Childrens Illustrated Encyclopedia

162

WE HAVE KNOWN ABOUT DINOSAURS for only 190 years

or so, but these great creatures roamed Earth for 160 million

years—long before humans appeared. Scientists first learned about

dinosaurs in the 1820s, when they discovered the fossilized bones

of unknown creatures. Today, these fossils show us where dinosaurs

lived, what they looked like, and what they ate. Dinosaurs were

reptiles and lived on land. Their name means “terrible lizard,”

and, like lizards, many of them had tough, scaly skin. There were

hundreds of different kinds of dinosaurs, divided into two main

groups. The ornithischians (bird-hipped dinosaurs), such as Protoceratops, had

hipbones similar to birds; the saurischians (lizard-hipped dinosaurs), such as

Diplodocus, had hipbones similar to lizards. Not all dinosaurs were giants—

Compsognathus was the size of a chicken and Heterodontosaurus was the size

of a large dog. Some dinosaurs, such as Tyrannosaurus rex, were carnivores

(meat eaters); others, such as Stegosaurus, were herbivores (plant eaters).

About 66 million years ago, dinosaurs and the swimming and flying

reptiles that lived at the same time died out.

The reason for this is still uncertain.

REPTILES

Dinosaurs 162-

reptiles, like crocodiles, alligators,

and the lizard shown above. Like

other reptiles, dinosaurs had scaly

skin and laid eggs. Unlike lizards

and other reptiles, dinosaurs had

long legs, so they could move

faster on land.

Jaw bone of a Gorgosaurus

DINOSAURS

162

Carnivorous

dinosaurs often

had large, strong

claws for grabbing

their prey. The claw

shown here belonged

to Baryonyx, which is

nicknamed “Claws.”

Ornithocheirus was a

fishing pterosaur—it

swept low over the

water and caught

fish in its beak.

GORGOSAURUS

Carnivorous dinosaurs, such as

the Gorgosaurus, had huge teeth

and powerful jaw muscles for a

strong bite. Not all dinosaur teeth

were this large, though; some

were as small as human teeth.

When dinosaurs lived on

the land, flying reptiles called

pterosaurs flew in the air, and

reptiles called ichthyosaurs and

plesiosaurs swam in the sea.

Tyrannosaurus
had tiny hands
that did not
reach its mouth.
We do not know
what the hands
were used for.

TYRANNOSAURUS REX

The gigantic Tyrannosaurus,

discovered in North America,
was one of the largest carnivorous

(meat-eating) dinosaurs.
Tyrannosaurus measured 39 ft

(12 m) in length and stood 13 ft
(4 m) high. Its massive teeth were

more than 6 in (15 cm) long.
Tyrannosaurus weighed almost

7 tons, but it could still run and
hunt other dinosaurs. Bite

marks on fossils show us that
Tyrannosaurus attacked giant

dinosaurs like Triceratops.

A lizard-type

pelvis

Tyrannosaurus rex belonged

to the group of lizard-

hipped dinosaurs called

Saurischians.