Question

The earliest known fossil tetrapod is Acanthostega, and was an aquatic animal with gills. This fossil would therefore possess?

Answer 1

The early tetrapods were the first vertebrates to truly walk on the land. Before tetrapods existed, vertebrates were all confined to living in aquatic habitats. The tetrapods began their conquest of land in the Paleozoic around 360 million years ago.

One of the earliest known tetrapods is from the genus Acanthostega. Acanthostega was aquatic; fossils show that it had gills similar to fishes. However, it also had four limbs, with the skeletal structure of limbs found in present-day tetrapods, including amphibians. Therefore, it is thought that Acanthostega lived in shallow waters and was an intermediate form between lobe-finned fishes and early, fully terrestrial tetrapods.

In 2006, researchers published news of their discovery of a fossil of a “tetrapod-like fish,” Tiktaalik roseae, that look to be an intermediate form between fishes having fins and tetrapods having limbs. Tiktaalik likely lived in a shallow water environment about 375 million years ago. The early tetrapods that moved onto land had access to new nutrient sources and relatively few predators. This led to the widespread distribution of tetrapods during the early Carboniferous period.