Chapter 7. MIDDLE EOCENE-EARLY MIOCENE DASYPODIDAE (XENARTHRA) OF SOUTHERN SOUTH AMERICA, SUCCESSIVE FAUNAS IN GRAN BARRANCA; BIOSTRATIGRAPHY AND PALAEOECOLOGY

CARLINI, ALFREDO A.; CIANCIO, MARTÍN R.; SCILLATO-YANÉ, G. J.

The Paleontology of Gran Barranca: Evolution and Environmental Change through the Middle Cenozoic of Patagonia

Cambridge University Press

Lugar: Cambridge, UK; Año: 2010; p. 106 - 129

ABSTRACTMost biostratigraphic sequences in Patagonia and elsewhere in South Americahave been based on the evolutionary stage and taxonomic representation of “ungulates”(archaic endemic herbivores or southern ungulates) and/or marsupials. Recent collectionsof microfossils made at Gran Barranca, Patagonia, allow us to critically assess the valueof Cingulata (mainly the Dasypodidae) and cingulate assemblages in mammalianbiostratigraphy. The numerous and rich fossil localities and levels at Gran Barrancaprovide the most stratigraphically complete sampling of Cingulata available anywhere inSouth America. Starting with the “Barrancan” (Eocene) level at the base of the sequenceand ending with the “Pansantacrucian” (Miocene) beds at the top of the SarmientoFormation, dasypodid assemblages demonstrate a very close relationship with sea-surfacetemperature variation through the late Paleogene. We have studied 7 successive faunaswith a very rich dasypodid record. While the astegotheriine Dasypodinae decrease indiversity through the late Paleocene-Late Eocene interval, the stegotheriine Dasypodinae,and especially the Euphractinae, increase in diversity through the middle Eocene and intothe early Oligocene, until euphractines became dominant in the late Eocene. Cingulateassemblages permit speculation that between the upper Casamayoran (Cifelli´s“Barrancan”, around 39-41.6 Ma) and the typical Mustersan (about 38.7 to 37.0 Ma) adistinct faunal assemblage may represent a new subdivision of the mammalian sequencein Patagonia.