Two new species of Eleutherodactylus from western and central Mexico (Eleutherodactylus jamesdixoni sp. nov., Eleutherodactylus humboldti sp. nov.)

Background: The subgenus Syrrhophus (genus Eleutherodactylus) contains >40 species of small, direct-developing frogs that occur at low to moderate elevations from Texas through Mexico and into Guatemala and Belize, with two species in western Cuba. Morphological conservatism and phenotypic convergence have made species delimitation challenging and resulted in a complicated taxonomic history. Since 2015, molecular systematic work has uncovered eleven new species from western Mexico and one from eastern Mexico, but current taxonomy still underestimates species level diversity and there is confusion surrounding the validity and boundary of several species. Methods: We used phylogenetic analysis of 16S ribosomal RNA (rRNA) sequences, multivariate statistical analysis of morphological data, and bioacoustic analysis of male advertisement calls to discover two additional unnamed species of Eleutherodactylus from Central and Western Mexico. We describe those species here. Results: Eleutherodactylus (Syrrhophus) humboldti sp. nov. is described from the Quaternary Valle de Bravo volcanic field of the Eje Neovolcanico in Central Mexico. This species is sister to E. maurus and is 3% divergent in 16S. Eleutherodactylus (Syrrhophus) jamesdixoni sp. nov. is described from the Sierra Madre Occidental of western Mexico. This species is sister to E. nitidus and is 3% divergent. We provide color photographs, advertisement call recordings, and molecular diagnoses of these new species and their sister species to aid future workers.