Figure 1

Pelvic morphology and evolution of hip joint articular morphology within archosaurs. A, time-calibrated phylogenetic tree based on the Nesbitt et al.61 tree shows the rapid diversification of archosaurs in the Lower Triassic. B, pelvic girdles of various stem-archosaurs and archosaurs. C, evolution of hip joint articular morphology based on the Ezcurra36 topology. Note the difference in the inferred ancestral posture for Archosauria and Pseudosuchia depending on the tree topology. Depicted taxa from top to bottom: Proterosuchus, redrawn from Ezcurra et al.82, Euparkeria, based on SAM PK 5867 and SAM PK 6047A, Phytosauria: Parasuchus, redrawn from Chatterjee83, Crocodylomorpha: Alligator, redrawn from Romer84, Rauisuchidae: Postosuchus, redrawn from Chatterjee85, Poposauroidea: Poposaurus, redrawn from Schachner, Manning & Dodson86, Aetosauria: Stagonolepis, redrawn from Walker87, Ornithosuchia: Ornithosuchus, redrawn from Sereno2, Aphanosauria: Teleocrater, redrawn from Nesbitt et al.38, Sauropodomorpha: Plateosaurus, based on specimen GPIT1, Theropoda: Apteryx, redrawn from Schachner, Manning & Dodson86.