Revision of Pimelodina and Description of a New Genus and Species from the Peruvian Amazon (Pisces: Pimelodidae)

The pimelodid catfish genus Pimelodina Steindachner is redefined on the basis of its swim bladder which is greatly reduced and almost fully encapsulated in the Weberian complex, its broad premaxilla with teeth confined to a row along the posterior margin and its extraordinary, gizzard-like stomach. Pimelodina nasus Eigenmann and Eigenmann was found to be a junior synonym of P. flavipinnis Steindachner, making the genus monotypic. P. flavipinnis inhabits larger rivers and lowland lagoons of the Amazon and Orinoco river basins in South America. Aguarunichthys torosus, a new genus and species from the Peruvian Amazon, is described based on its exceptional swim bladder, which has fingerlike projections along the posterolateral margin and a tubular extension projecting anteriorly to the level of the basioccipital and configuration of its subterminal mouth and dentition. Within the Pimelodidae, Pimelodina, Aguarunichthys, Calophysus, Pinirampus (including Perugia) and Luciopimelodus apparently constitute a monophyletic group which is defined on the basis of shared specializations of the Weberian complex and swim bladder, including: 1) the partial or complete encapsulation of a lateral extension of the swim bladder within transverse processes of the fourth vertebra; and 2) the non-encapsulated portion of the swim bladder being flattened and variously reduced or foreshortened with tubular extensions projecting anteriorly to the ventral surface of the cranium