Catapleura coatesi ( Weems 1988 ), 2014

Robert & Weems, E., 2014, Paleogene chelonians from Maryland and Virginia, PaleoBios 31 (1), pp. 1-32 : 18

Catapleura coatesi ( Weems 1988)

(Figs. 13A–D, 14A–C)

Synonymy — Dollochelys coatesi Weems 1988 , Catapleura repanda (partem) Hirayama 2006

Specimens —CMM-V-4764, second left costal found by Jason Osborn; CMM-V-4767, pygal found by Gary Grimsley; CMM-V-4765, neural found by Mark Bennett.

Locality, horizon, and age — Blue Banks south of Liverpool Point, Charles County, Maryland; “Zone 2” of the Piscataway Member of the Aquia Formation ( Clark and Martin 1901); late Paleocene (early Thanetian) .

Description —Left second costal, thin proximally (3 mm) thickening distally to moderately thin (5 mm), sulcal grooves discernable on dorsal surface. Anterior portion of distal end has sutures for attachment to an anterior peripheral; posterior portion forms the internal border of the anterior internal rim of the costoperipheral fontanelle. Nuchal hexagonal and only about 3 mm thick. Pygal attached to second suprapygal by only a narrow bridge of bone.

Remarks — Weems (1988) described this species and placed it in the genus Dollochelys Zangerl 1971 . Since then, Hirayama (2006) concluded that Dollochelys is a junior synomym of Catapleura . This synonymy is accepted here. However, Hirayama also concluded that the three described species formerly in Dollochelys ( D. casieri Zangerl 1971 , D. atlantica ( Zangerl 1953) and D. coatesi ) are all essentially identical with C. repanda and thus are junior synonyms of that taxon. With this the present author disagrees. Many but not all of the features of D. coatesi are the same as in C. repanda , but a second specimen of C. coatesi illustrated here ( Fig. 14A) indicates by the position of its sulcal grooves that there was only a very narrow vertebral scale as in the type specimen of Catapleura coatesi and quite different from the much wider vertebral scale characteristic of C. repanda . Since no specimen has been found with a vertebral scale width intermediate between these two species, available evidence still clearly favors these being distinctly different species. The fact that C. coatesi is found in the late Paleocene Aquia Formation, while the type material of C. repanda and D. atlantica both come from the early Paleocene Hornerstown Formation, further casts doubt on any likely synonymy of C. coatesi with C. repanda and instead suggests that C. repanda is probably ancestral to C. coatesi .