Pimelodus grunniens Humboldt, 1821 Rhamdia grunniens (Humboldt, 1821) Phractocephalus bicolor Spix & Agassiz, 1829 The redtail catfish , Phractocephalus hemioliopterus , is a pimelodid (long-whiskered) catfish named for its red or orange caudal fin . In Venezuela it is known as cajaro and in Brazil and even in a few parts