Evolution of the Dinosaurs

Dinosaur Ancestors

What were some of the earliest species that led to amphibians?

Several fossils of pre-amphibian species have been uncovered. For example, one of the earliest known steps to amphibians is the Acanthostega, which evolved about 360 million years ago during late Devonian. It was one of the first to have feet; it also had toes (eight per limb), no fin rays, a large, load-bearing pelvis, and may have retained its gills into adulthood. Another early amphibian fossil is an intermediate between fish and amphibian: the Ichthyostega, with the best fossils having been uncovered in Greenland. This early amphibian lived in the swamps of the Late Devonian period, enjoying mild, warm climates. By this time, too, insects had evolved on land, providing food for the slow-moving amphibian. The Ichthyostega was a three-foot-(one-meter-) long animal with four limbs and a fin on its tail—a combination of amphibian and fish features that allowed it to swim and to climb on land.


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