Characteristics Of Reptiles

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A reptile is an ectothermic vertebrate that lugs and scaly skin.
Reptiles have tough, dry, scaly skin offering protection against desiccation and physical injury. The skin consists of a thin epidermis, shed 3'l periodically, and a much thicker, well-developed dermis (Figure 3a). The dermis is provided with chromatophores, the colour-bearing cells that give many lizards and snakes their colourful patterns. The characteristic scales of reptiles are formed largely of keratin. Scales are derived mostly from the epidermis; they are not homologous to fish scales, which are bony, dermal structures. In some reptiles, such as alligators, the scales remain throughout life, growing gradually to replace wear. In others, such as snakes and lizards, new scales grow beneath the old, which are shed at intervals. Turtles add new layers of keratin under the old layers of the platelike scutes, which are modified scales. In snakes the old skin (epidermis and scales) is turned inside out when discarded; lizards split out of the old skin leaving it mostly intact and right side out or it may slough off in pieces.
All reptiles, except the limbless members, have better body support than the amphibians and more efficient.
The reptilian nervous system is considerably more complex than the amphibian system. Although the reptile's brain is small, the cerebrum is larger relative to the rest of the brain. Connections to the central nervous ( system are more advanced, permitting complex kinds of behaviour unknown in amphibians. ly designed limbs for travel on land.
Reptiles are air-breathing, cold-blooded vertebrates that have scaly bodies as opposed to hair or feathers; they represent an intermediate position in evolutionary development between amphibians and warm-blooded vertebrates, the birds and mammals. They are tetrapods and amniotes whose embryos are surrounded by an amniotic membrane, and members of the class Sauropsida inhabiting every continent with the exception of Antarctica. Today they are represented by four orders!
Today there are 6,800 reptile species on earth; the major groups are alligators and crocodiles, turtles, lizards, and snakes. All reptiles are cold-blooded, which is why they warm themselves in the sun, and have bodies covered in dry, horny scales. Some reptiles lay eggs; others give birth to live young.

Refernce'' www.botany.unp.ac.za/notes/chsr,htm
[taxes book] Prentice Hall Science Explorer page100