ABSTRACT

The word 'amphibia' is Latin in origin. It means double life, thus amphibians are animals that either move back and forth in water and land, or live one stage of their lives in water and another on land. They are tetrapods and are believed to have evolved roughly 250 million years ago from ancient sarcopterygians. The first amphibian is not known, but the structure of limbs, skulls and teeth suggests that Ichthyostega is probably similar to the earliest amphibians. The class Amphibia includes all animals that possess skin with mucoid secretions. They lack epidermal scales, feathers or hair and their larvae are usually aquatic and undergo metamorphosis to the adult (Miller and Harley, 2002).The orders found under class Amphibia include; order Caudata, Gymnophiona, and Anura. Order caudata include amphibians that possess long tail, two pairs of limbs, lack middle ear; examples include salamanders and newts. Order gymnophonia includes the caecilians which are elongate, limbless, segmented, by annular grooves, have specialized structures for burrowing and short and pointed tail. The anurans (salientia) include the frogs and toads which are tailless, have elongated hind limbs modified for jumping and swimming; five to nine presacral vertebrae fused into rodlike urostyle; tympanum and larynx well developed. Amphibians occur on all continents except Antarctica (Miller and Harley, 2002).