Ontogeny of the post ‐cranial axial skeleton of Melanosuchus niger (Crocodylia, Alligatoridae)

This study proposes the description of the development of the post‐cranial axial skeleton, including vertebrae, gastralium, ribs, sternum and interclavicle, in Melanosuchus niger. Six nests were marked and two eggs removed from each nest at 24‐hour intervals until hatching. For post‐hatching evaluation, 30 hatchlings were kept in captivity and one exemplar was euthanized at three‐day intervals. Samples were diaphanized using potassium hydroxide (KOH), alizarin red S and Alcian blue. A routinely generally used method was applied for histological evaluation. It was difficult to define in which vertebrae the development of cartilaginous centers began, but it was possible to observe that this condensation advanced in the craniocaudal direction. The condensation started in the vertebral arches and was visibly stronger in the cervical and dorsal regions, advancing to the lumbar, sacral and, last, to the caudal region. The atlas showed a highly different morphology compared with the other cervical vertebrae, with a short intercenter, two neural arches, and a proatlas. The ossification process began in the body of cervical vertebrae III to VIII and alizarin retention decreased in the last vertebrae, indicating a craniocaudal direction in bone development, similar to cartilage formation. In the histological sections of gastralium and interclavicles of M. niger at several development stages, it was possible to observe that these elements showed intramembranous development. This...
Source: The Anatomical Record Part A: Discoveries in Molecular, Cellular, and Evolutionary Biology - Category: Molecular Biology Authors: Tags: Full Length Article Source Type: research