Desenvolvimento do esqueleto em embriões de Caiman yacare (Daudin 1802) (Crocodylia, Alligatoridae)

Abstract

The cranium is a singular structure to vertebrates, and their actual anatomy is the result of thousands years of evolution, so the main focus of morphological and systematic studies. Given the importance of their detailed study aimed to clarify the processes of formation of the cranium in embryos of Caiman yacare. Embryos were collected at regular intervals throughout the incubation period, which were later submitted to the protocol of clearing and staining bones by the method of Davis and Gore (1936). The ossification pattern in C. yacare following general parameters in reptiles and other tetrapods, where the first bones to ossify are those involved in primary functions such as eating, and they, the upper jaw, some elements of the lower jaw, the pterygoid, jugal, ectopterygoides and it includes teeth, later. The bones of the dorsal portion of the skull ossify later, showing a cranial fontanelle that remains until the time of hatching. The parietal, frontal and opsthotic bones have more than one ossification center that fuse during ontogeny. The occipital portion also does not form completely until the hatching, once the morphology of young individuals is very similar to that present in adults.