Reptiles
The reptiles are a class of vertebrates. Charateristically they are cold-blooded, have dry scaly or horny skin and a four-chambered heart. Most reptiles lay eggs with leathery shells, but a few types bear live young. Because they are cold-blooded, reptiles are more common in the tropics than in temperate regions and are not found in polar areas.
Order
Crocodiles, caimans and allies (Crocodilia)Crocodiles, caimans and their relatives - alligators and gharials - are reptiles adapted for an aquatic way of life. They are powerful swimmers, but also spend some of their time on land, basking in the sun.
Lizards, snakes and allies (Squamata)Lizards, snakes and amphisbaenids make up an order of reptiles known as the Squamata. They all have scaly skins, and all male squamates have two penises.
Turtles, terrapins and tortoises (Testudines)Turtles, terrapins and tortoises are all in one order, called the Testudines. They all have a shell, though only certain species can withdraw their lead and limbs into it.
Earth News
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About
Reptiles, or members of the class Reptilia, are air-breathing, generally "cold-blooded" (poikilothermic) amniotes whose skin is usually covered in scales or scutes. They are tetrapods (either having four limbs or being descended from four-limbed ancestors) and lay amniotic eggs, in which the embryo is surrounded by a membrane called the amnion. Modern reptiles inhabit every continent with the exception of Antarctica, and four living orders are currently recognized:
- Crocodilia (crocodiles, gavials, caimans, and alligators): 23 species
- Sphenodontia (tuataras from New Zealand): 2 species
- Squamata (lizards, snakes, and amphisbaenids ): approximately 7,900 species
- Testudines (turtles and tortoises): approximately 300 species
The majority of reptile species are oviparous (egg-laying), although certain species of squamates are capable of giving live birth. This is achieved by either ovoviviparity (egg retention) or viviparity (birth of offspring without the development of calcified eggs). Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals, with some providing initial care for their hatchlings. Extant reptiles range in size from a tiny gecko, Sphaerodactylus ariasae, that grows to only 1.6 cm (0.6 in) to the saltwater crocodile, Crocodylus porosus, that may reach 6 m in length and weigh over 1,000 kg. The science dealing with reptiles is called herpetology.
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Scientific Classification
Class: Reptile (Reptilia)
Other members of the same phylum
- Amphibians (Amphibia)
- Barnacles, copepods and allies (Maxillopoda)
- Birds (Aves)
- Cartilaginous fishes (Chondrichthyes)
- Cephalopods (Cephalopoda)
- Insects (Insecta)
- Jellyfish (Scyphozoa)
- Lobe-finned fishes and allies (Sarcopterygii)
- Lobsters, woodlice and allies (Malacostraca)
- Mammals (Mammalia)
- Millipedes (Diplopoda)
- Polychaete worms (Polychaeta)
- Ray-finned fishes (Actinopterygii)
- Sea urchins (Echinoidea)
- Spiders, mites and allies (Arachnida)
- Starfish (Asteroidea)
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