CARCHARHINIDAE

Cicimurri, David J. & Knight, James L., 2022, Late Eocene (Priabonian) elasmobranchs from the Dry Branch Formation (Barnwell Group) of Aiken County, South Carolina, USA, PaleoBios 36, pp. 1-31 : 13-14

CARCHARHINIDAE GENUS INDETERMINATE

( FIG. 4A–D )

Referred specimens —SC2013.38.104, tooth; SC2013.38.105,tooth;SC2013.38.106,tooth;SC2013.38.107, tooth; SC2013.38.108, tooth; SC2013.38.109, three teeth.

Remarks —Unfortunately, the eight teeth lack enameloid. However, they are distinguished by the presence of a single pair of cusplets that mark the base of the main cusp and beginning of short enameloid shoulders ( Fig. 4A, C ). These teeth are superficially similar to Abdounia enniskilleni , but whereas the cusplets of Ab. enniskilleni form the mesial and distal ends of the crown, cusplets of Carcharhinidae indet. are comparatively smaller and located near the middle of the crown (compare Fig. 3H, I to Fig. 4A, C ). Some of the specimens are very similar to White’s (1926) Hypoprion overricus (reassigned to Abdounia overrica by Cappetta 2006), but the teeth in the Dry Branch sample differ in that cusplets appear to have been smaller. The Dry Branch teeth also bear similarities to Case’s (1980) Negaprion furmiskyi ( Cappetta [2006] considers this species to belong within Abdounia ), but a significant difference between the two morphologies is that the diminutive cusplets occur at the ends of the lateral shoulders on Ab. furimskyi , whereas they are between the end of the shoulder and the base of the cusp of the Dry Branch teeth.

Comparison of the Dry Branch material to some of the late Eocene teeth identified by Case and Cappetta (1990) as Carcharhinus frequens (pl. 5, figs. 100–103, 106–107; pl. 7, figs. 143–144, 146–148, 151–159) revealed striking similarities. Case and Cappetta’s (1990) assignment of the Egyptian material to Carcharhinus frequens is in error because the teeth differ from most of the specimens illustrated by Dames (1883: pl. 3, fig. 7), which clearly possess a broader, lower cusp and exhibit serrated lateral shoulders. The frequens morphology was considered to be a species of Negaprion by Underwood et al. (2011), and they concluded that the sample examined by Case and Cappetta (1990) contained teeth of Negaprion and an undescribed species of Abdounia .

Figures

Figure 3. Carcharhiniform shark teeth the Dry Branch Formation (Priabonian) of Aiken County, South Carolina. A–D. Physogaleus sp. cf. Ph. latus. Upper left lateral tooth in lingual (A) and labial (B) views, SC2013.38.65. Lower left anterior tooth in labial (C) and lingual (D) views, SC96.97.26. E, F. Galeocerdo sp. Anterolateral tooth in lingual (E) and labial (F) views, SC2013.38.16. G–I. Abdounia sp. cf. Ab. enniskilleni. Anterior tooth in lingual (G) and labial (H) views, SC96.97.30. Lateral tooth in lingual (I) view, SC96.97.31. J–L. Rhizoprionodon?ganntourensis. Anterolateral tooth in labial (J) and lingual (K) views, SC2013.38.98. Lateral tooth in lingual view (L), SC2013.38.99. M–P. Hemipristis sp. cf. He. curvatus. Upper left lateral tooth in lingual (M) and labial (N) views, SC2001.1.21. Lower right anterior tooth in lingual (O) and labial (P) views, SC2013.28.35. Q, R. Negaprion gilmorei. Upper right anterior tooth in lingual (Q) view, SC2013.38.61. Lower right anterolateral tooth in lingual (R) view, SC2013.38.64. Scale bars=1 cm in A–F, M–N, Q–R; 5 mm in G–L, O–P.

Figure 4. Carcharhiniform shark teeth from the Dry Branch Formation (Priabonian) of Aiken County, South Carolina. A–D. Carcharhinidae indeterminate. Anterolateral tooth in labial (A) and lingual (B) views, SC2013.38.105. Anterolateral tooth in labial (C) and lingual (D) views, SC2001.1.43. Labial at right in C. E–P. Isogomphodon aikenensis n. sp. Upper anterior tooth in lingual view (E), SC2013.38.110 (Holotype). Lower lateral tooth in labial (F) and lingual (G) views, SC2013.38.123.1. Lower anterior tooth in labial (H) and lingual (I) views, SC2013.38.119 (Paratype). Upper lateral tooth in labial (J) and lingual (K) views, SC2013.38.112 (Para- type). Posterolateral tooth in labial (L) and lingual (M) views, SC2013.38.114. Posterior tooth in labial (N) and lingual (O) views, SC2013.38.115 (Paratype). Upper anterolateral tooth in lingual (P) view, SC2013.38.111 (Paratype). Scale bars=1 cm in A–D; 5 mm in E–P.