Amphibians

Abstract

The Amphibia were the dominant land vertebrates in the Carboniferous and were certainly the stock from which the reptiles and in turn the mammals and birds evolved. Like all new groups entering a virtually untenanted environment they underwent adaptive radiation and occupied different habitats within the limits imposed by their general structure and physiology. The body in most was rather crocodile-like with bony scales along the belly and in some cases on other parts as well. The skull was large and heavy, being completely roofed by bone. The limbs were short and the girdles massive for the attachment of leg muscles and the support of the body weight. The tail was long. Some were very large up to 3 m or more with others no more than about 10 cm in length. They were abundant and in great variety in tropical swamps and coal forests and uniformly carnivorous as far as we know, as indeed are the modern amphibians. Some became mainly terrestrial while others returned to water and were purely aquatic with an eel-like body and limbs reduced. Amphibians are the only tetrapods with a larva which metamorphoses to the adult and there is little doubt that the earliest amphibians, in spite of the great size of some, also began life as a tadpole.