Ontogenia dos ossos da cintura peitoral e membros torácicos em embriões de podocnemis unifilis

Abstract

The Testudines represent a small group that combines primitive and derived aspects, for example, in the skeleton of its members. To describe the ontogeny of the skeleton of the pectoral girdle and thoracic members of Podocnemis unifilis, 66 embryos were cleared. On the other side, the bones were stained to analyze the sequence of formation of their skeleton, which begins by the humerus, radius and ulna bones, by stage 20, all the bones of the pectoral girdle with colored centers of ossification at the end of this stage, in the same period when metacarpals also ossify, first by MCIV and MCIII, followed for bones MCII>MCI>MCV. Between stage 21 and 22, all phalanges have centers of ossification marked with alizarin; first the medial and distal phalanges, and finally the proximal phalanges. Only at the start of stage 24, the carpal ossification begins, first with the intermediate carpal bone, the distal carpal IV and central carpal III, followed by 25 others, where the pisiform is the last to make its center of ossification. The chronology of ontogenic events in different species of reptiles may differ substantially, but the pattern in P. unifilis is similar to the other Testudines.