Origin of Tetrapod Limbs

Abstract

It is now widely understood that the more primitive Devonian lo!efins, suborder Rhipidistia of the order Crossoptcrygii, were the fishes among which the ancestors of Amphibia must be sought. No sinlgle known genus, however, will necessarily show the precise structural antecedents of the Amphibia. The Rhipidistia of which the paired fin structure is adequately known are Eusthenopteron, Sauripterus and Tristichopterus. They were fishes in form and, no doubt, in behavior. They had not begun to crawl on land. The form and functions of their fins must therefore be accounted for solely by their use as swimming appendages, not by anticipation of the tetrapod limb.