Bythaelurus 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

Bythaelurus sp.

Fig. 5M .

Referred specimen.—BCGM 9074.

Comments.—Unfortunately, comparing this specimen to known scyliorhinid species is difficult because most of the root and the distal crown shoulder are missing. Isolated teeth referred to several scyliorhinid taxa have been reported from the Oligocene of the USA and Europe, including Scyliorhinus dachiardi (Lawley, 1876) (i.e., Baut 1993; Génault 1993; Reinecke et al. 2001), S. distans (Probst, 1879) (i.e., Case 1980), S. aff. coupatezi Herman, 1974 (i.e., Steurbaut and Herman 1978; Reinecke et al. 2001, 2005), and Bythaelurus steurbauti Hovestadt and Hovestadt−Euler, 1995 (see also Reinecke et al. 2005). Early Oligocene records of S. dachiardi were synonymized with Pachyscyllium albigensis Reinecke, Moths, Grant, and Breitkreutz, 2005 , and these teeth differ from our specimen in that the enameloid is smooth and the labial crown foot is nearly flat. In fact, all species of Pachyscyllium Reinecke, Moths, Grant, and Breitkreutz, 2005 have smooth enameloid and straight or only slightly concave labial crown foot. The labial crown foot of S. distans is usually slightly concave and the lingual crown ornamentation is less extensive. Reinecke et al. (2001, 2005) adopted assignment of the “ S. distans ” morphology to Premontreia Cappetta, 1992 (see also Haye et al. 2008).

With respect to crown ornamentation, our specimen, S. aff. coupatezi , and B. steurbauti all bear labial and lingual longitudinal ridges. Steurbaut and Herman (1978) tentatively identified Belgian Oligocene teeth as Scyliorhinus aff. coupatezi because of the close similarity to Pliocene S. coupatezi (see Herman 1975). Hovestadt and Hovestadt−Euler (1995) later concluded that S. coupatezi was related to extant Scyliorhinus but Oligocene S. aff. S. coupatezi was more closely related to Bythaelurus Compagno, 1988 . At 0.7 mm in height, our specimen is much smaller than the type specimens of B. steurbauti (3+ mm in height), but the crown ornamentation is similar. Comparison of our specimen to extant B. canescens Günther, 1878 shows that both species are in the same size range, exhibit similar crown ornamentation, and the labial crown foot is a shelf−like structure that overhangs the root as on lower teeth of B. canescens ( Herman et al. 1990) . For these reasons we assign our specimen to Bythaelurus sp. , but a more specific identification must await the discovery of additional 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.