An important discovery has been made by researchers at Stony Brook University, led by Dr. James Napoli. Their study, published in Nature, challenges previous beliefs about the evolution of flight in dinosaurs. The team found that theropod dinosaurs had a type of carpal bone in their wrists known as the pisiform, which is considered crucial to flight in birds.
For years, scientists were puzzled about one particular carpal bone in bird wrists until it was identified as the pisiform. This bone originally acted like a kneecap and moved to replace another wrist bone called the ulnare. In modern birds, its position helps them fold their wings automatically when flexing their elbows and prevents dislocation during flight.
The study focused on two types of dinosaur fossils: a troodontid and an oviraptorid. The research was possible due to exceptional fossil preservation and high-resolution CT scanning technology. The specimens were provided through collaboration with the American Museum of Natural History and the Mongolian Academy of Sciences.
Napoli stated, "We believe this is the first time a migrated pisiform in a non-bird meat-eating dinosaur has been identified." He added that more research is needed to explore how many times dinosaurs might have developed flight capabilities.
Their findings indicate that these bird-like wrist structures appeared not just within birds but earlier among Pennaraptora—a group of theropods including Velociraptors and other feathered dinosaurs where bird-like traits began to emerge.
Napoli concluded that understanding these evolutionary developments sheds light on how avian features evolved much deeper in theropod history than previously thought.