Largest dolphin species

Despite its common name suggesting otherwise, the world's largest species of dolphin is the killer whale or orca Orcinus orca, which is a member of the marine dolphin family, Delphinidae (NB – this family also possesses a single species of exclusively freshwater dolphin). The only current member of the genus Orcinus, the killer whale normally ranges in total length from 6 to 8 m in the male, and from 5 to 7 m in the female. The largest specimen ever recorded, however, was a male that measured 9.8 m and weighed over 10 tonnes (male killers usually weigh in excess of 6 tonnes, but far less than this exceptional specimen). It occurs in all oceans – polar, temperate and tropical – worldwide. Despite its whale epithet and huge size, the killer whale is a true dolphin, and a detailed study of its cytochrome b gene sequences suggested that its closest relatives were the snubfin dolphins of the genus Orcaella.