Ontogeny of the Postcranial Axial Skeleton ofMelanosuchus niger(Crocodylia, Alligatoridae)

Abstract

This study proposes the description of the development of the postcranial 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-hr intervals until hatching. For posthatching 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. Anat Rec, 301:607-623, 2018. © 2017 Wiley Periodicals, Inc.

Developmental evolution of the distal ankle in the dinosaur–bird transition

“…The presence of a dt2 cartilage is relevant because in both of these species, dt2 is not present as an adult bone. A dt2 cartilage in Caiman yacare was also photographically documented and labeled in Fernández Blanco et al (2020), and previously also in other crocodilians, Alligator mississippiensis and Melanosuchus niger , where it is reported to become a fibrous tendon (Müller & Alberch, 1990; Vieira et al, 2016). However, in other species of Liolaemus , an embryonic dt2 cartilage is not observable in published photographs, or mentioned in any descriptions (Fabrezi et al, 2007), which suggests variable chondrification of this element within this genus.…”

“…The possibility that a prechondrogenic dt5 may fuse to mt5 in birds or in Caiman yacare seems less likely, since mt5 is not hook‐shaped, and is very reduced. However, this issue may deserve further exploration, given that early archosaurs did have a large, hook‐shaped mt5, and even the small‐sized mt5 of Crocodyliformes can be hook‐shaped as in Protosuchus , or wide and rounded as in the modern crocodilian Melanosuchus (Colbert & Mook, 1951; Vieira et al, 2016).…”

Phylogenetic Diversity of Ossification Patterns in the Avian Vertebral Column: A Review and New Data from the Domestic Pigeon and Two Species of Grebes

“…The vertebral arches more closely conform to the anteroposterior sequence, with the ossification starting from one cervical locus in the majority of hitherto studied species [ 13 ]. The strictly anteroposterior order of ossification of the vertebral bodies and arches is present in hitherto studied crocodylians, the extant sister group of birds—two alligatorids, Alligator mississippiensis [ 43 ] and Melanosuchus niger [ 44 ]. Unfortunately, our knowledge of the skeletogenesis of the vertebral column in fossil birds is very incomplete.…”

Método alternativo de tinción ósea en peces juveniles empleando extracto de Bixa orellana

“…La técnica de diafanización presenta grandes ventajas, principalmente para biólogos, sistemáticos y taxónomos, en la caracterización de especies y diferenciación de anormalidades óseas (Kihara, Ogata, Kawano, Kubota y Yamaguchi, 2002;Soliz y Ponssa, 2016;Vieira et al, 2018). Además, permite entender la ontogenia y los cambios que tienen los elementos óseos durante el desarrollo de un espécimen (Vieira et al, 2018). Esta técnica, propuesta por Simons y Van Horn, (1971), Dingerkus y Uhler (1977) consiste en una serie de procesos de aclaramiento de la muestra y tinción del tejido cartilaginoso y óseo.…”