© 1992 by The Society for Integrative and Comparative Biology
Recent Progress in Understanding Early Tetrapods1
Department of Organismal Biology and Anatomy, University of Chicago Chicago, Illinois 60643
Department of Biology, California State University San Bernardino San Bernardino, California 92407
This paper reviews significant discoveries and interpretations made for Paleozoic tetrapods over the past twenty-five years. In that span twelve significant, new localities have been found, including the oldest ever at about 370 million years in age. About 60 new genera have been described; five providing important insight into the early evolution of land vertebrates. The number of exceptionally well known taxa with multiple, excellently preserved specimens has doubled to eight from four. The very earliest tetrapods have been discovered to have been polydactylous, the ear region to have had a complicated early evolution and the specialized tooth type found in Recent amphibians has been found in a group of Lower Permian temnospondyl amphibians, indicating an evolutionary relationship. Perhaps the most significant advance in understanding the evolution of early tetrapods is that the basal amniote groups have become better characterized and a start has been made in providing a defensible hypothesis for their relationships. The ascendancy of cladistics, functional morphology and plate tectonics has changed the way paleontologists view fossils resulting in more defensible phylogenies and behavioral and biogeographical scenarios. These approaches to understanding have, perhaps, had a more profound impact than any of the new fossil discoveries.