Key Points A recent study highlights the overlooked importance of the fibula in bird mobility and evolution. Researchers used X-rays and 3D modeling to examine bird joints and movements. Early bird ancestors like Rahonavis showed evolutionary traits that led to bird-like mobility. Evolution adapted stiffened dinosaur legs into flexible, bird-like joints. Yale paleontologists have uncovered a critical evolutionary connection between dinosaurs and modern birds by examining the leg bone structures—specifically the fibula, a slender bone in the lower leg. This...