Reptiles

• What is a reptile?
• see also:
  • Dinosaurs

What 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 four:
  • 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 tortoises;
  • 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:
  • Ichthyosauria
    • These large marine reptiles had bodies that resembled those of present-day fish. Some species were more than 4 m (13 ft) long.
  • Sauropterygia
    • 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 Mesozoic era.
  • Pterosauria
    • 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.
  • Therapsida
    • Commonly called "mammal-like reptiles," these were not reptiles at all, but relatives of mammals that split from Reptilia by the end of the Carboniferous period.