Reptile

 Crocodilia - Crocodilians

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 Rhynchocephalia - Tuataras

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 Squamata

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  Suborder Sauria- Lizards

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  Suborder Serpentes - Snakes

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  Suborder Amphisbaenia - Worm lizards

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Testudines - Turtles

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Superorder Dinosauria

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 Saurischia

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 Ornithischia

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The reptiles are a group of vertebrate animals. Reptiles are tetrapods, and also are amniotes (animals whose embryos are surrounded by an amniotic membrane). Today they are represented by four orders:

Related Topics:
Vertebrate - Animal - Tetrapod - Amniotes - Embryo - Membrane

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• Order Crocodilia (crocodiles and alligators): 23 species
• Order Rhynchocephalia (tuataras from New Zealand): 2 species
• Order Squamata (lizards, snakes and amphisbaenids {"worm-lizards"}): approximately 7,600 species
• Order Chelonia (turtles): approximately 300 species

Reptiles are found on every continent except for Antarctica, although their main distribution comprises the tropics and subtropics. Modern species of reptiles do not generate sufficient body heat to maintain a constant body temperature (see Leatherback Sea Turtle for an exception to this). Instead they rely on gathering and losing heat from the environment to regulate their internal temperature, such as by moving between sun and shade, or by preferential blood circulation (moving warmed blood into the body core, while pushing cool blood to the periphery). In their natural habitats, most species are adept at this, and can maintain mammalian, and even avian equivalent core body temperatures within a fairly narrow range. While this lack of internal heat imposes costs, in terms of requiring behavioral regulation, it also provides a large benefit by allowing for more efficient use of food. A reptile can survive on much less food than comparably sized mammals and birds, who burn most of their food for warmth. Most reptile species are oviparous (egg-laying). Many species of squamates, though, are capable of giving live birth. This is achieved, either through ovoviviparity (egg retention), or viviparity (babies born through no use of calcified eggs). Many of the viviparous species feed their young through various forms of placenta, just like mammals (Pianka & Vitt, 2003 pgs: 116-118).

Related Topics:
Continent - Antarctica - Tropics - Subtropics - Leatherback Sea Turtle - Oviparous - Ovoviviparity - Viviparity

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However, note the taxonomy issues described below; mammals and birds can also be viewed as descendants of reptiles.

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Reptile: Classification of reptiles ►