birds

Similar sex differences have been seen in other animals, including fruit flies, rats, zebrafish and birds.

Wings may be the obvious choice when studying the connection between dinosaurs and birds, but a pair of Yale paleontologists prefer drumsticks.

"This shortened fibula is what allows birds to twist and turn around when they're not in flight. And to understand its evolutionary story, we have to look at dinosaurs."

They also collected X-ray videos from an iguana and an alligator and examined the shapes of leg bones in other birds, including a penguin, an ostrich, an owl, and a crane.

The researchers found that in birds, the tibial joint surfaces have curved arcs, and the shortened fibula is able to roll within the bird's drumstick for about its length relative to the tibia.