Updated by: Arabinda Naik
The class Reptilia includes about 9500 species that animals like lizard, snakes, turtles, tortoise, crocodiles, etc. They dominated the earth about 200 million years ago in the Jurassic period of Mesozoic era called the golden age of reptiles. They are terrestrial, a few of them live in water, such as tortoise, crocodile etc. the body may be long, cylindrical, or short and broad. It is divisible as head, neck, trunk, and tail. They have dry, rough, and non-glandular skin. It is provided with horny, epidermal scales. Appendages pentadactyl limbs with powerful horny claws. limbs are locomotory organs. Endoskeleton is bony. Skull is monoconidylic for articulation with the vertebral column. Digestive system is well developed. The mouth is large with acrodont teeth in both the jaws. Jaw bones are movable to swallow large prey. Lungs are respiratory organs. Ribs help expand and contract body cavity making the lungs more efficient. Turtles show cloacal respiration. Heart is usually three-chambered with two auricles and one ventricle. The ventricle is incompletely divided by a septum. The heart is four chambered in crocodiles. RBCs are oval, biconvex, and nucleated. Excretion occurs through kidneys. The landforms release uric acid. while aquatic forms excrete urea. Nervous system contains 12 pairs of cranial nerves. Sense organs like eyes, ears and nose are well developed. Reptiles are cold blooded (poikilothermic) animals They hibernate in winter. Snakes and Tigands shed their scales as. skin cast. These are unisexual and show sexual dimorphism. fertilisation is internal. Most reptile are oviparous and some ovoviviparous such as viper sea snakes. The eggs are retained inside the body of the mother and growing embryos derive shelter and nourishment from the mother development is direct. e.g., Calotes (garden lizard). Draco (flying lizard). Chameleon (arboreal lizard), Hemidactylus (wall lizard). Crocodilus (crocodile), Alligator (alligator), Sphenodon (tuatara-the living fossil). Naja (cobra), Bungarus (krait). Vipera (viper).