Galeorhinus undetermined

Galeorhinus sp. Fig. 9A–B Material examined UNITED STATES OF AMERICA – Mississippi • 1 isolated tooth; Catahoula Formation; SC 2013.28.114 (Fig. 9A–B). Description SC 2013.28.114 is an incomplete tooth having a crown width measuring 2.5 mm and crown height of approximately 1.2 mm. The mesial edge of each tooth is smooth, elongated, and convex basally but otherwise straight. This edge is strongly inclined distally, and a smooth cutting edge is only obvious along its lower one-half. The distal cutting edge is short and lingually inclined, and it intersects apically with the mesial margin to form a small distally inclined cusp. A short, oblique distal heel bears a series of three denticles that decrease in size basally (Fig. 9B). The labial face is weakly convex and appears to have been thickened at the base (Fig. 9A). The lingual face is more strongly convex. Crown ornamentation is not obvious, but the specimen is ablated. The root is not preserved. Remarks We tentatively identify specimen SC 2013.28.114 (Fig. 9A–B) as Galeorhinus due to its small size and apparently thickened labial crown foot (Fig. 9A). The tooth differs from superficially similar teeth of Sphyrnidae (see below) and other Carcharhinidae from the Jones Branch locality by having a high and oblique distal heel that bears numerous well-defined denticles. It also differs from Carcharhinus elongatus and Physogaleus spp. by being unserrated and lacking denticles on the mesial cutting edge. Additionally, the labial crown foot of Carcharhinus spp. and Physogaleus spp. is flat and not thickened to overhang the root. The unserrated cutting edges easily separate the two teeth from those of Galeocerdo (see below). Ebersole et al. (2019) identified three Eocene Galeorhinus species from Gulf Coastal Plain deposits in Alabama, namely Galeorhinus aff. G. duchaussoisi Adnet & Cappetta, 2008, G. louisi Adnet & Cappetta, 2008, and G. ypresiensis (Casier, 1946). However, none of these species are known to persist into the Oligocene (Adnet & Cappetta 2008). The Catahoula Formation specimens are similar to a lateral tooth identified by Cicimurri & Knight (2009) from the Chattian Chandler Bridge Formation of South Carolina, and Müller (1999) noted a specimen from the Rupelian Old Church Formation of Virginia that is comparable to SC 2013.28.114. Reinecke et al. (2005) and Haye et al. (2008) documented several Oligocene Galeorhinus sp. from the late Oligocene (late Chattian) of Germany, and the Catahoula Formation material differs from some of those specimens by the lack of labial ornamentation (Reinecke et al. 2005). Unfortunately, the poor preservation of the singular Catahoula Formation specimen available to us inhibits our ability to effectively identify the taxon to species.