Alopias undetermined

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

ALOPIAS SP.

( FIG. 2P–S )

Referredspecimens —SC2001.1.65,tooth;SC2001.1.66,

tooth.

Remarks —Specimens bear a broadly triangular, distally curving crown. Unfortunately, the enameloid is lacking due to taphonomic processes, and the dentine cores are exposed. There is no indication that lateral cusplets were present on SC2001.1.65 ( Fig. 2P, Q ), but dentine cores of what appear to be two mesial basal cusplets and an incipient distal cusplet are visible on SC2001.1.66 ( Fig. 2R, S ). Unfortunately, the enameloid on the two specimens is imperfectly preserved, and the shape of the crown may not be accurately reflected. Coupled with the very limited sample size (n=2), we could therefore not effectively compare the Dry Branch Alopias teeth to those of any of the several Eocene species that have been described, which include Al. crochardi Ward, 1978 , Al. leeensis Ward, 1978 , Al. denticulatus Cappetta, 1981 , and Al. alabamensis White, 1956 . The crown foot of both Dry Branch Formation teeth is very convex and obviously overhangs the root ( Fig. 2Q, S ), and the lingual side of the root is bisected by a shallow nutritive groove ( Fig. 2P, R ). These features are consistent with teeth of Al. crochardi and Al. denticulatus , but our specimens appear to have lacked cusplets like those seen on Al. denticulatus . Teeth of Al. leeensis and A. alabamensis lack nutritive grooves and crowns appear much wider than seen on the Dry Branch Formation specimens. Our two specimens are similar to teeth we observed within the jaws of Al. superciliosus (Lowe, 1841) housed at SC, and perhaps the Dry Branch Formation taxon is related to this “group” (sensu Cappetta, 2012). A larger and better preserved sample is needed for a more specific determination.

Figures

Figure 2. Shark teeth from the Dry Branch Formation (Priabonian) of Aiken County, South Carolina. A–D. Notorynchus sp. cf. No. kempi teeth. Lower left tooth in lingual (A) and labial (B) views, SC2013.38.1. Lower right tooth in labial (C) and lingual (D) views, SC96.97.4. E. Squatina sp. cf. Sq. prima. Antero-lateral tooth in labial view, SC96.97.9. F,G. Nebrius sp. cf. Neb. thielensi. Anterolateral tooth in labial (F) and occlusal (G) views, SC2013.38.5. Labial at top in G. H. Ginglymostomatidae. Tooth in labial view, SC2013.38.7. I–O. Carcharias sp. Third lower right anterior tooth in labial (I) view, SC2001.1.55. Third upper right anterior tooth in lingual (J) and labial (K) views, SC2001.1.57. First lower right anterior tooth in labial (L) view, SC2001.1.59. Second lower right anterior tooth in labial (M) view, SC96.97.44.1. Second upper right anterior tooth in lingual (N) view, SC96.97.42. Lower left lateral tooth in lingual (O) view, SC96.97.43. P–S. Alopias sp. Tooth in labial (P) and lingual (Q) views, SC2001.1.65. Tooth in labial (R) and lingual (S) views, SC2001.1.66. Scale bars=1 cm in A–D, I–K, N, O; 5 mm in E–G, L–M, P–S; 1 mm in H.