Taxonomic Revision of the Short Nose Chimaeras (Genus Hydrolagus) from the Southern African Region

Short-nose chimaeras are an enigmatic and understudied group of deep-sea Chondrichthyan fishes. To resolve decades of confusion and misidentification in the southern African region, morphometric and genetic data were utilized to resolve taxonomic confusion for the genus Hydrolagus. Nearly 100 chimaeroid specimens were examined from numerous national and international museum ichthyology collections. A series of 96 measurements per specimen were recorded and analyzed with multivariate statistics to determine differences among species. Tissue was collected from various southern African species for analysis of the mitochondrial gene NADH2. The resulting genetic information was compared to morphologically similar species and those within the same geographical region. This study re-describes Hydrolagus africanus, officially describes a new species Hydrolagus erithacus sp. nov, identifies a species known as Hydrolagus cf. trolli as Hydrolagus affinis, and provides taxonomic clarification and detailed descriptions for all three species. The morphological and genetic differences between species of this genus are not pronounced, presenting challenges for identification and classification. Species clarification enables improved identification and fisheries statistics, informed management efforts, and the advancement of chimaera genetic and biological research