Preliminary observations of a new Pleistocene Megatherium (Mammalia: Xenarthra: Megatheriidae) from the peruvian coast

FRANÇOIS, PUJOS; RODOLFO, SALAS

Diamante, Argentina

Congreso; Reunión Anual de la Asociación Paleontológica Argentina; 2002

Asociación Paleontológica Argentina

    A Quaternary mammal fauna was discovered in the desert area of Sacaco and Aguada de Lomas. A small megatheriine specimen (Megatherium sp. nov.), represented by various elements of the limbs and a part of the tail, was found in the “Sacaco-2” site, in association with Equiidae, Gomphotheriidae and Cricetiidae. This is the first record of a Ground Sloth from the Pleistocene of the southern Peruvian coast. As is the case in all others Megatherium species, the hand of this new Peruvian taxon shows four functional digits and a carpal-metacarpal complex (MCC), the latter being constituted of the first digit and the trapezium. This new taxon is close to M. elenense (southern Ecuador, northern Peru), M. tarijense (Bolivia) and M. medinae (Chile) but clearly distinct of all of them. The main characters are, among others, a particular and extremely reduced MCC, the undifferentiated Mc III-IV-V facets of the unciform, absence of fusion of the distal epiphysis of the tibia and the fibula, the extremely lateral position of the navicular facet of the astragalus, two original articulations on the ectocuneiform for the mesocuneiform-entocuneiform-complex and the Mt IV. M. americanum is probably the most derived Megatherium species and several characters allow to suggest than M. tarijense is relatively most specialized than Megatherium sp. nov.. The sedimentological, petrographical and micropaleontological analyses of Sacaco and Aguada de Lomas area, show the existence of a warm and humid littoral and coastal environments of fresh waters, which contrasts with the climate of nowadays.