Reptile Characteristics

Characteristic

Description

Circulatory System	Nearly all reptiles have three-chambered hearts; the exceptions are crocodilians, which have four-chambered hearts.
Respiration	All reptiles breathe with lungs, and unlike amphibians, reptiles never pass through an embryonic stage involving gills.
Skeletal Features	All reptiles have backbones or spinal columns. Except for snakes, reptiles have paired limbs that typically end in five-clawed fingers or toes. Most reptiles have a pelvis that is associated with at least two spinal bones.
Reproduction	Most reptiles reproduce by laying eggs, although some give birth to live young that have hatched from eggs inside the mother's body. Most reptiles produce amniote eggs, which are able to survive outside of water. These eggs have complex membrane systems and protective shells that are permeable to oxygen and other gases.
Temperature Regulation	Reptiles are cold-blooded, meaning that the internal temperature of their bodies varies, depending on the environment.
Skin	Reptiles have tough, dry skin covered with scales that serves as a barrier to moisture and prevents water from leaving the body.
Sense Organs	With the exception of blind snakes, reptiles rely more heavily on vision than on any other sense to detect objects in their surroundings. Most reptiles lack external ears and instead have an eardrum that is positioned near the eyes, close to the surface of the skin.
Development	Reptiles possess most of their adult characteristics at the time of hatching. Unlike most amphibians, they do not undergo a larval stage or experience metamorphosis.