Análisis tafonomico de los macromamíferos del Mioceno superior de Caleufú (La Pampa, Argentina)

Abstract

The taphonomic results on the fossil macromammal assemblage from Caleufú (La Pampa Province, Argentina) are presented. The fossiliferous level corresponds to the Cerro Azul Formation, Late Miocene in age. Among the different outcrops of this formation, Caleufú presents the greatest concentration of fossils, with a density of 4,1 remains/m2. Most fossils were recovered on surface over an area of 1590 m2. Identifyed remains (3200) include reptiles, undetermined birds, and many mammals. Macromammals are represented by a minimal number of individuals of 26 and at least 17 taxa, showing a high diversity, detaching that 11 of these taxa are Xenarthra. Most mammal remains are very fragmented and broken, and just 13 basipodial elements are complete. Only two hemimandibles, a maxillary fragment and a few isolated teeth are well preserved. Indeterminable studied fragments (638) are relatively small sized, and cubic morphologies predominate. Most specimens show a high degree of weathering. The observed taphonomic attributes can be explained by a long exposition to environmental factors before the burial process. However, some bones show lichen corrosion, which would indicate moments of reexposition. Abrasion is scarcely present and only on some mineralized bones with sediment infilling. The taphonomic analysis concludes that specimens resulted from accumulation of skeletal elements from different animals that died in the area during a long period of time, corresponding to the time of developing soil. Diversity would be the result of condensation of remains coming from succesive autochtonous comunities