EVERYDAY SCIENCE

Detailed explanation-1: -The earliest vertebrates were the hagfish and other fishes which lived in water. With evolution, the Amphibians evolved from the jawless fishes and could survive on land (as they had lungs). Therefore, amphibians are considered the first terrestrial vertebrates.

Detailed explanation-2: -The earliest well-known amphibian, Ichthyostega, was found in Late Devonian deposits in Greenland, dating back about 363 million years. The earliest amphibian discovered to date is Elginerpeton, found in Late Devonian rocks of Scotland dating to approximately 368 million years ago.

Detailed explanation-3: -The earliest known fossil vertebrates were heavily armored fish discovered in rocks from the Ordovician Period about 500 to 430 Ma (megaannum, million years ago).

Detailed explanation-4: -The most complete skeletal material of an early amphibian tetrapod is the Ichthyostega, found in Greenland and dated 362 million years old. The earliest amphibian fossils are poorly preserved 370-million-year-old limb bones from Scotland.