Fossil Study Reveals Dinosaur Leg Evolution Key to Bird Mobility

New Yale research uncovers how a shortened fibula in dinosaurs enabled the unique knee mobility seen in modern birds like turkeys and penguins.

Yale researchers identified the evolutionary significance of a shortened fibula in bird ancestors, which allows modern birds to twist and maneuver on the ground.
Using X-ray videos of birds like the helmeted guineafowl and 3D modeling, scientists visualized how bird knee joints maintain smooth motion even during extreme twisting.
Comparisons with reptiles such as iguanas and alligators revealed that bird fibulas move differently, enabling unique mobility for activities like mating displays and prey gathering.
Fossil evidence from avian ancestors, including Rahonavis ostromi and Ichthyornis dispar, showed early adaptations for flexible knee joints, unlike the stiffened knees of larger dinosaurs like Tyrannosaurus rex.
The study highlights how evolutionary structures are often repurposed, with the fibula's transformation playing a critical role in bird locomotion and behavior.