The pes of Pyramiodontherium bergi (Moreno & Mercerat, 1891) (Mammalia, Xenarthra, Phyllophaga): the most complete pes of a Tertiary Megatheriinae

BRANDONI, D.; CARLINI, A. A.; PUJOS, F.; SCILLATO-YANÉ, G.J.

GEODIVERSITAS

PUBLICATIONS SCIENTIFIQUES DU MUSEUM

Lugar: Paris; Año: 2004 vol. 26 p. 643 - 659

1280-9659

The aim of this paper is to enlarge the description of the only known single complete pes of a Tertiary megatherine and make comparisons with those of other members of the family. The complete pes of the specimen type of Pyramiodontherium bergi (MLP 2-66) is housed in the collection of Vertebrate Paleontology of the Facultad de Ciencias Naturales y Museo (Universidad Nacional de La Plata). It was found at the informally named "Araucanense" levels of Bajo de Andalhualá, Catamarca Province (Late Miocene-Pliocene), Argentina. The elements of the pes show the general characters of other megaterines; however, the astragalar depression is less deeper than M. americanum Cuvier; the calcaneum is more slender than E. laurillardi Lund; the navicular has two facets to articulate with the ectocuneiform; there are 7 separated tarsal elements (calcaneum, astragalus, navicular, entocuneiform, mesocuneiform, ectocuneiform, and cuboid) while in other megaterines that know the pes, usually the mesocuneiform and the entocuneiform are fused into a single element termed the mesoentocuneiform complex; the third digit is formed only by two phalanxes, the proximal phalanx results from the fusion of two phalanxes; digit IV, unlike what happens in every Quaternary megatherine, has the three phalanxes. The presence of entocuneiform and mesocuneiform separados and three phalanxes in the digit IV, are interpreted como plesiomofic states of the characters presente (Observados) in the Plio-Pleistocene genera, The plesiomorphic-apomorphic characters observed here could be help to solve the polytomy proposed by De Iuliis, and a more precise knowledge of the way the states of the characters were changed.