is a reptile?
- REPTILE, common name for any animal of the
vertebrate class Reptilia.
- Millions of years ago, during the Mesozoic era, dinosaurs,
pterosaurs (flying reptiles) and other reptiles were the
most numerous vertebrate animals on the earth. Reptiles
have since been reduced from 17 recognized orders to just
- Squamata, with about 3000
species of lizards, 2500 of snakes, and 140 of
worm lizards (amphisbaenians);
- Chelonia, or Testudines,
comprised of about 250 species of turtles and
- Crocodylia, including 21 species
of crocodiles, alligators, gavials, and caimans;
- Rhynchocephalia, which
flourished during the Jurassic period but today
is represented only by the tuatara, which lives
on several islands off the coast of New Zealand.
- Like most classes of vertebrates (animals that have a
backbone), reptiles vary in size. The increasingly rare
Indian gavial may reach a length of 9 m (30 ft) and weigh
540 kg (1200 lb). The gecko lizard, by contrast, is
typically 3 cm (1.2 in) long. Reptiles also include a
fascinating range in behavior and appearance; yet, from
the timid box turtle to the savage Komodo dragon, all
share certain traits that set them apart as reptiles.
- The earliest reptiles developed from amphibians during
the Upper Carboniferous period of the Paleozoic era about
300 million years ago. Many forms evolved and flourished
in the Mesozoic era,
the Age of Reptiles.
- The best-known orders of extinct reptiles
are as follows:
- These large marine reptiles had bodies
that resembled those of present-day fish.
Some species were more than 4 m (13 ft)
- This order included long-necked aquatic
forms that had large bodies and limbs
adapted for moving through the water.
- Saurischia and Ornithischia
- These orders included the reptiles
commonly known as dinosaurs.
First found in Triassic strata, they
became extinct at the close of the
- This large, diverse group of flying
reptiles is related to the dinosaurs.
Their wings were thin membranes attached
to the body by the very long fourth
finger of each arm.
- Commonly called "mammal-like
reptiles," these were not reptiles
at all, but relatives of mammals that
split from Reptilia by the end of the