Neogene sloths from Bolivia: northwestern South America’s importance in the evolution of Tardigrada

FRANÇOIS, PUJOS; GERARDO, DE IULIIS; BERNARDINO, MAMANI QUISPE

Paris, Francia

Congreso; 8th International Congress of Vertebrate Morphology; 2007

Society of Vertebrate Morphology

    As for most South American mammalian clades, knowledge of xenarthran evolution during the Neogene is based mainly on Argentinian remains, a circumstance related to the history and development of paleontology in this continent. The southern area of South America has generally been considered as the cradle of sloth evolution, and Argentinian taxa as phylogenetically and morphologically central among sloth lineages. Recent discoveries in the Deseadan SALMA Bolivian localities Salla and Lacayani, as well as revision of material from the Laventan SALMA (middle Miocene) of Quebrada Honda, Huayquerian SALMA (late Miocene) of Achiri and Monterhermosan SALMA (early Pliocene) of Ayo Ayo-Vizcachani and Pomata, indicate that this Patagonian model is an oversimplification.     The oldest true Tardigrada is recognized in the Tinguirirican SALMA (early Oligocene) of Chile and the first sloth faunas are present in the Deseadan SALMA levels of Bolivia (Salla) and Argentina (La Flecha). We have identified at least two new Laventan SALMA Hapalops-like forms, several new Huayquerian SALMA Xyophorus specimens, two new peculiar Mylodontidae genera from the Huayquerian and Montehermosan SALMAs, and several indeterminate Montehermosan SALMA Megatherioidea. These new sloths, in addition to the well known Pseudoglyptodon sallaensis (Deseadan SALMA), Xyophorus villarroeli (Huayquerian SALMA), Megatherium altiplanicum (Montehermosan SALMA), and Eremotherium sefvei (Lujanian SALMA), confirm a distinct evolutionary pattern during the Neogene in west-central South America that was probably related to a distinct environment. Bolivian faunas could facilitate the correlation of more southern faunas with tropical faunas, such as the La Venta fauna from the middle Miocene of Colombia.