Twenty years after: What larval characters are still telling us about the phylogeny of frogs (Amphibia: Anura) Authors Pedro Henrique dos Santos Dias, Alexander Haas, and Denis Jacob Machado (presenter). Abstracts The impact of phenotypic evidence in largely DNA-dominated matrixes has been widely documented in the literature. It has been demonstrated that phenotypic characters can improve clade resolution, affect the positioning of specific taxa, and increase the relative branch support of phylogenetic hypotheses. Moreover, fossils can only be placed in trees if morphological characters are included. Finally, the best explanation and the severe test for a given hypothesis should be based on the total evidence available. Even so, the usage of phenotypic characters is often disregarded in phylogenetic analyses. In this study, we evaluated the impact of larval morphology on the phylogeny of anurans (frogs and toads). The relationship between larval morphology and the systematics of anurans can be tracked down to the 19th century when the French zoologist Fernand Lataste proposed a sub-ordinal classification of frogs based on the position of the spiracle. Several significant contributions have been produced since then. In 2003, Alexander Haas published a seminal paper on Cladistics called “Phylogeny of frogs as inferred from primarily larval characters.” In that study, he was able to anticipate several phylogenetic trends that the following generation of large-scale molecular studies has since supported. Twenty years later, we revisited Haas’ work and compiled all the literature information published after 2003. We also analyzed several other tadpoles. Our goals are twofold: 1) to test the impact of larval morphology on largely DNA-dominated matrices; and 2) to summarize the phenotypic variation in larval morphology reported in the last 20 years in a phylogenetic framework. To test the impact of larval morphology in the phylogeny of frogs, we assembled a sizeable phenotypic dataset containing 282 taxa and 137 phenotypic characters individualized from external morphology, musculoskeletal system, and visceral components of tadpoles. Additionally, we included up to 15 molecular markers, summing up to 13,982 characters for 206 taxa. We performed two different phylogenetic analyses under the parsimony optimality criteria: 1) solely the molecular characters and 2) molecular + morphology (total evidence). Relative branch support was estimated based on REP. We discuss the impact of larval characters, propose synapomorphies in different levels of inclusiveness, and explore major evolutionary trends in tadpole evolution. About the event This talk was presented by Denis Jacob Machado at the XLI Meeting of the Willi Hennig Society in Mexico City, Mexico, on July 30, 2024. Acknowledgements Leibniz Institut Zur Analyse Des Biodiversitätswandels (LIB) Marie Curie Actions University of Charlotte at North Carolina's Department of Bioinformatics and Genomics and the Computational Intelligence Center to Predict Health and Environmental Risks (CIPHER) research center The Willi Hennig Society