 lateral lower tooth in (E1) labial and (E2) lingual views; F, FSAC Bouj-336 anterior upper tooth in (F1) labial and (F2) lingual views. G-I, Galeocerdo cf. eaglesomei; G, FSAC Bouj-337 anterior tooth in (G1) labial and (G2) lingual views; H, FSAC Bouj- 338 anterolateral tooth in lingual view; I, FSAC Bouj-339 lateral tooth in (I1) labial and (I2) lingual views. Scale bar: 10 mm.

FIG. 4. — Elasmobranchii from Sabkha of Gueran collected around the Archaeocete whale carcasses.A-C, Physogaleus sp.: A, FSAC Bouj-340 anterolateral tooth (A1) labial and (A2) lingual views; B, FSAC Bouj-341 more anterolateral tooth in (B1) labial and (B2) lingual views; C, FSAC Bouj-342 lateral tooth in (C1) labial and (C2) lingual views; D, FSAC Bouj-343 Hemipristis curvatus lateral upper tooth in (D1) labial and (D2) lingual views; E, F, FSAC Bouj-344 Abdounia sp. lateral teeth in labial (E1, F1) and lingual (E2, F2) views; G-I, Cf. Carcharhinus sp.: G, FSAC Bouj-345 lateral upper tooth in (G1) labial and (G2) lingual views; H, FSAC Bouj-346 lateral lower tooth (H1) labial and (H2) lingual views; I, FSAC Bouj-347 anterior lower tooth in (I1) labial and (I2) lingual views. J, Propristis schweinfurthi FSAC Bouj-348 rostral “tooth” in (J1) dorsal and (J2) lateral views. Scale bars: 10 mm.