CARCHARHINIFORMES COMPAGNO, 1973

Cicimurri, David J. & Knight, James L., 2019, Late Eocene (Priabonian) elasmobranchs from the Dry Branch Formation (Barnwell Group) of Aiken County, South Carolina, USA, PaleoBios 36, pp. 1-31 : 7-9

CARCHARHINIFORMES COMPAGNO, 1973 GALEOCERDIDAE HERMAN AND VAN DEN EECKHAUT, 2010 GENUS GALEOCERDO MÜLLER AND HENLE, 1837 GALEOCERDO SP.

( FIG. 3E, F )

Referred specimens —SC96.97.11, three incomplete teeth; SC 2001.1.8, incomplete anterior tooth; SC 2001.1.9, lateral tooth; SC 2001.1.10, three partial teeth; SC2013.38.16, anterolateral tooth ( Fig. 3E, F ); SC2013.38.17, incomplete lateral tooth; SC2013.38.18, incomplete tooth; SC2013.38.19, four incomplete teeth.

Remarks —All 15 specimens lack enameloid but they are morphologically consistent with Galeocerdo , having an elongated and broadly convex mesial edge, short distal edge that forms a triangular cusp with the mesial edge, and elongate, serrated distal heel. In terms of gross morphology, the Dry Branch Formation specimens differ from Eocene Galeocerdo eaglesomei White, 1926 in having a lower and more uniformly convex mesial cutting edge, as opposed to a rather high and conspicuously convex apical portion to the mesial edge. We believe that the Dry Branch Formation Galeocerdo teeth are comparable to specimens from the Clinchfield Formation of Georgia identified as Ga. alabamensis Leriche, 1942 by Parmley and Cicimurri (2003). However, the specific identification made by those authors appears to be in error, as examination of Leriche’s (1942) alabamensis holotype leads us to conclude that it is actually Physogaleus Cappetta, 1980 . The assignment of the Clichfield material to Ga. alabamensis by Parmley and Cicimurri (2003) was based on White’s (1956) identification of specimens from South Carolina as Ga. alabamensis , which are not conspecific with Leriche’s (1942) taxon.

In addition to Alabama (White 1956, Thurmond and Jones 1981), Ga. alabamensis was also documented from Arkansas (Westgate 1984) and Louisiana (Manning and Standhardt 1986). Another species, Ga. clarkensis , was founded by White (1956) based on a small number of teeth from the late middle Eocene of Alabama, but Manning and Standhardt (1986) synonymized this taxon with Ga. alabamensis , considering the former to represent upper teeth and the latter lower teeth in the same dentition. However, as noted above, the “ Galeocerdo ” alabamensis morphology is more appropriately identified as Physogaleus . In Georgia, Case (1981) identified Ga. clarkensis from the Clinchfield and Dry Branch (Twiggs Clay Member) Formations, but Case and Borodin (2000) later reported Ga. latidens Agassiz, 1843 from the Dry Branch Formation (Irwinton Sand Member). It is apparent that Eocene records of Galeocerdo from North America are in further need of evaluation.

Our examination of Ga. clarkensis teeth from the middle Eocene (Bartonian) Gosport Sand (Claiborne Group) of Alabama, housed at MSC, showed that the mesial cutting edge bears coarse, compound serrations (largest serrations bear smaller serrations). Additionally, examination of Ga. eaglesomei teeth from the middle Eocene (Lutetian) Lisbon Formation (Claiborne Group) of Alabama, also at MSC, revealed that serration on the mesial edge is simple (large serrations do not bear smaller serrations). As our specimens are incompletely preserved, we cannot determine the precise shape of the original crown or if the serrations were simple or compound (serrations on serrations), and we refrain from making a specific identification.

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.