An analysis of theropod dinosaur fossils has revealed a type of carpal bone, known as the pisiform, in their wrists. This discovery could change scientists’ understanding of how flight evolved in dinosaurs. The research was led by James Napoli, PhD, from Stony Brook University and was published in Nature.
The study focused on two types of theropod dinosaurs: a troodontid and an oviraptorid. Researchers used high-resolution CT scanning to examine the wrist bones of these specimens. The findings suggest that the pisiform bone played a significant role in the evolution of flight by allowing birds to fold their wings automatically when the elbow flexes.
“We believe this is the first time a migrated pisiform in a non-bird meat-eating dinosaur has been identified,” said Napoli. He further explained that experimentation with flight appears only after the pisiform migrated into the wrist joint.
The research suggests that bird-like traits began to appear within a group called Pennaraptora, which includes dromaeosaurids like Velociraptor, troodontids, and oviraptorosaurs. This group saw flight evolve multiple times.
Napoli and his co-authors wrote that their results indicate “the topological and functional replacement of the ulnare by the pisiform occurred much deeper in theropod history than has been previously understood.”
