Reptile

Reptile

Reptiles are a group of vertebrates comprising today's turtles, crocodilians, snakes, amphisbaenians, lizards, tuatara, and their extinct relatives. The study of these traditional reptile orders, historically combined with that of modern amphibians, is called herpetology.

Characteristics

Because they are defined paraphyletically, not all reptiles are closely related. They do share some morphological and physiological characteristics.

Cold-bloodedness

The majority of reptile species are ectothermic, which means that their internal body temperature depends on the ambient environment temperature.

Scales

Reptiles are known for their scales. Reptile scales vary in size, shape, and texture, and are typically keratinous, but there are some exceptions, such as the scales of turtles and crocodiles.

Heart

The heart has two atria and one ventricle. The ventricle is incompletely separated into two by a wall, giving the reptile heart a unique structure.

Classification

Reptiles are classified into four orders:

• Testudines: Turtles
• Squamata: Lizards, snakes and amphisbaenians
• Crocodilia: Crocodiles, gavials, caimans, and alligators
• Rhynchocephalia: Tuatara

Evolution

Reptiles first appear in the fossil record 315 million years ago and were the dominant animals during the Mesozoic era, which lasted for 270 million years until the extinction of the dinosaurs.

See also

• List of reptiles
• Reptile scale
• Reptile reproduction
• Reptile development

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