How many Pleistocene species of Lestodon (Mammalia, Xenarthra, Tardigrada)?

Abstract

Among the Tardigrada (Mammalia, Xenarthra), terrestrial sloths were very abundant in the South American fauna during the Cenozoic and were especially well represented in the Lujanian (late Pleistocene–early Holocene) fauna. The last systematic revision of the Pleistocene genus Lestodon from Argentina, Bolivia and Uruguay recognized two species: L. armatus Gervais, 1855 and L. australis Kraglievich, 1934. In this paper we revise the species of Lestodon and assess the possibility of sexual dimorphism in body size. The results obtained from a morphological study and morphometrical analysis of the skull do not support a distinction between the two species. Estimations of body mass based on tibial measurements did not support the case for size sexual dimorphism in Lestodon. Nor can this be observed in cranial dimensions. Consequently, it is proposed that the only valid species of the genus is L. armatus, the type species. We provide an emended diagnosis for L. armatus taking into account features found in specimens previously assigned to L. australis. Although the largest specimens of the genus Lestodon are from the current territory of Argentina, the average size of specimens from Uruguay is marginally larger.

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Keywords:

• megafauna
• late Pleistocene
• palaeobiology
• morphometrics