Diagnosis of Asian Raiamas (Teleostei: Cyprinidae: Chedrina) with comments on chedrin relationships and previously proposed diagnostic characters for Opsaridium and Raiamas

As currently recognized, Raiamas is the sole chedrin genus with a transoceanic distribution. While a previous morphological study suggested that Asian Raiamas are morphologically differentiated from their African congeners, a single transoceanic genus was retained. Among the characters previously proposed, only the plesiomorphic presence of maxillary barbels in Asian Raiamas serves to distinguish them from their African congeners. Here we provide five novel apomorphies that do diagnose Asian Raiamas as phylogenetically distinct from the African species. Molecular data corroborate the non-monophyly of Raiamas, indicating that the Asian species, Raiamas bola and Raiamas guttatus, form a clade that is sister to either the entire African chedrin assemblage or to the genus Opsarius. African Raiamas are not monophyletic and are instead arrayed in three groups. Review of previously proposed synapomorphies for Opsaridium and Raiamas suggests that none can be considered diagnostic for these two genera, and our study underscores the need for a comprehensive review of the generic composition and intrarelationships among the poorly studied African chedrins.