Sauropodomorpha: Encyclopedia II - Sauropodomorpha - Description

Sauropodomorpha - Description

Sauropodomorphs were adapted to browsing high among the trees, and most of their defining characteristics support this feeding strategy. A light, tiny skull on the end of a long neck (with ten or more elongated cervical vertebrae) was balanced by a long tail (with one to three extra sacral vertebrae) when reaching high above the ground.

Their teeth were weak, and shaped like leaves or spoons (lanceolate or spatulate). Their jaws became like scissors in the sauropods, for chopping off vegetation. Instead of grinding teeth, they had stomach stones (gastroliths), similar to the gizzard stones of modern birds and crocodiles, to help digest tough plant fibers. The front of the upper mouth bends down in what may be a beak.

The first known sauropodomorph, Saturnalia, was small and slender (1.5 m, or 5 ft long), but by the end of the Triassic they were the largest dinosaurs of their time, and kept growing. Ultimately the largest sauropods like the Supersaurus, Brachiosaurus, and Argentinosaurus reached 30–40 m (100–130 ft) in length, and 60,000–100,000 kg (65–110 tons) or more in mass.

They were originally bipedal, but as their size increased they quickly came to prefer the quadrupedal position, and rose up on their hind legs only to feed from high tree branches. Some early sauropodomorphs may have been omnivores; it is almost certain that their shared ancestor with the other saurischian lineage, the theropods, was a carnivore.

They also had large nostrils (nares), and retained a thumb (pollux) with a big claw which may have been used for defense — though their primary defensive adaptation was sheer size.

Adapted from the Wikipedia article "Description", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki