New phenotypic synapomorphies delimit three molecular-based clades of New World direct-developing frogs (Amphibia: Anura: Brachycephaloidea)

Brachycephaloidea (composed of 1183 species) is the most diverse superfamily of amphibians. In recent years, molecular techniques utilizing genetic markers have significantly improved our understanding of the phylogeny of this superfamily. However, with the expansion of molecular techniques, phenotypic characters have received increasingly less attention. In an effort to highlight the contributions that phenotypic characters can make to understanding the phylogeny of Brachycephaloidea, we studied novel characters from pelvic and thigh musculature and digital discs on fingers. On this basis, we provide new phenotypic synapomorphies to recognize three clades previously recognized solely on the basis of DNA. The first two synapomorphies, related to the origins of the m. iliacus externus and m. tensor fasciae latae, diagnose Ceuthomantis and Phrynopus, respectively. The third synapomorphy, related to the relative size of the disc on finger I, diagnoses the Pristimantis conspicillatus species group, which is the largest species group within the species-rich genus Pristimantis. We conclude that phenotypic data are a valuable source of evidence in testing phylogenetic hypotheses of Brachycephaloidea and emphasize the need to reassess all phenotypic characters previously used in brachycephaloid taxonomy to delimit them objectively as transformation series and include them in total evidence analyses.

Automated summary

By studying the phenotypic characters of Brachycephaloidea, we have provided new synapomorphies to recognize three clades previously recognized solely on the basis of DNA. We conclude that phenotypic data are a valuable source of evidence in testing phylogenetic hypotheses of Brachycephaloidea.