The Bearing of Larval Evolution on Some Problems in Frog Classification

Abstract

THE extreme specialization of the frogs (Order Salientia) and their poor early fossil record hamper our efforts to discern the principal evolutionary lines in this relatively small but seemingly inscrutable taxonomic group. From the nature and limitations of the data that have accumulated, interpretations of frog phylogeny are unavoidably conjectural, and understanding perhaps depends as heavily on one's ability to use concepts of systematics and evolution theory in general as it does on the direct evidence from the frogs. Classifications based on various combinations of extemal characters, on certain features of the skeleton and musculature, etc., have helped to clarify many problems, but none of the classifications proposed in the literature thus far are adequate by the exacting standards of modern systematics. It is increasingly apparent that major progress in frog systematics will require both more extensive and more closely integrated studies than have been customary in the past. The basic comparative anatomy and developmental morphology of the frogs need very thorough investigation, on a much broader scale than has yet been attempted. Developmental characters, in particular, are still commonly underrated and neglected as materials for the study of frog systematics, though they offer very rewarding clues to evolutionary trends and taxonomic understanding. The present paper discusses some gen