Evolutionary relationships of the lungless caecilianAtretochoana eiselti(Amphibia: Gymnophiona: Typhlonectidae)

Abstract

Appreciation of the diversity of caecilian amphibians has recently been enhanced by the discovery of a radically divergent aquatic caecilian of the Neotropical Typhlonectidae.Atretochoana eiseltiis the largest lungless tetrapod and the only lungless caecilian, and it possesses a suite of remarkable cranial modifications that set it apart from all other caecilians. Numerical phylogenetic analyses, using 141 morphological characters, were performed in order to resolve the evolutionary relationships ofAtretochoanaand representatives of all other typhlonectid genera. These analyses yield a single most parsimonious tree, (Chthonerpeton (Nectocaecilia (Typhlonectes natans, Typhlonectes compressicauda) (Potomotyphlus, Atretochoana)))), that is both well resolved and, as judged by Bremer support and by bootstrapping, is well supported. This tree is used as a basis for interpreting ecological shifts and associated morphological evolution within the Typhlonectidae. The available data suggest that the rate of morphological evolution in theAtretochoanalineage is significantly greater than that in other typhlonectid lineages.