Amphibia Split Surfaces

From: CNAH <jcollins@ku.edu> Subject: Amphibia Split Surfaces To: Date: Friday, May 23, 2008, 8:47 AM NEWS RELEASE The Center for North American Herpetology Lawrence, Kansas http://www.cnah.org 23 May 2008 A STEM BATRACHIAN FROM THE EARLY PERMIAN OF TEXAS AND THE ORIGIN OF FROGS AND SALAMANDERS Jason S. Anderson, Robert R. Reisz, Diane Scott, Nadia B. Fröbisch & Stuart S. Sumida Nature 453: 515-518 (22 May 2008) Abstract: The origin of extant amphibians (Lissamphibia: frogs, salamanders and caecilians) is one of the most controversial questions in vertebrate evolution, owing to large morphological and temporal gaps in the fossil record. Current discussions focus on three competing hypotheses: a monophyletic origin within either Temnospondyli or Lepospondyli, or a polyphyletic origin with frogs and salamanders arising among temnospondyls and caecilians among the lepospondyls. Recent molecular analyses are also controversial, with estimations for the batrachian (frog– salamander) divergence significantly older than the palaeontological evidence supports. Here we report the discovery of an amphibamid temnospondyl from the Early Permian of Texas that bridges the gap between other Palaeozoic amphibians and the earliest known salientians and caudatans from the Mesozoic. The presence of a mosaic of salientian and caudatan characters in this small fossil makes it a key taxon close to the batrachian (frog and salamander) divergence. Phylogenetic analysis suggests that the batrachian divergence occurred in the Middle Permian, rather than the late Carboniferous as recently estimated using molecular clocks, but the divergence with caecilians corresponds to the deep split between temnospondyls and lepospondyls, which is congruent with the molecular estimates. ***** A gratis PDF of this article about the Class Amphibia is available from the CNAH PDF Library at http://www.cnah.org/cnah_pdf.asp