Paramobula fragilis

Paramobula fragilis (Cappetta, 1970) Fig. 21E–N Mantra fragilis Cappetta, 1970: 112–113. Material examined UNITED STATES OF AMERICA – Mississippi • 2 isolated teeth; Catahoula Formation; MMNS VP-8429 (Fig. 21E–I), MMNS VP-11678 (Fig. 21J–N). Description The crown is wider than long and labio-lingually thin. MMNS VP-8429 measures 4.2 mm in mesio-distal width and 2.2 mm in total apico-basal height, whereas MMNS VP-11678 is 3.5 mm and 3 mm in these dimensions. The labial and lingual faces are lingually inclined and heavily ornamented with longitudinal ridges. These ridges may be wide and widely separated, or thin and closely spaced, or some combination of both (compare Fig. 21E to J). The ornamentation on the lingual face (Fig. 21G, L) is somewhat less extensive than that on the labial face. The labial crown foot of MMNS VP-11687 is somewhat ridge-like and the lingual crown foot is formed into a shelf-like projection. The crown base of MMNS VP-8429 is formed into a robust cingulum that extends around the entire perimeter. The complex occlusal surface is flat to weakly depressed and has very irregular labial and lingual margins (Fig. 21F, K). Additionally, in profile view, the occlusal surface is lingually inclined and rather straight (Fig. 21I). The root is high but labio-lingually thin, and it is located close to the lingual crown margin (Fig. 21N). The basal surface is subdivided into four or five thin lamellae by wide and shallow nutritive grooves (Fig. 21H, M). Remarks These two teeth clearly differ from that of Plinthicus sp. (see above) by the much coarser labial and lingual ornamentation and by the flat occlusal surface that has a highly irregular outline. In contrast, the Plinthicus sp. tooth in our sample (SC 2013.28.522) has a distinctively concave occlusal surface. Specimens MMNS VP-8429 and MMNS VP-11678 are comparable to teeth that Cicimurri & Knight (2009) identified as Paramobula fragilis (Cappetta, 1970) from the Chandler Bridge Formation of South Carolina. Comparison of the Catahoula Formation teeth to a small sample from the Chandler Bridge Formation (SC 2005.2) indicates that the material is conspecific. The taxon Manta fragilis was named by Cappetta (1970) based on teeth from the Middle Miocene (Langhian) of France (Cappetta 1970: pl. 28 fig. 10) that have a high, labio-lingually narrow crown that bears significant vertical ridges on the labial and lingual faces. Pfeil (1981) later erected the name Paramobula for this morphology, but Cappetta & Stringer (2002) and Cappetta (2012) synonymized the genus with Mobula. However, the fragilis morphology is significantly different from teeth of extant Mobula species (see Notabartolo di Sciara 1987) and fossil species like M. loupianensis Cappetta, 1970. We therefore resurrect Paramobula Pfeil, 1981 to accommodate the more Plinthicus -like nature of the fragilis morphotype.