Sublime recapitulation: Evolution of the appendicular skeleton of Australian Mekosuchinae crocodiles.

Australian mekosuchines (Crocodylia; Crocodyloidea) with their wide diversity of cranial shape and inferred hunting strategies present a fascinating window into the diversification processes of crocodilians. This includes lingering questions as to the extent of any terrestrial habitus. A direct morphological signal for locomotion can be expected in the postcrania, particularly the girdles and the limbs of the appendicular skeleton. After a lengthy survey, enough materials of the pelvic girdle are available to chart morphological variation in the subfamily from Eocene through to middle Miocene. Over this period, the pelvis has undergone a vigorous morphological radiation. An enclosed, ventrally oriented acetabulum in the ilium developed in one lineage that apparently recapitulates the pillar-erect configuration of the pelvic girdle seen in many Mesozoic crocodilian lineages, suggesting consistent use of erect high-walk in these mekosuchines. Other pelves from Oligo–Miocene deposits display morphology closer to modern crocodilians despite clearly representing derived forms themselves, indicating a partition of locomotory strategy in the fauna during the Oligo–Miocene. While materials of hindlimb remain frustratingly lacking in light of this discovery, enough materials of forelimb humeri have been uncovered to chart the morphological variation in the subfamily from Eocene through to Pleistocene, corroborating what is seen in the pelvic girdle. As such, a collaborative project has been started that aims to quantitatively asses shape and stress variation in the mekosuchine forelimb using geometric morphometric and finite element analyses.