Description and relationships of Otothyropsis marapoama, a new genus and species of hypoptopomatine catfish (Siluriformes: Loricariidae) from rio Tietê basin, southeastern Brazil

otothyropsis marapoama, a new genus and species, is described based on specimens recently collected in a headwater stream of the middle stretch of the rio tietê, a river from the upper rio paraná basin in southeastern brazil. the new taxon belongs to a clade also encompassing the genera schizolecis, otothyris and pseudotothyris. otothyropsis marapoama is hypothesized to be the sister-group of pseudotothyris and otothyris based mainly on the presence of several derived characters of the swimbladder capsule and associated bones. several paedomorphic characters shared by pseudotothyris and otothyris and their significance for the phylogenetic position of the new genus are discussed.