Reptiles are found in a small class of cold-blooded animals that are divided
into four living orders (approx. 16 other orders are extinct). Reptiles are
found throughout the entire world, from the steaming deserts to the inner
city to hundreds of feet below the ocean. They are absent from the polar
regions and mountain peaks. Reptiles share many common traits: they are
all cold-blooded (meaning they can't regulate their body temperature); they
have skin covered in scales or scutes (patches of bony or horny skin); the
legs are short or entirely absent; and most are oviparous (they lay eggs),
although some are ovoviviparous (eggs are kept in the mother's belly until
they hatch). The egg yolk is rick and the shell is strong. Incubation is
caused by the warmth of the ground, whether the eggs are laid in a nest
(alligators) or buried (sea turtles). There is no larval stage with reptiles,
unlike with amphibians. Also, the eggs are leathery instead of jelly-encased.
There are 5000-6000 species of reptiles in four orders and three subclasses:
Subclass Lepidosauria
Subclass Anapsida
Subclass Archosauria
Rhynchocephalia (tuataras)
Squamata (lizards, snakes, amphisbaenas)
Suborder Sauria (lizards)
Suborder Serpentes (snakes)
Suborder Amphisbaenia (amphisbaenas)
Testudines or Chelonia (turtles, tortoises, terrapins)
Crocodylia (crocodiles, alligators, caimans, gavials, false gavials)
Back