Inferring locomotor behavior in the Miocene porcupine Steiromys duplicatus Ameghino (Rodentia, Erethizontidae)

CANDELA, A. M.; PICASSO, M.; ABELLO, M. A.

Madryn

Otro; Reunión anual de comunicaciones de la Asociación Paleontológica Argentina; 2005

Asociación Paleontológica Argentina

Postcranial anatomy of porcupine is relatively poorly known and has not been evaluated from a functional-adaptative perspective. Postcranial bones, some of them exceptionally preserved, provide evidence to infer the locomotor behavior of Steiromys duplicatus Ameghino, one of the most abundant porcupines in the Miocene daunas of Patagonia. Osteological and myological anatomy of living porcupines was analyzed and used as a model to interpret the functional significance of the postcranium of S. duplicatus. Several features, specially those of the joints, are indicative of the ability of this porcupine to climb. The humeral head is rounded and the tuberosities are low, suggesting a mobile gleno-humeral joint, compatible with a broad range of movements; the delto-pectoral crest indicates a strong development of the pectoral muscle, which is particularly active during climbing in living porcupines; the humero-ulnar and humero-radial joints are indicative of pronation and supination movements; the well-marked lateral epicondylar ridge and the medially protruding medial entepicondyle suggest an important development of the muscles braquiorradial, supinator, flexor digitorum profundus, and pronator teres. The morphology of the hip, knee, and cruro-astragalar, calcaneo-astragalar, and calcaneo-navicular joints would have allowed abduction and rotation movements; but in a lesser degree than the arboreal living Coendu spp. Some features of the foot of S. duplicatus (e.g., a large medial sesamoid bone, a medial orientation of the astragalar head) are indicative of grasping ability, but in a lesser degree then in Coendu spp.