Taxonomy, morphology and systematics of the genus Psilorhynchus (Ostariophysi: Cypriniformes: Psilorhynchidae)

Members of the genus Psilorhynchus are small benthic fishes, commonly referred to as torrent minnows, which inhabit the fast to swift flowing water bodies of the Indo-Burma region and the Western Ghats region of Peninsular India. Despite being described scientifically in the mid 18th century, the morphology of Psilorhynchus remains poorly known, and its phylogenetic placement within the order Cypriniformes is a matter of considerable debate. I conduct a detailed phylogenetic investigation of Psilorhynchus utilizing both morphological and molecular data sets. Parsimony analysis of the morphological data set (consisting of 127 osteological characters) provides strong support that Psilorhynchus is monophyletic and further suggests that Psilorhynchus is the sister group of the Cyprinidae. Parsimony, Maximum Likelihood and Bayesian analysis of a molecular data set of 3237 aligned positions (including 642 base pairs of CO1, 1140 base pairs of cytb and 1455 base pairs of RAG1) also provides strong support that Psilorhynchus is monophyletic and more closely related to members of the Cyprinidae than to members of other cypriniform families. Both morphological and molecular phylogenetic investigations recovered similar phylogenetic patterns between the species of Psilorhynchus included for investigation, supporting the division of the genus in to a number of species groups (including the P. balitora, the P. gracilis and P. homaloptera species groups). A detailed account of the osteology of P. sucatio is also provided together with a taxonomic diagnosis of the genus and redescriptions of four species (P. balitora, P. breviminor, P. nepalensis and P. rahmani).