Descriptions of six new species in <scp> White Cloud Mountain minnow Tanichthys albonubes </scp> complex ( <scp>Cypriniformes: Tanichthyidae</scp> ) in southern China

Tanichthys albonubes is a critically endangered freshwater fish in South China and is classified as a second-class state-protected animal in China. It is also a colourful ornamental fish and has been introduced into many countries and regions around the world. Previous studies have revealed that there are seven cryptic species in the T. albonubes complex. Here, six new species of these cryptic species were diagnosed and described based on external morphology, colour patterns and osteological characteristics: Tanichthys shenzhenensis sp. nov., Tanichthys huidongensis sp. nov., Tanichthys luheensis sp. nov., Tanichthys dongxingensis sp. nov., Tanichthys guipingensis sp. nov. and Tanichthys hainanensis sp. nov. In addition, an identification key to the genus Tanichthys was provided. The key diagnosable characteristics of six new species in T. albonubes complex include the margin colour of dorsal and anal fins, the number of branched dorsal and anal fins, the relative position of the orbitosphenoid to the parasphenoid, the states of the neural complex, the states of the neural spine of the fourth vertebra and the anterior process of the innominatum. These six new species were also well supported by the phylogenetic tree and uncorrected p-distances based on Cyt b sequences. The distribution pattern of the genus Tanichthys is characterized by point-like, discontinuous distribution and geographically isolated on a large scale with narrow distribution ranges of each species. This study provides scientific data for the taxonomy, conservation status assessment and evolution of Tanichthys.