Assessment of the validity of Saurida microlepis (Aulopiformes, Synodontidae): An integrative morphological and genetic analysis

The validity of Saurida microlepis has long been debated, owing to close morphological similarity with congeners and the unavailability of the type specimen. We re-evaluated the species validity of S. microlepis through integrative analyses of morphological traits and mitochondrial cytochrome c oxidase subunit I sequences from 108 specimens collected along the coastal waters of China, including the type locality. Specimens were divided into three groups according to vertebral, lateral-line, and pre-dorsal-fin scales: forms matching S. eso , previously included as a synonym of S. elongata ; forms corresponding to S. microlepis ; and forms showing broad ranges across these traits. Morphological analyses revealed extensive overlap in both meristic and morphometric characters, demonstrating that they are insufficient for reliable discrimination. Genetic analyses revealed low intraspecific divergence and no distinct phylogenetic clustering. The results do not support recognition of S. microlepis as a valid species, and it is here confirmed as a junior synonym of S. eso . The different distribution patterns of S. eso and S. microlepis , combined with divergences in vertebral, lateral-line, and pre-dorsal-fin scales, suggest they may represent distinct populations of the same species. This study demonstrates the importance of combining morphological and molecular evidence to resolve taxonomic challenges in marine fishes.