Amphibians and Reptiles (Important Facts) {Part-13}

THE EARLIEST KNOWS AMPHIBIANS, such as Acanthostega and Ichthyostega, lived about 363 million years ago at the end of the Devonian period (409-363 million years ago).

Fossil Skull of Acanthostega

Model of Ichthyostega

Their limbs may have evolved from the muscular fins of lungfish-like creatures. These fish can use their fins to push themselves along the bottom of lakes and some can breathe at the water's surface. While amphibiains exist on land, they are dependent on a wet environment because their skin does not retain moisture and most and most species must retain to the water to lay their eggs.

Skeleton of Eryops

 Evolving from amphibians, reptiles first appeared during the Carboniferous period (363-290 million years ago):  Westlothiana  a possible early reptile, lived on land 338 million years ago. The development of the amniotic egg, with an embryo enclosed in its own wet environment (the amnion) and protected by a waterproof shell, freed reptiles from the amphibian's dependence on a wet habitat. A scary skin protected the reptile from desiccation on land and enabled it to exploit ways of life closed to its amphibian ancestors. Reptiles include the dinosaurs, which came to dominate life on land during the Mesozoic era (245-65 million years ago).