Chapter 12. An Introduction to Cingulate Evolution and their evolutionary history during the Great American Biotic Interchange: Biogeographical clues from Venezuela.

CARLINI A.A.; ZURITA AE.

Urumaco and Venezuela Paleontology. The Fossil Reccord of the Northern Neotropics, Sanchez-Villagra M., Aguilera O. and Carlini A.A. (eds).

INDIANA UNIVERSITY PRESS

Lugar: Bloomington; Año: 2010; p. 233 - 255

The Xenarthra are a peculiar group of mammals, with a long and successful evolutionary history that took place in America during most of the Cenozoic, from the Early Paleocene to the present (Scillato-Yané 1986; Carlini et al. 2005; Hill 2006). Their current diversity (about 13 genera with some 31 species) does not reflect the remarkable diversity that they reached in the past, with more than 160 genera (see McKenna and Bell 1997; Hoffstetter 1958; Paula Couto 1979) that probably included more than 400 species. The origin of this clade was quite probably in America, although fossil forms have also been found in Eocene sediments of Antarctica, from the time when the latter continent was connected to southern South America, during the Early Cenozoic (Carlini et al. 1990; Vizcaíno and Scillato-Yané 1995). In addition, in 1981 Eurotamandua was described for the European Eocene as a Vermilingua (Storch 1981), although the affinities of this species are a matter of controversy (Szalay and Schrenck 1998; Rose et al. 2005), and today it is not considered as a xenarthran. The living Xenarthra includes sloths, anteaters, and armadillos. This clade has played a special role in the discussions about the common ancestor of placental mammals, given that xenarthrans are frequently interpreted as a basal group in the radiation of placentals. According to some estimates made on the basis of molecular clocks, the divergence of xenarthrans from other placentals could have taken place during the Early Cretaceous (Springer and Murphy 2007). However, the paleontological evidence does not support this estimate (Asher et al. 2005; Wible et al. 2007).