A new glyptodontinae (Xenarthra, Glyptodontidae) from northern South America: its implications in the Great American Biotic Interchange

ZURITA, AE; CARLINI A.A.; GILLETTE D.

Pittsburg

Congreso; 70th Anniversary Meeting Society of Vertebrate Paleontology; 2010

The population dynamics of the Glyptodontinae (Glyptodontidae) during the Great American Biotic Interchange (GABI) has been reinterpreted as a bidirectional process, with the reentry of some North American taxa in the latest Pleistocene into Venezuela. The first records of Glyptodontinae in North America are cf. Glyptotherium from the Pliocene of north-central Mexico. A new Glyptodontinae from the late Pliocene of northern Venezuela (San Gregorio Formation), prior the GABI, presents significant paleobiogeographical and phylogenetic implications. The material is represented by numerous osteoderms of the dorsal carapace. From a morphological perspective a comparison with the North American taxa (Pliocene-Late Pleistocene; Glyptotherium spp.) and with the southern South American taxa (Late Miocene- Early Holocene; Glyptodontidium tuberifer, Paraglyptodon chapalmalensis, P. uquiensis, and Glyptodon), reveals a closer relationship with Glyptotherium than to the southern South American forms. Some of these characters could be interpreted as primitive for the Glyptodontines. Shared characters include: 1) the sulci that delimit the central figure are shallower and narrower than observed in the southern South American taxa; 2) the dorso-ventral diameter of the osteoderms is less than in Paraglyptodon, Glyptodontidium and Glyptodon; 3) the exposed surface of the osteoderms is clearly rough and punctate; and 4) the central figure in the exposed surface is bigger. The available evidence suggests: 1) that this new late Pliocene Glyptodontine from northern South America is closely related to those that participated in the GABI and the ancestry of Glyptotherium; 2) in turn, that the southern South American taxa, especially the Miocene and Pliocene ones (i.e., G. tuberifer and Paraglyptodon) are clearly more closely related to the Pleistocene genus Glyptodon; and 3) finally, it is possible that the northern (Boreostemma spp. and the new Glyptodontinae presented here) and southern taxa (Glyptodontidium, Paraglyptodon and Glyptodon) of South America represent distinct lineages, separated from, at least, the Late Miocene-early Pliocene.