In this article we will discuss about the origin of amphibia with the help of suitable diagrams.
During the late Devonian period osteolepid fishes such as Eusthenopteron lived in the freshwater systems. It is supposed that some of these animals, first crawling from pool to pool and then spending more time on the land, gave rise to the terrestrial Amphibia.
They already possessed lungs and stoutly-constructed fins. The pace of evolution was very slow as it is known that the Devonian Amphibia, and also many of the Carboniferous Amphibia, still looked and behaved very like fishes. Nearly all of these early amphibians were wholly or largely aquatic, feeding on fish or aquatic invertebrates. The crocodile-like forms such as Eryops and small terrestrial amphibians such as Cacops were evolved not before Permian.
Earliest Amphibia:
The fossils that appear to be closest to the possible tetrapod ancestor are the osteolepids of the Lower and Middle Devonian periods about 375 million years ago. They were definitely fishes. They may have used air as well as water for obtaining oxygen, as do modern lungfishes. Elpistostege is a single Upper Devonian skull which is intermediate in proportions between such fishes and the earliest undoubted tetrapods, Ichthyostega and similar forms found in freshwater beds of Greenland. They belonged to late Devonian or early Carboniferous, about 350 million years ago.
ADVERTISEMENTS:
They are the oldest members of Labyrinthodontia having teeth with folded dentine. The enamel and dentine surrounding the pulp cavity at the base of tooth was folded into a labyrinthine pattern. They were all fish eating. This condition was also present in their crossopterygian fish ancestors.
Throughout the succeeding 100 million years of the Carboniferous and Permian periods they flourished and developed many different lines, one giving rise to the reptiles. They were mainly aquatic or semi-aquatic forms, and only a few seem to have been completely terrestrial.
The earliest labyrinthodonts were def