A stem batrachian from the Early Permian of Texas and the origin of frogs and salamanders

The origin of the amphibians (frogs, salamanders and caecilians) is one of the most controversial questions in vertebrate evolution, because of the large morphological and temporal gaps between today's amphibians and the extinct fossil forms. The discovery of an unusually complete Palaeozoic amphibian from the Early Permian of Texas has now helped to fill that gap. The new fossil has the overall appearance of a temnospondyl — an archaic amphibian — but boasts many characteristic features seen in modern frogs, toads and salamanders. A phylogenetic analysis splits the modern amphibia into two groups, separating at some time before 330 million years ago, with frogs, toads and salamanders related to temnospondyls, and caecilians more closely related to the lepospondyls, another group of archaic amphibians.