Morphofunctional analysis of the postcranial skeleton of Neoreomys australis (Rodentia, Caviomorpha, Dasyproctidae) from the Miocene of Patagonia

CANDELA, ADRIANA M.* AND VIZCAÍNO, SERGIO F

Paris

Congreso; 6 Th International Congress of Vertebrate Morphology; 2007

University of Paris VI (P&M Curie)

The postcranial skeleton of the extinct Dasyproctidae has not been evaluated from a functional-adaptative perspective. Morphofunctional analysis of the well-preserved postcranial bones of Neoreomys australis, one of the most abundant Miocene dasyproctids from Patagonia, provides evidence to infer its locomotor behavior. Osteological and myologycal features of the extant species were used as a model to interpret the functional significance of the postcranium of N. australis. Several postcranial features of this species are functionally compatible with cursorial habits: the humeral tuberosities, specially the greater tuberosity, are higher with respect to the humeral head, restricting the mobility of the gleno-humeral joint; the humero-ulnar and humero-radial joints limit pronation/supination movements at the elbow joint and increase the stability during flexion/extension (e.g., the capitular tail and capitular eminence are well developed, in congruence with the enlargement of the subrectangular radial head, which is anterior with respect to the ulna). The shape of the hip, knee, and cruro-astragalar, calcaneo-astragalar, and astragalo-navicular joints would have limited the rotational movements, improving the flexion/extension (e.g., the greater trochanter is proximally projected, increasing the mechanical advantage of the glutei; the tibial tuberosity is anteriorly projected, improving the mechanical advantage of quadriceps femoris; the intercondylar tubercles enhance the stability; the internally concave posterior process offers a stop at the upper ankle joint; the anterior distal tibial spine acts as a stop to lateral movements; the distal portion of the calcaneus is elongated).