The Origin of the Amphibia

Abstract

The origin of land vertebrates is a constant subject of discussion. Recent findings in zoology and paleontology (Latimeria, Ichthvostega, Hesperoherpeton, etc.) have supplied many new arguments, but the results arrived at by various authorities show considerable differences. The author is convinced, however, that present knowledge concerning the evolution of tetrapody can be arranged in a harmonious picture. This is the aim of the review. It is concluded that all the evidence speaks in favor of a monophyletic origin of land vertebrates. Among them, the important differences between amphibians on the one side and the reptiles and their descendants on the other are emphasized. The probably sequence with which the various tetrapod features have accumulated, the reasons which prevented the emergence of terrestrial forms from being ever repeated, and the evolution of the amphibian ontogeny are discussed.