FIGURE 4.

Age of origin of Lissamphibia. (A) Various branches that may have given rise to the lissamphibian stem in the Paleozoic at points I through V. Under hypotheses of polyphyly, extant amphibians derive from both lepospondyls (at least for gymnophionans) and dissorophoid temnospondyls (anurans and, typically, urodeles). (B) Molecular ages of various lissamphibian clades proposed by Zhang et al. (2005). Bars represent 95% credibility intervals. (C) Colored bars: confidence intervals on the age of appearance of lissamphibians, given the stratigraphic distribution of fossiliferous localities that have yielded lissamphibians, and assuming an exponential diversification model and various assumed extinction levels of lissamphibians resulting from major biological crises (colored bars 1–4). A model that assumes no impact of major crises on lissamphibians yields a much longer confidence interval (bar 5), whereas one assuming no diversification yields a ridiculously short interval (bar 6). Each bar represents a 75% CI, and the black line in the bar represents the 50% CI. The background tree comes from Marjanović and Laurin (2007) and shows ranges of ages based on different assumptions about minimal branch lengths. Reproduced from Marjanović and Laurin (2008).