Physogaleus 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 : 633

Physogaleus sp.

Fig. 5G .

Referred specimens.—BCGM 9067 and 9068, SC 2009.18.8.

Comments.—Our specimens are broken and/or abraded, but the largest specimen would have measured approximately 8 mm in total width. All of our specimens appear to represent antero−lateral jaw positions. The mesial cutting edge is often medially convex but may be slightly sinuous, and it is smooth (some teeth exhibit very weak basal serration). Although the specimen illustrated shows four well differentiated cusplets, the distal heel is generally rather smooth except for one or two poorly differentiated cusplets. Teeth of Oligocene Physogaleus latus (Storms, 1894) are easily distinguished from our specimens in having large serrations on the basal half of the mesial edge (see Baut and Génault 1999; Reinecke et al. 2001, 2005), and individual cusplets on the distal blade are more numerous, much larger, and well differentiated from each other. The teeth of P. maltzani (Winkler, 1875) appear to have a narrower cusp that is also more elongated, the lower part of the mesial cutting edge is more consistently serrated, and the distal blade has three or four well differentiated cusplets ( Reinecke et al. 2005). Teeth of P. singularis (Probst, 1878) also have a virtually smooth mesial cutting edge, but this species differs in having a narrower and more elongated cusp, and concave to weakly sinuous mesial cutting edge. Reinecke and Hoedemakers (2006: 4) suggested the possibility that P. singularis is synonymous with P. latus . Although P. latus reportedly survived at least into the early Miocene ( Reinecke and Hoedemakers 2006), Haye et al. (2008) stated that the taxon was characteristic of the Rupelian, whereas P. maltzani occurs in the early Chattian, and P. singularis occurs in late Chattian to middle Miocene deposits. Miocene P. hemmooriensis Reinecke and Hoedemakers, 2006 differ from Oligocene species in having very narrow, more erect and sinuous cusps. The teeth in our sample appear to represent a new species, but this determination must await the discovery of a larger sample of complete 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.