Abstract

ELISSAMBURU, A.  and  VIZCAINO, S.F.. Morphometric differentiation of the humerus and femur of Pliocene and early Pleistocene Paedotherium species (Mammalia, Notoungulata). Ameghiniana [online]. 2005, vol.42, n.1, pp.159-166. ISSN 1851-8044.

The genus Paedotherium includes small rodent-like ungulates that are distinguished by characters of the skull and teeth. Morphofunctional differences in the appendicular skeleton of P. bonaerense Ameghino and P. typicum Ameghino (Pliocene- early Pleistocene) suggest that appendicular characters can be used in specific identification. In this contribution, morphometric differences between the humerus and femur are analysed. Five humeral and six femoral measurements are taken from 29 specimens. They include functional length (LH), deltoid length (LDH), transverse and anteroposterior diameter (DTH, DAPH) and epicondilar diameter (DEH) for the humerus, and functional length (LF), proximal length to the third trochanter (LTTF) and to the lesser tuberosity (LTmF), transverse and anteroposterior diameter (DTF, DAPF) and epicondilar diameter (DEF) for the femur. Data are analysed by comparison of means, principal components analysis (PCA), discriminant analysis (DA) and correlation with body mass. Paedotherium bonaerense and P. typicum show differences in DEH, with higher values for the former, and in LF and LTTF, with higher values for the latter. The humerus is more important than the femur in differentiating between the species. As shown by the multivariate analysis, the association between DEH and LH provides the best discriminator between the species. In the femur, LF and LTTF are associated with the variation of DTF, DEF and body mass. DA shows the importance of the humerus for discriminating between the species, and that the femur is a poor discriminator, probably due to the influence of body mass on the linear data.

Keywords : Paedotherium; Morphometry; Humerus; Femur; Species identification.