Snakes are elongate, legless,
carnivorous reptiles of the suborder Serpentes that can be distinguished from
legless lizards by their lack of eyelids and external ears. Like all
squamates, snakes are
ectothermic,
amniote vertebrates covered in overlapping
scales. Many species of snakes have
skulls with many more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their
highly mobile jaws. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional
lung. Some species retain a
pelvic girdle with a pair of
vestigial claws on either side of the
cloaca.
Living snakes are found on every continent except Antarctica and on most islands. Fifteen
families are currently recognized, comprising 456
genera and over 2,900
species.
[1][2] They range in size from the tiny, 10 cm-long
thread snake to
pythons and
anacondas of up to 7.6 metres (25 ft) in length. The recently discovered fossil
Titanoboa was 15 metres (49 ft) long. Snakes are thought to have evolved from either burrowing or aquatic lizards during the
Cretaceous period (
c 150
Ma). The diversity of modern snakes appeared during the
Paleocene period (
c 66 to 56 Ma).
Most species are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom potent enough to cause painful injury or
death to humans. Nonvenomous snakes either swallow prey alive or kill by
constrictionSnakes are elongate, legless,
carnivorous reptiles of the suborder Serpentes that can be distinguished from
legless lizards by their lack of eyelids and external ears. Like all
squamates, snakes are
ectothermic,
amniote vertebrates covered in overlapping
scales. Many species of snakes have
skulls with many more joints than their lizard ancestors, enabling them to swallow prey much larger than their heads with their
highly mobile jaws. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional
lung. Some species retain a
pelvic girdle with a pair of
vestigial claws on either side of the
cloaca.
Living snakes are found on every continent except Antarctica and on most islands. Fifteen
families are currently recognized, comprising 456
genera and over 2,900
species.
[1][2] They range in size from the tiny, 10 cm-long
thread snake to
pythons and
anacondas of up to 7.6 metres (25 ft) in length. The recently discovered fossil
Titanoboa was 15 metres (49 ft) long. Snakes are thought to have evolved from either burrowing or aquatic lizards during the
Cretaceous period (
c 150
Ma). The diversity of modern snakes appeared during the
Paleocene period (
c 66 to 56 Ma).
Most species are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom potent enough to cause painful injury or
death to humans. Nonvenomous snakes either swallow prey alive or kill by
constriction