The value of Cingulata in South American Paleogene Biostratígraphy.

CARLINI, A. A.; CIANCIO, M. R.; SCILLATO-YANÉ, G. J.; R. H. MADDEN

Rio de Janeiro, RJ, Brasil

Congreso; II Congreso Latinoamericano de Paleontología de Vertebrados; 2005

Heretofore, most biostratigraphic sequences have been proposed or substantiated on the basis of southern ungulate and/or marsupial evolutionary stage and diversity. Recent large samples of microfossils collected in Patagonia, Argentina, permit an evaluation of the value of cingulate assemblages for biostratigraphy. The Sarmiento Formation at Gran Barranca yields uniquely complete stratigraphic sampling of Cingulata, starting from Cifelli´s "Barrancan" at the base up to a Pansatacrucian level at the top of the composite section. Throughout this sequence, the composition of cingulates assemblages appears to respond with expectations based on temperature trends as estimates by the Southern Ocean d18O record. On the Eocene, whilw the Dasypodinae Astegotheriini decrease in diversity (while temperatures decresing), the Dasypodinae Stegotheriini and Euphractinae appear and become dominant and diverse. Among "glyptodontoids", diferent lineages are represented by very primitive patterns of surface sculpture, but these lineages become reduced dramatically after the Eocene-Oligocene Transition, givin rise to new lineages that were dominants during the rest of the Paleogene. The cingulate record indicates that between "Barrancan" and Mustersan levels there occurs a distinct new faunal assemblage intermediate in composition that may represent a new Subage. Elsewhere in Patagonia, we recognize another new intermediate Paleogene assemblage in the basal part of Sarmiento Fm. that is more primitive than Cifelli´s "Vacan" but more advanced than the Riochican. Durin this interval of the Paleogene (Riochican-Vacan) marine temperatures increase as does diversity among Dasypodidae.