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.