False killer whale  The false killer whale ("Pseudorca crassidens") is an oceanic dolphin that inhabits oceans worldwide but mainly frequents tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from the similar skull characteristics to the killer whale ("Orcinus orca"). The false killer whale reaches a maximum length of , though size can vary around the world. It is highly sociable, known to form pods of up to 500 members, and can also form pods with other dolphin species, such as bottlenose dolphins ("Tursiops truncatus"). Further, it can form close bonds with other species, as well as partake in sexual (including both heterosexual and homosexual) interactions with them. Conversely, the false killer whale has also been known to feed on other dolphins, though it typically eats squid and fish. It is a deep-diving dolphin, with a maximum recorded depth of ; its maximum speed is around . The false killer whale easily adapts to captivity and is kept in several aquariums around the world, though its aggression towards other dolphins makes it less desirable. It is threatened by fishing operations, as it can become entangled in fishing gear. It is drive hunted in some Japanese villages. The false killer whale has a tendency to mass strand given its highly social nature, with the largest stranding consisting of 805 beached at Mar del Plata, Argentina. Most of what is known of false killer whale comes from examining stranded individuals. The false killer whale was first described by the British paleontologist and biologist Richard Owen in his 1846 book, "A history of British fossil mammals and birds", based on a skull discovered in 1843. The skull was found in Stamford, Lincolnshire in England and dated to the Middle Pleistocene around 126,000 years ago. He found the skull comparable to the long-finned pilot whale ("Globicephala melas"), the beluga whale ("Delphinapterus leucas"), and Risso's dolphin ("Grampus griseus")–in fact, he gave it the nickname "thick toothed grampus" in light of this and assigned the animal to the genus "Phocaena" (a genus of porpoises) which Risso's dolphin was also assigned to in 1846. The species name "crassidens" means "thick toothed".