Comparative buccopharyngeal morphology of tadpoles of Sphaenorhynchini (Anura: Hylidae: Hylinae)

The hylid tribe Sphaenorhynchini includes 15 small, greenish treefrog species within the genera Sphaenorhynchus and Gabohyla. Sphaenorhynchus is divided into three species groups: S. lacteus, S. planicola, and S. platycephalus, with S. carneus and S. prasinus remaining unassigned to any group; Gabohyla is monotypic. Larvae of most species have been described, except for S. botocudo, S. cammaeus, and S. mirim. Although larval morphology holds phylogenetic and diagnostic importance in Sphaenorhynchini, internal morphology remains largely unknown, with only the presence of a lingual papilla noted in S. dorisae and S. lacteus. To fill this gap, we describe the buccopharyngeal cavity of G. pauloalvini, S. prasinus, S. dorisae, S. lacteus, S. canga, and S. palustris. We provide a detailed description of this system for the tribe and discuss putative new larval synapomorphies. Tadpoles of Sphaenorhynchini show similarities in buccopharyngeal cavity morphology but vary in features such as prenarial arena shape, lateral ridge papillae, median ridge, and postnarial crest development. Gabohyla pauloalvini shows reduced lateral ridge papillae, which is an autapomorphy. Lateral roof papillae and a second pair of lateral ridge papillae are putative synapomorphies of the S. platycephalus group or one of its internal clades. The postnarial crest, present in all species, may be a synapomorphy of Sphaenorhynchini. These results enhance understanding of larval morphology and its systematic relevance within the tribe.