Britannica Illustrated Science Library: Reptiles and Dinosaurs by Encyclopedia Britannica

Author:Encyclopedia Britannica [Britannica, Encyclopedia]
Language: eng
Format: epub
Published: 2011-10-29T23:50:25+00:00

56 LIZARDS AND CROCODILES

REPTILES AND DINOSAURS 57

ALLIGATOR

Venerated and Feared

Alligatoridae

CLAWS

C rocodiles—along with their relatives, the alligators, caimans, and gavials—are very ancient animals. They belong to the same group that included the LOWER JAW

The lower

dinosaurs and have changed very little in the last 65 million years.

teeth are

Habitat

Freshwater

invisible when

They can go for long periods without moving; during these times, they Number of Types Eight

the mouth is

Diet

Insects, Mammals, Birds

sun themselves or rest in the water. However, they can also swim, closed.

jump, and even run at high speed to attack with force and precision. In spite of their ferocity, female crocodiles provide more care for their young than any other living group of reptiles.

10 to 20 feet (3-6 m)

SCALES

are flat on

the tail.

SCALES

Alligators

GAVIAL

and Caimans

GAVIAL

Gavialis

Alligators and caimans are almost completely limited has a long, narrow

gangeticus

to freshwater. They make their nests by piling up snout, with long

grass, dirt, and leaves to lay their hard-shelled eggs.

front teeth.

The female often remains near the nest to keep would-be thieves from invading. Although they look Habitat

Freshwater

clumsy, alligators can use their jaws with precision.

Number of Types

One

CROCODILE

The female often helps her eggs to hatch by putting Degree of Danger

Harmless

them in her mouth, where she rolls them against her has a V-shaped

JOINT

palate with her tongue until they crack.

snout, narrower

than the alligator's.

13-23 feet (4-7 m)

ALLIGATOR

NILE

has a wide, short,

CROCODILE

U-shaped nose.

Crocodylos

The Gavial

niloticus

is the strangest of all crocodiles. Its

How They Move

long, narrow snout with small, sharp

TEETH

Habitat

Freshwater and Saltwater

are longest

TEETH

teeth sweeps through the water. Its

in front.

Although their preferred form of

number from 64 to 68.

Number of Types One

interlocked, outward-curving teeth are

movement is swimming or crawling,

The fourth tooth on the

lower jaw is visible when

Life Span

70 years

perfect for catching slippery fish.

crocodiles can run for short distances if

SNOUT

the mouth is closed.

Adult males drive away their rivals

they feel threatened. They can reach

Long, narrow

with loud buzzing sounds that they

nose

speeds of up to 9 miles per hour (15 km/h)

make by exhaling air

when running, with their abdomens

through a bump on

supported above their knees and their

their noses.

elbows slightly bent. They can go even

16 to 20 feet (5-6 m)

faster when sliding on mud.

It moves forward with

1

30º

its four limbs.

The front legs

begin the

Its legs are

2

movement.

suspended.

POSTURE

Semi-crouched. The knees and elbows

are slightly bent.

Crocodiles

have four feet. In this way,

they are very similar to lizards.

Then the hind

legs come into

They are distinguished by their great

The cycle

miles

3

action.

starts over.

size and ferocity. Several rows of bony

9 per hour

plates that look like spines or teeth run down the length of their back. They can stay in the water for long (15 km/h)

periods of time, and they are able to swallow underwater The tail is

raised to avoid

SWIMMING

without drowning. They make their nests in holes on the beach. The IS THE SPEED THEY CAN

acting as a

Using its tail for locomotion, it moves with

Johnston's, or freshwater, crocodile, of tropical northern Australia, can brake.

REACH AT A FULL RUN.

agility through the water.

gallop to the water by raising all four feet off the ground.

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