Dyrosaurids have a unique postcranial anatomy

Dyrosauridae is a family of neosuchian crocodyliformes known from both terrestrial and aquatic environments across the Cretaceous–Palaeogene transition. The postcranium of dyrosaurids comprises astonishing features such as their vertebra with hypapohyses and tall neural spines, their well-developed pelvic girdles, and stout limbs, etc. However, their postcranial anatomy has long been overlooked, obscuring both their locomotive adaptations and the magnitude of their disparity. From this point of view, we thoroughly analysed the entire anatomy of the key dyrosaurids Congosaurus bequaerti and Hyposaurus natator, along with other extant (Crocodylia) and extinct Crocodyliformes (Thalattosuchia). In parallel, we also produced a comprehensive dataset of 187 traits on 27 taxa, largely covering the cranium and postcranium of exemplar crocodyliforms. These data were analysed following principal coordinate analysis (PCoA) to envision the morphospace occupation of Dyrosauridae, Thalattosuchia and Crocodylia. Our data report that Dyrosauridae displays a unique postcranial architecture, considerably contrasting with that of Crocodylia, but in some ways not totally dissimilar from that of Thalattosuchia. Consequently, extant crocodylians might not represent a good functional analogue for extinct crocodyliformes. Furthermore, phylogenetic and disparity analyses would benefit from the employment of more postcranial data.SEA Croc