Pseudocarcharias undetermined

aff. Pseudocarcharias sp. Fig. 5O–R Material examined UNITED STATES OF AMERICA – Mississippi • 2 isolated teeth; Catahoula Formation; SC 2013.28.269 (Fig. 5O–P), SC 2013.28.270 (Fig. 5Q–R). Description SC 2013.28.269 measures 23 mm in total height and 10 mm in width. It bears a tall and rather erect main cusp. Although the cusp is slightly distally inclined, it has a distinct mesial curvature that is the result of the concave mesial cutting edge intersecting apically with the convex distal cutting edge. Both cutting edges are smooth and sharp, and they extend onto mesial and distal shoulders. The transition from main cusp to lateral shoulder is highly curved but not angular. The shoulders are very low and slightly convex at their distal ends, and the mesial shoulder is longer than the distal one (Fig. 5O). The labial crown face is very weakly convex, but the lingual face is very convex, and both faces are smooth. The root is bilobate with strongly diverging lobes that are thin, elongated, and have a pointed extremity (the distal lobe is damaged). The interlobe area is U-shaped. A thin and shelf-like lingual boss bears a very short nutritive groove (Fig. 5P). SC 2013.28.270 is a smaller tooth measuring 7 mm in total height and 7 mm in width, and having a distally inclined and curved main cusp. The smooth and sharp cutting edges extend onto elongated mesial and distal shoulders. The mesial shoulder is not strongly distinguished from the main cusp, whereas the transition from the distal cutting edge to the distal shoulder is a deeply concave line. The shoulders are low, elongated (slightly longer mesially), and their distal ends are somewhat pointed (Fig. 5Q). The labial crown face is weakly convex, the lingual face is strongly convex, and the enameloid is smooth. The strongly bilobate root bears a very short lingual nutritive groove (Fig. 5S). The root lobes are very highly diverging, relatively short, thin, and have pointed extremities. The interlobe area is V-shaped. Remarks Although different from each other in terms of overall shape, the features shared by SC 2013.28.269 and SC 2013.28.270 lead us to conclude that they represent the same species. Specimen SC 2013.28.269 (Fig. 5O–P) is reminiscent of a more anteriorly located tooth, whereas SC 2013.28.270 (Fig. 5Q–R) is from a lateral jaw position. The smooth cutting edges, curved transition from main cusp to lateral shoulder, and lack of lateral cusplets distinguish these teeth from those of Otodontidae and Carchariidae occurring within the Catahoula Formation. The two specimens described above are perhaps the most enigmatic within the Catahoula Formation fish assemblage. They are differentiated from comparably-sized teeth of Carcharias cuspidatus (see above) by their lack of cusplets and continuous transition from main cusp to lateral shoulders. Specimens SC 2013.28.269 and SC 2013.28.270 are similar to teeth of Mitsukurinidae, two species of which, Mitsukurina lineata (Probst, 1879) and Woellsteinia oligocaena Reinecke et al., 2001, have been reported from Oligocene strata elsewhere (Reinecke et al. 2005). However, the Catahoula Formation teeth lack the longitudinal ridges on the lingual crown face that characterizes those taxa, and instead have smooth crown enameloid. Specimens SC 2013.28.269 and SC 2013.28.270 are very weakly cuspidate (particularly the former specimen) and are comparable to teeth within the jaws of male and female Pseudocarcharias kamoharai (Matsubara, 1936) as shown by Pollerspöck & Straube (2020: fig. 10), and they bear similarities to Pseudocarcharias teeth identified by Cigala Fulgosi (1992) from the Middle Miocene (Serravallian) of Italy. The very weakly cuspidate appearance of the lateral shoulders on the Catahoula Formation specimens contrasts with the condition of teeth of the Early Miocene (Burdigalian) P. rigida (Probst, 1879), which has distinctive lateral cusplets on upper and lower lateral teeth (Bracher & Unger 2007). To our knowledge, Pseudocarcharias does not have a pre-Miocene fossil record (also Cappetta 2012), and the Catahoula Formation teeth would represent a significant temporal range extension back to the “middle” Oligocene. Additional specimens, especially distinctive anterior teeth, are necessary to corroborate the identity of these two teeth.