Paragenidens, a new genus of ariid catfishes is proposed to accommodate Arius grandoculis, a species previously assigned to the genus Potamarius. Paragenidens grandoculis is an endemic ariid catfish categorized as Critically Endangered and probably Extinct from coastal lacustrine systems from Espírito Santo and Rio de Janeiro states, southeastern Brazil. After more than 50 years without records of the species, new recent fieldwork revealed that the species is extinct at lagoa Juparanã, but still can be found at lagoa Nova in Linhares municipality, Espírito Santo state. Here, Paragenidens is described based on morphological and molecular evidence. In addition to its generic reassignment, the species is redescribed, and comments on its phylogenetic relationships, biogeography and conservation are presented.
Keywords: Reptilia, Threatened species, endemic, phylogenetic relationships, conservation, Atlantic rainforest, Paragenidens gen. n..