Nearly all herbivorous saurischians were sauropodomorphs. The first large dinosaurian herbivores were early sauropodomorphs, the prosauropods (“before lizard feet”). Prosauropods had a well-developed thumb claw, a long neck, and numerous leaf-shaped teeth. Most could walk on either two legs or four. Some forms (Thecodontosaurus, Anchisaurus) were one or two meters long, but several species (Plateosaurus, Riojasaurus) reached three times this size. Prosauropods were common in the Late Triassic and Early Jurassic, but were extinct by the Middle Jurassic.

The sauropods ("lizard feet") were the largest known terrestrial animals, and are among the most recognizable dinosaurs. These animals were characterized by long tails, small heads, and long necks (with extra vertebrae as well as very long vertebrae). Walking on four columnar limbs, they reached 30 meters in length, and weighed perhaps 50 tons. The earliest sauropods are from the Late Triassic, but they did not become common until the Jurassic, and lasted until the end of the Cretaceous.

Theropods ("beast feet") include some of the most famous and popular dinosaurs. All carnivorous dinosaurs are theropods, and as such they retain the pointed, serrated teeth of their ancestors. Theropods also evolved new features, including a joint in the lower jaw to act as a shock absorber (or perhaps for increased mobility). Some theropods developed additional openings in the skull, fewer fingers, and feathers. Ranging in size from a few kilograms to several tons, and from one to 15 meters in length, theropods lived from the Late (or perhaps Middle) Triassic through to the end of the Cretaceous. Theropods include the oldest known dinosaurs (Herrerasaurus and Eoraptor) and the largest bipeds (Tyrannosaurus, Giganotosaurus,and Carcharodontosaurus). One very specialized group of theropods—birds—became endothermic and developed the ability to fly.

To Learn more about saurischians, please visit our Tree of Life Interactive