 Researchers have presented evidence and arguments for air sacs in sauropods, "prosauropods", coelurosaurs, ceratosaurs, and the theropods "Aerosteon" and "Coelophysis".In advanced sauropods ("neosauropods") the vertebrae of the lower back and hip regions show signs of air sacs.In early sauropods only the cervical (neck) vertebrae show these features.