The putative lissamphibian stem-group: phylogeny and evolution of the dissorophoid temnospondyls

Dissorophoid temnospondyls are widely considered to have given rise to some or all modern amphibians (Lissamphibia), but their ingroup relationships still bear major unresolved questions. An inclusive phylogenetic analysis of dissorophoids gives new insights into the large-scale topology of relationships. Based on a TNT 1.5 analysis (33 taxa, 108 characters), the enigmatic taxon Perryella is found to nest just outside Dissorophoidea (phylogenetic defintion) but shares a range of synapomorphies with this clade. The dissorophoids proper are found to encompass a first dichotomy between the largely paedomorphic Micromelerpetidae and all other taxa (Xerodromes). Within the latter, there is a basal dichotomy between the large, heavily ossified Olsoniformes (Dissorophidae + Trematopidae) and the small salamander-like Amphibamiformes (new taxon), which include four clades: (1) Micropholidae (Tersomius, Pasawioops, Micropholis), (2) Amphibamidae sensu stricto (Doleserpeton, Amphibamus), Branchiosauridae (Branchiosaurus, Apateon, Leptorophus, Schoenfelderpeton) and (4) Lissamphibia. The genera Platyrhinops and Eoscopus are here found to nest at the base of Amphibamiformes. Represented by their basalmost stem-taxa (Triadobatrachus, Karaurus, Eocaecilia), lissamphibians nest with Gerobatrachus rather than Amphibamidae as repeatedly found by former analyses.