The ontogenetic pattern of neurocentral suture closure in the axial skeleton of Hyperodapedontinae (Archosauromorpha: Rhynchosauria) and its evolutionary implication

Understanding ontogeny of a taxon is a crucial step to properly elucidate its taxonomy and evolution. However, aside from histological data, osteological criteria for assessing maturity are considered lineage specific or controversial. The sequence of neurocentral suture closure of the axial skeleton of extant crocodilians, which occurs in a postero-anterior sequence, has being used as a non-destructive method to determine maturity in extinct reptiles. However, the use of this criterion in extinct archosaurs not closely related to crocodilians is debatable, as the ancestral condition of Archosauria is unknown and variation occurs in timing and sequence orientation within the clade. We have assessed the pattern of neurocentral suture closure of the Hyperodapedontinae rhynchosaurs, an early archosauromorph clade distantly related to archosaurs. Different from extant crocodilians, they exhibit an antero-posterior sequence neurocentral suture closure. Relative size and other ontogenetic mar...