New Xenarthra Tardigrades of Venezuela, outstanding diversity at low latitudes

CARLINI, A. A., SCILLATO-YANÉ, G. J. Y BRANDONI, D.

La Plata

Jornada; Reunión en Homenaja a Rosendo Pascual, Museo de La Plata; 2005

The new outstanding diversity of tardigrades here reported in Socorro Formation (Middle Miocene), Urumaco Formation (Late Miocene- Early Pliocene?), and Codore Formation (Pliocene) of Northern Venezuela, is reflected by two new genera and three new species of Mylodontoidea, and two new genus and species of Megatheriinae. Three main lineages could be distinguished among the Mylodontoidea: 1) a new gen. ”A”, related to Pseudoprepotherium Hoffstetter 1961; 2) Urumacotherium garciai Bocquentin 1984 of uncertain affinities because of its unique characters; and 3) a new gen. “B”, which is considered a Lestodontinae. We interpret that 1) and 2) could be shows a low latitude diversification of mylodontoids first appears in the Late Oligocene of Patagonia. The new Megatheriidae represent the first Tertiary Megatheriinae of Venezuela, and the second record of the subfamily at low latitudes in South America. The remains are assigned to two new genus and species, one from the Urumaco Formation, and one from the Codore Formation. The anatomical features of the first one suggest that it may be correlated with Chasicoan- Huayquerian megatheriines. The second one is closely related to Eremotherium Spillmann 1948, suggesting that this clade evolved at low areas of middle and low latitudes in northern South America and Central America. Since almost all the recorded species from Venezuela are large, there are two possible interpretations: 1) the ’faunas‘ were composed only of large-sized tardigrades, thus making them unique for the South American Tertiary, and 2) the middle and small sized taxa are absent because of taphonomic bias, thus implying that the faunal diversity was higher than has currently been recovered.