How It Works-Book Of Dinosaurs

Dinosaurs can be split into two major

Classifi cation groups, with many more subdivisions

49

The meat-eating

dinosaurs walked

on two feet

All the carnivorous dinosaurs were

theropods (although not all theropods

were carnivores) and walked upright

on their two hind legs. They typically

had hollow bones, three main fi ngers

on each hand and foot, and sharp,

curved teeth and claws used for

hunting and eating.

50

Dinosaurs

either had

lizard hips or bird hips

Dinosaurs can be divided into two

major groups based on their

hipbones. The Ornithischia, or

‘bird-hipped’ dinosaurs had a pubic

bone that pointed toward the tail,

and the Saurischia, ‘lizard-hipped’

dinosaurs pointed toward the head.

Interestingly, birds evolved from

lizard-hipped dinosaurs.

51

Most dinosaurs

ate plants

Dinosaurs are often portrayed as

fearsome hunters, but the majority of

species were herbivores. Even some

of the ferocious-looking theropods

actually ate plants and used their

sharp claws for digging.

56

Dinosaurs

lived during

the Mesozoic Era

Dinosaurs ruled the Earth for 165

million years, in a time period

known as the Mesozoic Era. This

era can be split into three periods,

Triassic, Jurassic and Cretaceous

57

Dinosaurs fi rst

appeared 230

million years ago

Dinosaurs evolved during the

Triassic period, between 250 and

200 million years ago. The warm,

dry conditions were perfect for

breeding reptiles.

59

Early dinosaurs

lived on the

continent of Pangaea

When dinosaurs fi rst appeared, the

landmasses of the Earth were joined

into a supercontinent called Pangaea.

This later fractured into two continents

• Laurasia and Gondwana.

58

Volcanic eruptions

contributed to the

extinction of the dinosaurs

Huge lava fl ows are present in the fossil record for

about 500,000 years before the extinction of the

dinosaurs, and many scientists think eruptions

contributed to their extinction by fi lling the air

with a thick cloud of ash.

TRIASSIC 252–201 MILLION YEARS AGO JURASSIC 201–145 MILLION YEARS AGO

Dinosauria

Tyrannosauridae

family tree

ALLOSAURUS

CAMPOSAURUS

CERATOSAURUS

SAURISCHIA

ORNITHISCHIA

Cerapoda

Theropoda

Sauropodomorpha

Plateosauridae

Allosauroidea

Carcharodontosauria

Metriacanthosauridae

Sauropoda

Ceratosauridae

Thyreophora

Heterodontosauridae

Marginocephalia

Ankylosauria

SINRAPTOR

PLATEOSAURUS

RIOJASAURUS

HUAYANGOSAURUS

FRUITADENS

STEGOSAURUS

Ornithopoda

Stegosauria

Q Gorgosaurus Q Daspletosaurus Q Albertosaurus Q Tarbosaurus Q Tyrannosaurus

DINOSAURS’ LEGACY

101 dinosaur facts

Camposaurus

Late Triassic

North America

Riojasaurus

Late Triassic

South America

Apatosaurus

Late Jurassic

North America

Torvosaurus

Late Jurassic,

North America,

Europe

Stegosaurus

Late Jurassic

North America,

Europe