title: Ontogeny of the Appendicular Skeleton in Melanosuchus niger (Crocodylia: Alligatoridae).
abstract: The objective of the present study was to analyze chondrogenesis and the ossification pattern of the limbs of Melanosuchus niger in order to contribute with possible discussions on homology and the fusion pattern of autopodial elements and phylogeny. In the Reserva Extrativista do Lago Cuniã, Rondônia, Brazil, six nests were marked and two eggs removed from each nest at 24-hour intervals until hatching. Embryos were cleared using KOH; bone tissue was stained with alizarin red S and cartilage with Alcian blue. Routine staining with HE was also performed. In the pectoral girdle, the scapula showed ossification centers before the coracoid process. In the pelvic girdle, the ilium and the ischium were condensed as a single cartilage, although ossification took place through two separate centers, forming distinct elements in the adult. The pubis developed from an independent cartilaginous center with free end, which reflects its function in breathing. In the initial stages, the stylopodium and the zeugopodium developed from the condensation of a Y-shaped cartilage in the limbs, and differentiation of the primary axis and digital arch were observed. The greatest changes were observed in the mesopodia. In their evolution, Crocodylia underwent a vast reduction in the number of autopodial elements as a consequence of fusions and ossification of some elements. This study shows that the chondrogenesis and ossification sequences are dissociated. Moreover, the differences between M. niger and other species show clear variation in the patterns for these events in Alligatoridae.
authors: 1 Laboratório de Ensino e Pesquisa em Animais Silvestres, Federal University of Uberlândia, Uberlândia, Brazil.
authors: Lucélia Gonçalves
authors: LG
authors: Vieira
authors: 1 Laboratório de Ensino e Pesquisa em Animais Silvestres, Federal University of Uberlândia, Uberlândia, Brazil.
authors: André Luiz Quaqliatto
authors: AL
authors: Santos
authors: 2 Laboratório de Anatomia Humana e Comparativa, Federal University of Goiás, Jataí, Brazil.
authors: Fabiano Campos
authors: FC
authors: Lima
authors: 3 Centro Nacional de Pesquisa e Conservação de Répteis e Anfíbios - RAN/ICMBio, Lagoa Santa, Brazil.
authors: Sônia Helena Santesso Teixeira de
authors: SH
authors: Mendonça
authors: 1 Laboratório de Ensino e Pesquisa em Animais Silvestres, Federal University of Uberlândia, Uberlândia, Brazil.
authors: Lorena Tannus
authors: LT
authors: Menezes
authors: 4 Laboratório de Biologia Animal, University of Brasília, Brasília, Brazil.
authors: Antônio
authors: A
authors: Sebben
mesh_terms: D000489:Alligators and Crocodiles / Q000033:anatomy & histology / Q000254:growth & development*; D000818:Animals; D001846:Bone Development / Q000502:physiology*; D020219:Chondrogenesis / Q000502:physiology*; D005552:Forelimb / Q000254:growth & development*; D006614:Hindlimb / Q000254:growth & development*
keywords: Archosauria; alizarin; black caiman; development; embryo