Rhizoprionodon, GANNTOURENSIS, WHITLEY, 1929

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 : 10

RHIZOPRIONODON ? GANNTOURENSIS ( ARAMBOURG, 1952)

( FIG. 3J–L )

Referred specimens —SC96.97.2, four teeth; SC 2001.1.18, tooth; SC 2001.1.19, 40 teeth;SC2013.38.98, anterior tooth ( Fig. 3J, K );SC2013.38.99, lateral tooth ( Fig. 3L ); SC2013.38.100, 18 teeth; SC2013.38.101, 32 teeth; SC2013.38.102, eight posterior teeth; SC2013.38.103, eight distal lateral teeth.

Remarks —One hundred thirteen Dry Branch Formation teeth are similar to those of extant Rhizoprionodon , and to Eocene Rhiz. ganntourensis, in particular. The distal heel of Rhizoprionodon , including Rhiz. ganntourensis, is generally cuspidate ( Arambourg 1952, Herman et al. 1991, Case et al. 1996, Noubhani and Cappetta 1997, Mustafa et al. 2005), but our specimens lack enameloid and this feature is not preserved. However, we examined a tooth of Rhiz. sp. cf. Rhiz. ganntourensis that was recovered by Zullo and Kite (1985) from the Griffins Landing Sand (see Appendix 1), and found that it is very similar to the material listed above. The well preserved Griffins Landing Sand tooth exhibits a cuspidate distal heel, but the translucent enameloid allows us to view the unifromly convex dentine core of the heel, as can be seen on the specimens in our sample.

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.