The name "dinosaur" covers all members of the orders, Saurischia and Ornithschia. Sometimes they are grouped together in a "superorder" called Dinosauria. Surprisingly, this does not cover the so-called "flying dinosaurs" (pterosaurs) or "swimming dinosaurs" (ichthyosaurs, mososaurs and so on.)

Saurischia
Dinosaurs of the order Saurischia (Saurischian dinosaurs) can be identified by the lizard-like structure of their hips. Their pelvises were thinner and squatter than their relatives the Ornithschia. This order includes two major groups, the theropods and the sauropods.

THEROPODS
This suborder included all the carnivorous dinosaurs, such as Allosaurus and Compsognathus. All theropods were bipedal, with three-toed feet and a wishbone. Some were omnivorous or herbivorous, and many had feathers.

Most of them became extinct 65 million years ago, although technically modern birds can be classified as theropods.

SAUROPODS
The sauropods are the long-necked quadrupedal dinosaurs epitomised in Apatosaurus (formally Brontosaurus). They ranged in size from the titanic Supersaurus, at 40 metres, to the underwhelming 5-metre dwarf sauropods.

Ornithschia
Dinosaurs of this order can be identified by the more bird-like structure of their hips. They also had beaks and in some cases duck-bills, but are not thought to be the ancestors of modern birds (unlike theropods). Ornithschian dinosaurs were generally smaller than Saurischians and entirely herbivorous, probably living in herds. Famous plated and bony dinosaurs, like Ankylosaurus and Stegosaurus were members of this order.