Early Crocodylomorpha

Abstract

Non-crocodyliform crocodylomorphs, often called ‘sphenosuchians’, were the earliest-diverging lineages of Crocodylomorpha, and document the stepwise acquisition of many of the features that characterize extant crocodylians. The first crocodylomorph fossils are approximately 230 million years old (upper Carnian, Late Triassic), and at least one of these early lineages persisted until at least 150 million years ago (Late Jurassic). These taxa occupied a wide variety of terrestrial environments from equatorial regions to high-paleolatitudes during the early Mesozoic. Despite a quarter-century of quantitative phylogenetic work, the interrelationships of early crocodylomorphs remain in a state of flux, though recent studies suggest that these lineages are paraphyletic with respect to Crocodyliformes, rather than forming a monophyletic early offshoot of Crocodylomorpha as some previously hypothesized. Nearly all early crocodylomorphs were upright quadrupedal small-bodied taxa, but lumping them all together as small cursorial faunivores masks ecological and morphological disparity in diet and limb functional morphology. With the accelerated pace of recent discovery of new specimens and taxa, future consensus on early crocodylomorph phylogeny will provide a solid framework for understanding their change in diversity and disparity through time, potential biogeographic patterns, and the morphological transformation leading to Crocodyliformes.

Convergence and functional evolution of longirostry in crocodylomorphs

“…Soon after the origin of the clade, basal crocodylomorphs already exhibited a remarkable spectrum of skull morphologies suggesting disparate feeding modes (Irmis et al . ). Crocodylomorphs radiated throughout the Jurassic and Cretaceous, with many lineages occupying diverse ecological niches on land, in the sea and in semiaquatic environments (Bronzati et al .…”

Detailed anatomy of the braincase ofMacelognathus vagansMarsh, 1884 (Archosauria, Crocodylomorpha) using high resolution tomography and new insights on basal crocodylomorph phylogeny

“…Drymala & Zanno (2016) recognized the presence of a well defined antorbital fossa, all around its circumference, in what they defined as the “group H” which clustered the referred specimens of Hesperosuchus ( H . “ agilis ” sensu Nesbitt, 2011 and Irmis, Nesbitt & Sues, 2013) and Dromicosuchus . Among basal crocodylomorphs, this trait was also observed in Kayentasuchus (Drymala & Zanno, 2016).…”

“…Later on, Clark, Sues & Berman (2000) described a much more complete individual from the upper part of the Chinle Formation and assigned it Hesperosuchus . However, Nesbitt (2011) and Irmis, Nesbitt & Sues (2013) thought this to be unlikely as it would extend the range of the same species through the entire deposition of the Chinle Formation, possibly as long as 20 million years. In later contributions other authors have mentioned and even scored some differences between both specimens (Drymala & Zanno, 2016).…”

O estudo dos répteis fósseis-cresce a contribuição da ciência brasileira

“…Eram formas relativamente pequenas com um comprimento em torno de 1 metro e de esqueleto delicado, conjuntamente classificados dentro de Sphenosuchia. Apesar de caminhar nas quatro patas, teriam o esqueleto ereto e foram encontrados sobretudo na Argentina e nos Estados Unidos (30). Também no Brasil existe um réptil que pode estar ligado a origem dos crocodilomorfos: Barberenasuchus brasiliensis Mattar, 1987.…”

“…Também no Brasil existe um réptil que pode estar ligado a origem dos crocodilomorfos: Barberenasuchus brasiliensis Mattar, 1987. No entanto, a sua posição filogenética é tida como controversa (30).…”