EUSTHENOPTERON

genus of extinct fishes preserved as fossils in rocks of late Devonian age (the Devonian Period lasted from 408 to 360 million years ago). Eusthenopteron was a member of the group known as the Crossopterygii, or lobe-finned fishes; it was probably near the main line of evolution leading to the first terrestrial vertebrates, the primitive amphibians. It was a slender fish growing to 1.5 to 1.8 metres (5 to 6 feet), and was an active carnivore. In many of its anatomical characteristics, Eusthenopteron foreshadows the early amphibians. The overall pattern of the skull bones is similar to that of early amphibians, but the vertebral column had features intermediate between a fishlike column and that of an amphibian. The paired fins were clearly of the type antecedent to terrestrial vertebrate limbs. Eusthenopteron had lungs and could probably make brief excursions out of the streams and ponds in which it lived.