Aerosteon: A theropod with pneumatic bones

Aerosteon is a theropod dinosaur from Late Cretaceous Argentina, measuring approximately 9 meters in length. Its name means "air bone," reflecting the discovery of extensive pneumatic cavities within its skeleton. These air-filled structures resemble the respiratory system of modern birds, indicating that Aerosteon possessed an efficient, air sac–assisted breathing system. This finding provides direct evidence for the evolution of dinosaur respiration and supports the hypothesis that dinosaurs had bird-like unidirectional airflow lungs. As a member of the Megaraptora, Aerosteon's pneumatic bones not only reduced body weight but may also have aided in thermoregulation. This discovery marks a major advance in our understanding of dinosaur physiology.