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01. Winton Wonders

CLASSIFICATION OF DINOSAURS

WHAT IS A DINOSAUR?

In Ancient Greek the word dinosaur means ‘terrible lizard’. Dinosaurs belonged to a group of animals that includes birds, crocodiles and other prehistoric animals such as pterosaurs. All of these animals are called the ‘archosaurs’, a group of reptiles that first appeared about 250 million years ago (Ma).

Like other reptiles, dinosaurs had tough scaly skin, although smaller species sometimes had a soft feathery down similar to ducks, and others were covered in long and elaborate feathers. Most dinosaurs laid shelled eggs in nests and some may have cared for their young.

Dinosaurs lived in the Mesozoic era between 230 and 65 Ma. They had four limbs, lived on land, and breathed air. Dinosaurs were bipedal (walked on two legs) or quadrupedal (walked on four legs). Some ate plants; others were fearsome carnivores (meat-eaters); while others may have been omnivores (eating both plants and animals). Many dinosaurs had great armoured plates and shields which helped them fend off predatory dinosaurs. Some developed the ability to fly, eventually evolving into modern birds. The only living descendants of the dinosaurs are the birds.

TYPES OF DINOSAURS

Scientists who study fossils and pre-historic life are called palaeontologists (pronounced pay-leon-tol-o-gists). They divide dinosaurs into two main groups, based on the shape of their pelvic (hip) bones.

Early scientists realised that the hip bones of dinosaurs were similar to the skeletons of two groups of living animals – lizards and birds. They made two distinct orders of dinosaurs, the Saurischia (lizard-hipped) and the Ornithischia (bird-hipped). Strange as it may seem, birds evolved from the lizard-hipped group of dinosaurs.

Theropod dinosaur of the Jurassic Period eating a smaller ornithopod Theropod dinosaur of the Jurassic Period eating a smaller ornithopod.
Artist: S. D. Elmer, © Queensland Museum.