The cingulates (Xenarthra) of Leisey Shell Pit 1A (Irvingtonian), Hillsborough County Florida

Abstract

The late early Irvingtonian Leisey Shell Pit local fauna provides a superb record of the diversity of shelled edentates in the southeastern United States during the early Pleistocene. Among the four species of cingulates recognized in the Leisey Shell Pit local fauna, two, the dasypodid, Dasypus bellus, and the pampathere, Holmesina floridanus, are well represented in other Pleistocene fossil localities in Florida. Fossil material of D. bellus and H. floridanus, chiefly osteoderms at Leisey 1A, is indistinguishable from comparable material at other Irvingtonian Florida localities except for modest differences in average size. A third cingulate, a large glyptodont, is represented by a small sample of osteoderms, and is tentatively referred to Glyptotherium arizonae. The most notable cingulate in the Leisey Shell Pit local fauna is the thick-armored and relatively large dasypodoid Pachyarmatherium leiseyi, here described as a new genus and species. P. leiseyi is presently known from isolated osteoderms and postcranial elements, and from a nearly complete postcranial skeleton in a private collection currently unavailable for detailed inspection. Large samples of Pachyarmatherium leiseyi osteoderms have been recovered from Leisey 1A and Haile 16A and several isolated postcranial elements from Haile 16A. This new taxon is readily distinguished from other fossil and living armadillos by characteristics of the carapace, including the thickness and morphology of the carapacial osteoderms, a single, narrow transverse zone of imbrication between the pelvic and scapular bucklers and its unique border and caudal osteoderms. It is distinguished from glyptodonts by its clawed ungual phalanges, free dorsal vertebrae, and diminutive and probable edentulous jaws. The aggregate of skeletal morphology suggests that P. leiseyi, was a strong, non-fossorial scratch digger and may have been mymercophagus. Although the detailed phylogenetic relationships of P. leiseyi are uncertain based upon limited available information, it appears to retain many primitive features of cingulates in its postcranial skeleton and is most closely related to the dasypodoid group. P. leiseyi first appeared in the late Blancan in North America, with records from both Florida and South Carolina, and is best known from seven early Irvingtonian localities in peninsular Florida.