Hypothetical lung structure of Brachiosaurus (Dinosauria: Sauropoda) based on functional constraints

Comparison of avian and crocodylian lung structure suggests a basic archosaurian structural type, consisting of four rows of chambers that radiate independently from an intrapulmonary bronchus. The later structure is cartilage‐reinforced cranially. Caudally, the cartilage reinforcement diminishes and the radiating pattern of tubular chambers becomes irregular. The presence of extensive pneumatic spaces in the dorsal vertebrae combined with the extremely large size of Brachiosaurus suggests that the dorsal margin of the lungs was strongly attached to the body wall, thus restricting lung inflation in this region. By analogy with similarly structured testudine lungs, it is highly probable that the ventral part of the very large and cavernous lungs consisted of sac‐like chambers, which acted as air reservoirs and also ventilated the gas exchange tissue, which was concentrated dorsally.