The origin of modern amphibians: a re-evaluation

Abstract

There are currently three competing hypotheses seeking to explain the evolutionary origins of modern amphibians. The lepospondyl hypothesis holds that the lysorophian lepospondyls constitute the sister taxon to all lissamphibians. The temnospondyl hypothesis suggests that modern amphibians are most closely related to the dissorophoid temnospondyls. Finally, the polyphyletic hypothesis posits that the modern amphibian orders have separate evolutionary origins from among different groups of Palaeozoic tetrapods. Here, we review the character matrices used in previous studies. These data sets differ significantly in choice of characters. Therefore, we built a matrix based on data from all three hypotheses and analysed key taxa phylogenetically using both Bayesian inference and parsimony. Uncorrected, the supermatrix yielded inconclusive results, demonstrating the presence of at least two phylogenetic optima. When the data were corrected according to new observations on Doleserpeton, Eocaecilia, and other fossil forms, the phylogeny supported the temnospondyl hypothesis of lissamphibian origins. This conclusion is also supported by a careful study of character changes in the individual lineages.

Comparative data on the differentiation and growth of bone ornamentation in gnathostomes (Chordata: Vertebrata)

“…The position of lissamphibians (the smallest clade that includes all extant amphibians) is controversial. For most of the 20th century, most authors have considered them to be nested within temnospondyls (e.g., Bolt, 1969;Ruta and Coates, 2007;Sigurdsen and Green, 2011), but several analyses involving one of us (M.L.) have recently supported a position in lepospondyls instead (e.g., Laurin, 1998;Vallin and Laurin, 2004;Marjanović and Laurin, 2013), a result also obtained by Pawley (2006) in one of her analyses.…”

Two new species of the genusBatropetes(Tetrapoda, Lepospondyli) from the Central European Rotliegend (basal Permian) in Germany

“…In more current studies, doubts have arisen regarding its monophyly. Cladistic analyses cannot confirm it as a monophyletic taxon (Ruta, 2003;Vallin and Laurin, 2004;Anderson, 2007;Sigurdsen and Green, 2011), but no other appropriate term exists for this unstable group, so 'Microsauria' is used in this study.…”

New specimen of <i>Cacops woehri</i> indicates differences in the ontogenetic trajectories among cacopine dissorophids

“…Dissorophoidea is a large clade that was very successful during the Paleozoic and continues to be so today, as most authors consider some or all three groups of modern amphibians to be part of Dissorophoidea (Anderson, 2008;Anderson et al, 2008b;Milner, 1988Milner, , 1993Schoch and Milner, 2004;Sigurdsen and Green, 2011), but see, for example, Marjanović and Laurin (2013) for a different view. Recent phylogenetic analyses have recovered two distinct subclades within fossil dissorophoids, one comprising the Olsoniformes (dissorophids and trematopids) and one comprising the Xerodromes (amphibamids and branchiosaurids) (Anderson et al, 2008b;Fröbisch and Schoch, 2009;Schoch, 2012;Schoch and Milner, 2014).…”