Croc Ancestor Grows Into Biped

A newly described species, Sonselasuchus cedrus, known from hundreds of fossils in Arizona’s Petrified Forest, shows that juveniles walked on four legs while adults became bipedal because the hindlimbs continued to grow disproportionately. The finding implies that simple developmental changes (differential limb growth) can produce dramatic locomotor shifts and repeated convergent solutions like bipedalism in widely separated reptile lineages. — Shows that developmental (ontogenetic) pathways can create major functional and evolutionary changes, a useful concrete example for public conversations about evolution, convergence, and how small biological processes produce big anatomical outcomes.