The rhipidistian - amphibian transition

Abstract

The transition from the rhipidistian crossopterygian fishes to the amphibians involved many changes in morphology, physiology and behavior. The selection pressures promoting terrestrial adaptations and concurrently preserving the aquatic ones must have been responsible for extensive experimentation during the transitional interval. A multiple origin of the amphibian level is therefore regarded as probable, and this view is supported by the diversity of the earliest known amphibian groups. © 1965 by the American Society of Zoologists.