The redtail catfish, Phractocephalus hemioliopterus, is a pimelodid (long-whiskered) catfish. In Venezuela, it is known as cajaro, and in Brazil, it is known as pirarara, stemming from the Tupi language words pirá and arara. It is the only extant species of the genus Phractocephalus. This fish is common in the aquarium trade, although its massive adult size makes it unsuitable for all but the largest aquariums. They feed on fish, crustaceans and fallen fruits. They are not evaluated by IUCN. Fossil species Although the redtail catfish is the only living representative of this genus, there are other members that date back to the upper Miocene, and are only known from fossil remains. P. nassi was described in 2003, from the Urumaco Formation at Urumaco, Venezuela. Another fossil species, P. acreornatus, is known from the Solimões Formation, Acre, Brazil. This genus has a minimum age of about 13.5 million years. Description Phractocephalus hemioliopterus can reach about in length, and about in weight. However, this is exceptionally rare, and most do not approach this size. They average in length. These colorful large catfishes have a brownish back, with yellow sides, and characteristic orange-red dorsal fin and caudal fin (hence the common name). Sometimes the dorsal, pelvic and anal fins are also red. They have a broad head with long whiskers, dark black body and white underneath that extends from the mouth to the caudal fin. It has a pair of barbels on the upper jaw, and two pairs on the lower jaw. Their whiskers are sensitive and have chemical reception cells which are used as the sense of smell. They breed using external fertilization after laying their eggs. They communicate by making a clicking sound to warn off potential dangers. Distribution and habitat The redtail catfish is native to the Amazon, Orinoco, and Essequibo river basins of South America, in Ecuador, Venezuela, Guyana, Colombia, Peru, Suriname, Bolivia, and Brazil. It is found only in fresh water, and inhabits larger rivers, streams, and lakes. They eat during the evening and night and stay motionless during the day. They are bottom-dwellers and move about quite slowly. Red-tailed catfish are territorial fish. Redtail catfish is also an invasive species in Malaysia, they are now found mostly in the Perak River and Pahang River. Relationship to humans Due to the potential large size of this species, redtail catfish are considered a game fish by anglers. The