Clarification of Phylogenetic Relationships among Chinese Nemacheilids with Tube-Shaped Anterior Nostrils, with a Description of a New Genus and Two New Species

Nostril structures are important characteristics for generic diagnosis in Nemacheilidae and Cobitidae. Based on phylogenetic analysis, we found that 10 genera within Nemacheilidae (Eonemachilus, Guinemachilus, Lefua, Micronemacheilus, Oreonectes, Paranemachilus, Protonemacheilus, Traccatichthys, Troglonectes, and Yunnanilus) shared tube-shaped anterior nostrils and formed a monophyletic group. Morphologically, the location between the anterior and posterior nostrils was divided into three types: (i) separated, i.e., a distance greater than 1.5 times the diameter of the posterior nostril; (ii) adjacent, i.e., a distance shorter than the diameter of the posterior nostril; and (iii) closely set, i.e., posterior margin of the anterior nostril connected to the anterior margin of the posterior nostril. Thus, the 10 genera can be distinguished based on nostril features. Additionally, we describe one new genus, Guinemachilus gen. nov., and two new species, Guinemachilus pseudopulcherrimus sp. nov. and Paranemachilus chongzuo sp. nov.