El tipo scratch-digger en dos armadillos (Dasypodidae, Xenarthra): ontogenia esqueletaria de las manos y variaciones de dígitos

Fernando C. Galliari

doi:10.24215/25456377e212

Authors

Fernando C. Galliari División Paleontología de Vertebrados, Museo de La Plata, Facultad de Ciencias Naturales y Museo, Universidad Nacional de La Plata - CONICET

DOI:

https://doi.org/10.24215/25456377e212

Keywords:

Appendicular skeleton, preosteogenic autopodium, Chaetophractus, Dasypus,

Abstract

Ontogenetic and comparative studies on the hand skeleton of armadillos (Dasypodidae, Xenarthra) are scarce. In this paper adult autopodial skeleton of two species of extant armadillos, Dasypus hybridus (Dasypodinae) and Chaetophractus villosus (Euphractinae), are characterized. In addition, fetal morphology of the cartilaginous hands is compared to that of the bony adult hands. Adult specimensincluded 38 skeletons of C. villosus (n=34), and D. hybridus (n=4). Fetal cartilaginous hands were studied from serial histological sectioning of two specimens, belonging to D. hybridus and C. villosus. A comprehensive description of the adult hand skeleton, and a qualitative comparison with the fetal hand of both species is provided. The hand of C. villosus is clearly pentadactylous, being the third finger the larger one. In the carpus, elements are largely interlocked betwen them, and with the metacarpals. Therefore, this species fits well into the scratch-digger category. In contrast, D. hybridus shows a reduced five digit, narrowing the entire hand, and there is a similar size of digits II and III. This condition is tie to a series of modifications in the carpus, including a less contact among carpals and metacarpals. Fetal carpus of C. villosus is similar to adult skeleton, while in D. hybridus some differences are recorded. Considering that a relict of the fifth finger is present in D. hybridus, the presence of this finger as a diagnostic character of D. (Hyperoambon) kappleri should be discarded. In addition, a comprehensive revision of this character should be extensive to the rest of the species of Dasypus.

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