For a long time, amphibians were co

For a long time, amphibians were confused with reptiles. Like reptiles, they have three-chambered hearts and are cold-blooded. Some amphibians, such as salamanders, are even shaped like lizards.However, unlike reptiles, amphibians never have claws on their toes or scaleson their bodies.Furthermore, the eggs of amphibians lack shells, so they must be laid in water or in moist places.Amphibians were the first creatures to spend sizable amounts of their lives on land.The larvae of most amphibians, such as frog tadpoles, are born with gills and live in water. However,their gills disappear as they develop lungs. Most retain the ability to breathe through the moist surface of their skin. This comes in handy when they hibernate in the bottom mud of lakes and ponds during the coldest months. They take in the small amount of oxygen they need through their skin. Some amphibians undergo what is known as a “double metamorphosis”, changing not only from gill breathers to lung breathers but also from vegetarians to insectivores.Although the amphibian class is rather small in number of species, it shows great diversity. There aret hree major types. The caecilians of the tropics are long, legless, burrowing creatures. Caudate amphibians, such as newts and salamanders, mostly have long tails and stubby legs.Salientians, which include both frogs and toads, are tailless as adults and have powerful hind legs.Toads differ from frogs primarily in that they have dry, warty skin