Air sacs are spaces within an organism where there is the constant presence of air. Among modern animals, birds possess the most air sacs (9–11), with their extinct dinosaurian relatives showing a great increase in the pneumatization in their bones. Birds use air sacs for respiration as well as a number of other things. Theropods, like Aerosteon, have many air sacs in the body that are not just in bones, and they can be identified as the more primitive form of modern bird airways. Sauropods are well known for the large number of air pockets in their bones, although one theropod, Deinocheirus, shows a rivalling number of air pockets.
Diagram showing the general layout of air sacs in a bird
An emperor penguin, an example of a diving bird
Comparison between the air sacs of Majungasaurus and a bird
The uncinate processes are the small white spurs about halfway along the ribs. The rest of this diagram shows the air sacs and other parts of a bird's respiratory system:1 cervical air sac, 2 clavicular air sac, 3 cranial thoracal air sac, 4 caudal thoracal air sac, 5 abdominal air sac (5' diverticulus into pelvic girdle), 6 lung, 7 trachea
Sauropoda, whose members are known as sauropods, is a clade of saurischian ('lizard-hipped') dinosaurs. Sauropods had very long necks, long tails, small heads, and four thick, pillar-like legs. They are notable for the enormous sizes attained by some species, and the group includes the largest animals to have ever lived on land. Well-known genera include Apatosaurus, Argentinosaurus,
Alamosaurus, Brachiosaurus, Camarasaurus, Diplodocus, and Mamenchisaurus.
Sauropoda
Reconstruction of Ampelosaurus
Some sauropods, such as Alamosaurus sanjuanensis, formed herds segregated by age.
Cast of Toni, a juvenile brachiosaurus (restored as a diplodocid)
