Carpal-metacarpal specializations in burrowing South American octodontoid rodents

MORGAN, C.C.; VERZI, D.H.

Punta del Este

Congreso; 9th International Congress of Vertebrate Morphology; 2010

International Society of Vertebrate Morphology

Morphology of the carpus and metacarpus of extinct and living octodontoids was analyzed withthe goal of detecting morpho-structural specializations related to scratch-digging. The sampleincluded the ctenomyids Ctenomys spp., †Eucelophorus cabrerai (subterranean), †Actenomyspriscus (fossorial), the octodontids Octodontomys gliroides, Octodon spp., Octomys mimax,Aconaemys porteri (fossorial) and Spalacopus cyanus (subterranean), and the echimyidsThrichomys apereoides, Proechimys poliopus (epigean), Euryzygomatomys spinosus andClyomys laticeps (fossorial). Within a context of relative morphological uniformity, we detectedthe following specialized traits in the burrowing Spalacopus, Clyomys, Ctenomys and†Eucelophorus: broad shortened carpus, predominance of ray 3 (mesaxony), robust metacarpals,and markedly broad and short metacarpal V. In addition, the specialized subterranean Ctenomyspresented an enlarged scapholunar in extensive contact with the unciform, and with complexshapedproximal articular surface. These features are interpreted as responses to mechanicalrequirements of scratch-digging, providing greater carpal rigidity and resistance to direct forcesexerted during the digging stroke. In Ctenomys, the radius-scapholunar joint restricts movementat wrist level.