The New Childrens Encyclopedia

LIVING WORLD

Sail-back synapsids

appeared.

PERMIAN
290250 MYA

The first dinosaurs,

early mammals,

turtles, and frogs

appeared.

TRIASSIC

250200 MYA

The first bird,

Archaeopteryx, evolved

from the

dinosaurs.

JURASSIC

200140 MYA

Dinosaurs die out.

The first modern

mammals take over.

CRETACEOUS

14065 MYA

The first appearance

of many of today’s

creatures, from dogs

and cats to apes and

elephants.

TERTIARY

651.6 MYA

The first modern

human.

QUATERNARY

1.6 MYA TO PRESENT

HIP, HIP

There were two types of dinosaur,

classified by the shape of their hip

bones: bird-hipped (ornithischians),

and lizard-hipped (saurischians).

Birds actually evolved from the lizard-

hipped dinosaurs. ( p. 244.)

What is a fossil?

Paleontologists use fossils to figure out what

early life-forms would have looked like.

Most fossils form when the remains of an

animal or plant get buried in sediment

(sand or mud). Over time, the remains are

replaced by minerals in the sediment, which

keep the shape of the animal or plant.

O
 Scientists that study the history of life on

Earth are called paleontologists.

O
 The term “dinosaur” only refers to a certain

type of land-based reptile. Those that flew or

lived in the sea are not dinosaurs, but

different reptiles.

O
 There are about 700 named dinosaur species.

O

The first dinosaur fossils were Iguanodon

teeth and bones, found in England in the 1820s.

O
 The first complete dinosaur skeletons were

of 32 Iguanodons, found in a coal mine in

Belgium in 1878.

O
 The first dinosaur to be named was the

Megalosaurus, in 1824.

O

The oldest dinosaur fossils discovered to

date are 230 million years old.

FAST FACTS

Bird-hipped

Iguanodon

Lizard-hipped

T. r e x

O

Length 39 ft (12 m)

O

Time Late Cretaceous

O

Fossil location North

America

Like all life-forms,

dinosaur species have

scientific names, which

are written in Latin. The

name may reflect what

the species looked like,

or a characteristic—as

with T. r e x, one of the

largest and fiercest

meat-eating dinosaurs.

Tyrannosaurus rex

“King of the tyrant lizards”

O

Wingspan 4–8 ft

(1.2–2.5 m)

O

Time Early Jurassic

O

Fossil location Europe and

North America

Dimorphodon was not a dinosaur, but

a pterosaur—a flying reptile. It had

an enormous skull and

differently sized teeth in its

bill—large, pointed teeth at

the front, and small teeth at the back.

It ate fish, insects, and small animals,

but no one knows if it caught its prey

while flying or standing on all fours.

Dimorphodon

“Two-form tooth”

O

Length up to 11½ ft (3.5 m)

O

Time Early Permian

O

Fossil location Europe and

North America

Dimetrodon was a sail-backed

synapsid. The sail probably helped it

warm up and cool down. Synapsids

were cold-blooded

and scaly like

reptiles, but they

are actually the

ancestors of

mammals.

Dimetrodon

“Two types of teeth”

ANIMALS OF THE PAST

125

Fossil of a Pterodactylus