Sauropodomorphs

Respiratory system

Sauropodomorphs likely had a heterogenous respiratory system. This means that there were multiple organs responsible for the process of respiration that served different functions. The lungs themselves would have been filled with the parenchymal tissues necessary for oxygen to diffuse into the blood. However, secondary organs, the air sacs, would have been involved in helping to circulate air through the lungs, but they probably lacked parenchymal tissues and would not have been used to absorb oxygen into the blood directly. This style of respiratory system is seen in modern birds and some squamates and was likely present in both sauropodomorphs and non-avian theropods. The lungs of sauropodomorphs were likely directly attached to the spine, which is evidenced by the presence of invasive tissues in the dorsal vertebrae which were possibly diverticula of the lungs themselves. Sauropodomorphs likely possessed large air sacs in front of and behind the lungs, which is the condition seen in modern birds. These are called the cervical (front) and abdominal (back) air sacs, respectively, and they would have assisted the circulation of air through the lungs in the absence of a diaphragm (which sauropodomorphs did not have). More advanced sauropods may have possessed additional air sacs in the head, tail, shoulder, and hip regions of the body, although this remains uncertain due to the difficulty in interpreting the presence of various pneumatic structures in their bones.