GLYPTODONTINES (XENARTHRA, GLYPTODONTIDAE) AND THE GREAT AMERICAN BIOTIC INTERCHANGE: A NEW INTERPRETATION.

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

Cleveland, USA

Congreso; SIXTY-EIGHTH ANNUAL MEETING. SOCIETY OF VERTEBRATE PALEONTOLOGY; 2008

SOCIETY OF VERTEBRATE PALEONTOLOGY

Until recently, the earliest records of Glyptodontidae Glyptodontinae (Xenarthra) were limited to late Miocene-Pliocene (“Araucanense”, ~7 Ma) of southern South America (Glyptodontidium tuberifer Cabrera). The entrance of this group of glyptodonts to North America during the Great American Biotic Interchange was interpreted as a unidirectional faunal migration with the subsequent differentiation of a new genus (Glyptotherium), probably in the late Pliocene. A new comparative study of materials from the Mio-Pliocene of northernmost South America (Venezuela and Colombia) and traditionally included within Glyptodontidae Propalaehoplophorinae (Asterostemma spp.), suggests these taxa are not Propalaehoplophorinae but represent the first stages in the cladogenesis of Glyptodontinae Glyptodontidae; they are currently assigned to a recently established genus, Boreostemma. The first records of this clade in southernmost South America coincide with the acme of the “Age of Southern Plains”, which probably extended from Venezuela to Argentinean Patagonia during the late Miocene-Pliocene. These great open extensions of savannah habitat may have favored the dispersal of the glyptodontines into more southern areas through “Andean biogeographical corridors.” The discovery of Glyptotherium sp., cf. G. cylindricum (one of the most derived species of the genus and until recently, limited to the holotype, from central Mexico) in the latest Pleistocene (ca 15-12 ka) of Venezuela supports the bidirectional faunal migration during the GABI, probably associated with a biogeographical “corridor” that formed during one of the later glacial periods. The immigration from North America is a new case of re-entrance of a group that emigrated from South America and diversified in North America, as has already been proposed for other xenarthrans (e.g., Cingulata: Pampatheriidae and Phyllophaga: Megatheriinae). Recent reports that postulate the ingress of glyptodontines to North America ~3.9 Ma, prior to the establishment of the Isthmus of Panama as a continuous land bridge, require new interpretations concerning identification of the emigrant taxa and the derived genera in North America.