Abstract

DE IULIIS, Gerardo. On the taxonomic status of Megatherium sundti Philippi, 1893 (Mammalia: Xenarthra: Megatheriidae). Ameghiniana [online]. 2006, vol.43, n.1, pp.161-169. ISSN 1851-8044.

Remains of a medium-sized megathere from Pleistocene deposits near Ulloma, Bolivia, suggest that the commonly accepted synonymy of Megatherium sundti Philippi, 1893 with Megatherium medinae Philippi, 1893 (Mammalia: Xenarthra: Megatheriidae) is unjustified. The strongest evidence supporting the distinction of these species is provided by their femora. In M. medinae the femur is plesiomorphic, bearing nearly parallel lateral and medial margins and an unreduced patellar trochlea. In M. sundti the femur bears strongly concave lateral and medial margins and a somewhat reduced patellar trochlea, resembling the derived condition in Megatherium americanum Cuvier, 1796. Less marked morphological differences in the skull, mandible, and tibia are apparently associated with these distinct femoral morphologies. The differences are clearly sufficient for recognition of M . sundti as a valid species, distinct from M. medinae and another medium-sized megathere, Megatherium tarijense Gervais and Ameghino, 1880, from Pleistocene deposits near Tarija, Bolivia.

Keywords : Mammalia; Megatheriidae; Megatherium sundti; Megatherium medinae; Taxonomy; Pleistocene; Bolivia.