CLASS REPTILIA (Creeping Vertebrates)Reptilia represents first class of vertebrates that fully adapted for life in dry places or land.
- Predominantly terrestrial, creeping or burrowing, mostly carnivorous, air-breathing, cold-blooded, oviparous and tetrapod vertebrates.
- Body bilaterally symmetrical and divisible into four regions-head, neck, trunk and tail.
- Limbs 2 pairs, pentadactyl. Digits provided with horny claws. However, limbs absent in a few lizards and all snakes Exoskeleton of horny epidermal scales, shields, plates and scutes. Skin dry, cornified and devoid of glands.
- Mouth terminal. Jaws bear simple conical teeth. In turtles teeth replaced by horny beaks.
- Endoskeleton bony. Skull with one occipital condyle (monocondylic skull). A characteristic T-shaped interclavicle present.
- oval and nucleated. Cold-blooded. Respiration by lungs throughou.
- Kidneys are metanephric. Crocodiles are ammonotelic, turtles and alligators are ureotelic, lizards and snakes are uricotelic
- Brain with better development of cerebrum than in Amphibia. Cranial nerves 12 pairs.
- Lateral line system absent. Jacobson's organs present in the roof of mouth. Sexes separate. Male usually with muscularcopulatory organ.
- Fertilisation internal. Mostly oviparous. Large yolky meroblastic eggs, covered with leathery shells, always laid on land.
- Embryonic membranes (amnion, chorion, yolk sac and allantois) appear during development. No metamorphosis. Young resemble adults.
- Parental care usually and really absent.
