Larval morphology, vocalisations, and phylogenetic position of Crossodactylus dantei (Anura: Hylodidae): new insights into a little-known anuran species

Abstract

Aspects of the biology and natural history of the endemic anuran Crossodactylus dantei remain unknown even almost 30 years since its description. In this study, we describe its larval stage, along with the advertisement and territorial calls, and assess its phylogenetic positioning based on a fragment of the 16S rRNA mitochondrial gene. The larval stage of C. dantei follows the morphological pattern of Hylodidae, corroborating the relatively uniform larval morphology of the family. However, it is still possible to observe characters that distinguish C. dantei from other species in the genus, such as the elliptical body in dorsal view, nostrils located closer to the snout than to the eyes, an elongated pre-nasal arena, and the absence of taenia tecti medialis and taenia tecti transversalis in the chondrocranium. Its advertisement call is characterised by a sequence of about 23 pulsed notes, with ascending amplitude modulation, and has a mean duration of 2.5 seconds, with a dominant frequency of 3356 Hz. The territorial call has a mean duration of 23 seconds, a dominant frequency of 3160 Hz, and two distinct types of notes. Phylogenetic analysis indicated the existence of two main lineages in the genus. Crossodactylus dantei was recovered with high statistical support as a sister species to the clade composed of C. gaudichaudii and C. timbuhy. Furthermore, the group formed by these three species was recovered as the sister lineage of C. trachystomus. In summary, the information presented here represents a significant advance in the knowledge of this enigmatic and rare species of the northern Atlantic Forest, providing baseline data for future ecological and evolutionary studies of this unique frog. Keywords: tadpole, oral anatomy, chondrocranium, calls, phylogeny, Atlantic Forest