Acanthostega had a tail like a fish and gills for breathing in water. But it had the legs and feet of a land animal. The worlds first reptiles appeared around 300 million years ago. These animals evolved from an older group named amphibians. The word amphibian means double life and describes those that live on land and water.
Reconstruction of pedes of various taxa. Pederpes, Greererpeton, Silvanerpeton and Proterogyrinus show asymmetrical metatarsals (see arrows) compared with those of the Devonian forms Acanthostega, Ichthyostega and Tulerpeton. In Acanthostega and Ichthyostega, the metatarsals are not clearly differentiated, and in Tulerpeton, if correctly interpreted, they are cylindrical but include some interarticulations. Scale bars, 10 mm. After reference (2)