Page 75 - Reptiles & Dinosaurs (Britannica Illustrated Science Library)

70 TURTLES AND SNAKES REPTILES AND DINOSAURS 71

Internal COLD-BLOODED HEART LIVER IDENTIFICATION OF SOME POISONOUS TAIL “Blind” Snakes
The ventricle has an
Their temperature varies according to
Suddenly
AND NONPOISONOUS VIPERS
the environment. They do not generate
rattle) but does
their own body heat. incomplete partition. is long and located narrows (like a Some subtropical and tropical
along the esophagus.
snake species live underground
ESOPHAGUS
Structure LUNG BLADDER POISONOUS BODY and only come out in droughts or
not end in a point
floods. These are the smallest
HEAD Typically
STOMACH wide and triangular Relatively long snakes; some are no longer than 4
and rough inches (10 cm). They have large
nakes are scaly reptiles with long SPLEEN SCALES heads, few teeth, and bodies
bodies and no legs. Some are are generally NONPOISONOUS covered in very soft, slippery
S poisonous, but others are not. Like found in the HEAD Typically narrow; hard scales, which enable them to slide
into anthills and termite hills,
dorsal region.
all reptiles, they have a spinal column and to distinguish from the neck BODY TAIL their only sources of food. Their
Narrows
Narrow, with
eyes, which are covered with
a skeletal structure composed of a system of smooth scales gradually and scales, barely work.
ends in a point
vertebrae. The anatomical differences between
species reveal information about their habitats and diets—climbing
snakes are long and thin, burrowing snakes are shorter and
thicker, and sea snakes have flat tails that they use as fins.
LARGE
EMERALD INTESTINE
TREE BOA
Corallus caninus

SMALL
TREE BRANCH INTESTINE TYPES OF MOVEMENT DEPENDING ON HABITAT
Boas can change color to is divided into a
imitate the branch they small tract and a
are curled around. large tract, which
Primitive THE SPINAL COLUMN ends well before RECTILINEAR SIDEWINDING
the tip of the tail.
Snakes is composed of an assembly of jointed Rainbow Boa Desert Snakes
Boas and pythons were the first 33 feet vertebrae with prolongations that SKIN
protect the nerves and arteries. The
snake species to appear on Earth. system makes them enormously flexible. Many species of
Many have claws or spurs as snake have no scales
vestiges of ancient limbs of their (10 m) on the underside. SERPENTINE CONCERTINA
ancestors. They are not poisonous, VERTEBRAE King Cobra Rattlesnake
but they are the largest and LENGTH OF A PYTHON Neural arch
strongest snakes. They live in trees, OVARIES
and some, such as the anaconda—a The female Sophisticated Snakes
South American boa—live in rivers. Body of the reproductive
Spotted Python vertebra organs Snakes of the family Viperidae, as well as other
Antaresia maculosa poisonous snakes that appeared later, have highly
inhabits the forests acute senses and a mouth apparatus
of Australia. Hemal INFRARED PITS with a system of retractable
keel
Snakes of the family Viperidae fangs for injecting
are distinguished by two venom.
thermoreceptive pits on either
FLOATING RIBS side of their heads, which
allow the body to Vertebra enable them to sense
increase in size. differences in temperature.
Some pits are extremely
Floating sensitive, helping the snake
rib to gauge the size of its
Range of prey when it hunts
motion of
the ribs at night.
REPRODUCTION
is sexual, and most 2,978
400 vertebrae THE NUMBER A species lay eggs. Some SNAKE SPECIES EXIST. GABOON VIPER
species give birth to
Bitis gabonica
live young.
SNAKE CAN HAVE