Rhizoprionodon sp.

Cicimurri, David J. & Knight, James L., 2009, Late Oligocene sharks and rays from the Chandler Bridge Formation, Dorchester County, South Carolina, USA, Acta Palaeontologica Polonica 54 (4), pp. 627-647 : 634

Rhizoprionodon sp.

Fig. 5H .

Referred specimens.—BCGM 9069 and 9070, SC 2009.18.9.

Comments.—These teeth are small (6 mm in total width) and imperfectly preserved, making it difficult to distinguish them from similarly toothed sharks like Sphyrna and even Physogaleus . Teeth of all of these taxa can have highly concave mesial cutting edges, as is the case with our specimens. Our specimens lack cusplets as seen on the distal blade of Physogaleus . Teeth of Sphyrna media Springer, 1940 can have concave mesial edges and convex distal heel, but we identify our specimens as Rhizoprionodon because the mesial edge is very concave, with the cusp being narrower and cusp apex more vertically oriented. Our teeth are similar to Oligocene specimens from North Carolina identified as R. fischeuri ( Müller 1999: pl. 8: 2–4), but a larger sample is needed to accurately determine the identity of these Chandler Bridge teeth.

Figures

Fig. 5. Carcharhiniform sharks from Summerville, upper Chattian. A–D. Carharhinus gibbesi (Woodward, 1889). A. BCGM 9059, juvenile upper anterior tooth, labial view. B. BCGM 9060, adult upper anterior tooth, labial view. C. BCGM 9061, juvenile upper lateral tooth, labial view. D. BCGM 9058, adult lower anterior tooth, labial view. E, F. Physogaleus aduncus (Agassiz, 1835). E. BCGM 9064, upper lateral tooth, labial view. F. BCGM 9066, lower anterior tooth, labial view. G. Physogaleus sp., BCGM 9068, antero−lateral tooth, labial view. H. Rhizoprionodon sp., BCGM 9070, labial view. I, J. Hemipristis serra (Agassiz, 1835). I. BCGM 9073, adult upper lateral tooth, labial view. J. BCGM 9072, juvenile upper lateral tooth, labial view. K. Sphyrna cf. S. media Springer, 1940, BCGM 9077, lateral tooth, labial view. L. Sphyrna zygaena (Linneaus, 1758), BCGM 9079, lateral tooth, lingual view. M. Bythaelurus sp., BCGM 9074, labial view. N–P. Galeorhinus sp. N. BCGM 9081, parasymphyseal tooth, labial view. O. BCGM 9082, antero−lateral tooth, labial view. P. BCGM 9083, lateral tooth, labial view.