Tadpole morphology and ontogeny of Vitreorana franciscana Santana, Barros, Pontes & Feio, 2015 (Anura: Centrolenidae) with taxonomic implications for the V. parvula (Boulenger, 1895) species complex

In this study, we describe the external morphology of late embryonic stages and the tadpole of Vitreorana franciscana and assess its phylogenetic position within the genus. We accompanied the development of tadpoles from an egg clutch and collected a tadpole from the species type locality. Embryos are opaque, whitish, and took 4.5 days to develop from Gosner stage 20 to stage 25. The tadpole exhibits the fossorial morphology typical of Centrolenidae, with a depressed body and an elongated and robust muscular tail. In life, the tadpole shows conspicuously dark dorsal pigmentation, contrasting with the generally lighter coloration reported for congeners. Most external morphological traits fall within the range of variation observed in V. parvula tadpoles. Phylogenetic analyses recovered V. franciscana as the sister species to V. parvula in a well-supported clade. These results suggest that the overall tadpole morphology is conserved within this clade, whereas several larval characters, particularly those of the oral disc, differ from those observed in other Vitreorana species, such as V. eurygnatha. The absence of larval data for some species hampers the reconstruction of transformation series within Vitreorana, indicating that further efforts are still necessary for a comprehensive understanding of tadpole evolution in the genus.