Abstract

Gymnodiptychus Herzenstein, 1892, a genus of the subfamily Schizopygopsinae, currently comprises three valid species: Gymnodiptychus dybowskii, Gymnodiptychus pachycheilus, and Gymnodiptychus integrigymnatus. Previous molecular phylogenetic studies have suggested that the genus is not monophyletic, but the taxonomic status of Gymnodiptychus integrigymnatus has not been comprehensively reassessed. In this study, we conducted an integrative taxonomic investigation of Gymnodiptychus based on mitochondrial genome data, combined with morphological and osteological evidence. Phylogenetic analyses using the concatenated sequences of 13 mitochondrial protein-coding genes and two ribosomal RNA genes recovered Gymnodiptychus as non-monophyletic. Gymnodiptychus dybowskii and Gymnodiptychus pachycheilus formed a monophyletic clade sister to Diptychus, whereas Gymnodiptychus integrigymnatus formed an independent lineage sister to Schizopygopsis. Genetic distance analyses further revealed substantial divergence between Gymnodiptychus integrigymnatus and other members of Gymnodiptychus. Morphological and osteological comparisons demonstrated that Gymnodiptychus integrigymnatus differs markedly from the other two species, Gymnodiptychus dybowskii and Gymnodiptychus pachycheilus, in lacking pectoral girdle scales, possessing extremely reduced maxillary barbels, having a terminal mouth, and lacking the supraorbital bone. Based on this combined evidence, we establish the new genus Gaoligongia gen. nov. for Gymnodiptychus integrigymnatus Mo, 1989, which is herein reassigned as Gaoligongia integrigymnata (Mo, 1989), comb. nov. We also provide a revised diagnosis of Gymnodiptychus and a key to the genera of Schizopygopsinae.

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