The many acquisitions of bipedality in archosaurs

[Halichoeres]

This study maps inferred locomotory style onto the phylogeny of archosaurs and finds 7 distinct transitions from fully quadrupedal animals to fully bipedal animals within the clade. Importantly, there doesn't seem to be a requirement that they pass through a facultatively bipedal stage (that is, an animal that can go on two legs when it wants to, but normally doesn't). Here's a visual summary of the findings:


Red circles: fully bipedal
Yellow circles: fully quadrupedal
Blue circles: facultatively bipedal

open access in Royal Society Open Science: https://royalsocietypublishing.org/doi/10.1098/rsos.190569