Page 61 - Reptiles & Dinosaurs (Britannica Illustrated Science Library)

56 LIZARDS AND CROCODILES REPTILES AND DINOSAURS 57

Venerated and Feared ALLIGATOR

CLAWS Alligatoridae
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
C 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 the mouth is Number of Types Eight
Diet
closed.
Insects, Mammals, Birds
sun themselves or rest in the water. However, they can also swim,
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.
Alligators
SCALES
and Caimans
GAVIAL
Gavialis GAVIAL Alligators and caimans are almost completely limited
gangeticus has a long, narrow to freshwater. They make their nests by piling up
snout, with long
front teeth. grass, dirt, and leaves to lay their hard-shelled eggs.
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 The female often helps her eggs to hatch by putting
CROCODILE
Degree of Danger Harmless has a V-shaped them in her mouth, where she rolls them against her
snout, narrower JOINT palate with her tongue until they crack.
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 TEETH How They Move Habitat Freshwater and Saltwater
long, narrow snout with small, sharp 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
The fourth tooth on the
interlocked, outward-curving teeth are movement is swimming or crawling, lower jaw is visible when Life Span 70 years
perfect for catching slippery fish. SNOUT crocodiles can run for short distances if the mouth is closed.
Adult males drive away their rivals Long, narrow they feel threatened. They can reach
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 its four limbs. 30º

The front legs
Its legs are begin the
2 suspended. movement. 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
The cycle legs come into miles They are distinguished by their great
3 starts over. action. 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 IS THE SPEED THEY CAN SWIMMING without drowning. They make their nests in holes on the beach. The
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.