Mobula, Rafinesque, 1810

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 : 639-640

Mobula cf. M. loupianensis Cappetta, 1970

Fig. 9.

Referred specimens.—BCGM 9133–9142, SC 2009.18.20.

Comments.—A variety of morphotypes are represented in our sample, and Notabartolo di Sciara (1987) reported that extant species of Mobula Rafinesque, 1810 can exhibit monognathic, dignathic, gynandric, and ontogenetic heterodonty. We regard the varied morphotypes in our sample to represent heterodonty within a single species. Purdy et al. (2001) described a number of Mobula tooth morphologies that were collected from the Miocene Pungo River Formation, and these teeth are quite similar to M. loupianensis reported from the middle Miocene of France ( Cappetta 1970: 108–110, fig. 20). Regarding the specimens Cappetta (1970) illustrated, those in fig. 20A–D appear to be male teeth, whereas fig. 20F may represent a female. In Fig. 9, the teeth shown in A–D are equivalent to teeth illustrated by Cappetta (1970) in his fig. 20E, D, F, and B, respectively. Based on the work of Notabartolo di Sciara (1987), we believe that M. pectinata Cappetta, 1970 could be conspecific with M. loupianensis (see Fig. 9E).

The Chandler Bridge Mobula teeth differ from those of the extant species M. eregoodootenkee (Bleeker, 1859) , M. thurstoni Lloyd, 1908 , and M. tarapacana (Philippi, 1893) in that the occlusal surface is smooth, and teeth of M. japonica (Müller and Henle, 1841) are similar to those of Manta Bancroft, 1829 (see Notabartolo di Sciara 1987). Our sample contains morphologies attributed to M. loupianensis and M. pectinata , as well as to other Oligocene teeth identified as M. irenae Pfeil, 1981 . The validity of these species is questionable because all are based on relatively few specimens (i.e., 15, 4, and 13 teeth, respectively), and the original reports provided no clear indication of morphological variation within each species. Mobula pectinata , M. irenae , and M. loupianensis exhibit some very close morphological similarities, and we consider it entirely possible that all of these represent heterodonty (monognathic, dignathic, ontogenetic, and gynantric) within the same taxon.

Manta melanyae Case, 1980 was described from the Trent Marl of North Carolina. However, of the two teeth originally illustrated, one specimen is referable to Mobula ( Case 1980: pl. 10: 1a–e) and the other may be Paramobula Pfiel, 1981 (see Case 1980: pl. 10: 2a–e). The former specimen does not differ appreciably from our Mobula sample, and morphologies illustrated by Müller (1999: pl. 15: 1–3) from the Old Church Formation also fall within the range of variation we observed. We consider Manta melanyae to be a nomen dubium, and Oligocene Mobula from the Atlantic Coastal Plain may be conspecific.

Stratigraphic and geographic range.—?Oligocene (Chattian), USA (North and South Carolina); Miocene, France.