The biogeography of otophysan fishes (Ostariophysi: Otophysi): a new appraisal

Abstract

Aim To present a new hypothetical history of the otophysan fishes.Location World-wide.Methods Utilization of recent information about otophysan phylogeny, palaeontology, biogeography and external relations.Results Anatomical, mitochondrial DNA and karological research has indicated that the Cypriniformes is the most primitive of the four orders that comprise the Otophysi. The Siluriformes is next in the phylogenetic progression followed by the Characiformes and the Gymnotiformes. A molecular clock estimate indicated that the divergence time between the cypriniforms and the remaining otophysans took place about 250 Ma. But, otophysans have apparently never occurred on Madagascar-India and that land mass did not separate from Africa until 158-160 Ma. As we know that some otophysans existed in Africa-South America prior to 115 Ma, they must have originated between 115 and 160 Ma.Main conclusions Comparison of phylogeny and biogeography appears to indicate that the Otophysi originated in South America, the location of the apomorphic Gymnotiformes. It seems that the gymnotiforms did not radiate in time to get across to Africa and the characiforms did not expand in time to catch the connection to Asia. Apparently, it was only the ancestors to the cypriniform and siluriform lines that expanded early enough to reach Asia in the late Jurassic. There remains a gap of about 80 Myr between the oldest known otophysan fossil and the approximate time of dispersal to Asia. Further progress awaits more phylogenetic or fossil discoveries.