Hector's beaked whale (Mesoplodon hectori), is a small mesoplodont living in the Southern Hemisphere.

[3][4][5][6][7][8][9][10][11][12][excessive citations] The English taxonomist John Edward Gray first named the species Berardius hectori in 1871, based on a specimen (a 2.82 metres (9 ft 3 in) male) collected in Tītahi Bay, New Zealand in January, 1866.

[13] The following year, 1872, English anatomist William Henry Flower placed it in the genus Mesoplodon, while in 1873, Scottish scientist James Hector assigned the same specimen to the species M. knoxi.

Beaked whale specialist Joseph Curtis Moore (1968) and J. G. B. Ross (1970) contested this designation, arguing that M. hectori was a valid species.

[15] However, the translation of this approach to rare species with elusive life histories, such as the Hector's beaked whales, can be problematic for many reasons.

Also, the usefulness of whole or partial "voucher" specimens in private collections to assign taxonomic difference based on morphology is equally susceptible to inaccuracy, and additionally can lead to unethical acquisition methods, such as illegal hunting of a rare species.

[3] This discovery was puzzling, because although the suspected range of Ziphius cavirostris was met by the stranding location, M. Hectori was thought to be restricted solely to the Southern Hemisphere.

[18] More recent phylogenetic analyses of nuclear actin sequences substantiated the validity of this classification, as a distinct 34 base-pair deletion was found in the allele, screened across all species, of the two M. perrini samples in particular.

[17] Reaching a maximum length around 4.2 m (1.9 m when born), and with an estimated weight around 1 tonne (1.032 tons), Hector's is one of the smallest of the beaked whales.

Additionally, oval white scars on the ventral portion of this male specimen were likely caused from cookie-cutter sharks of the Isistius species.

The fangs are possibly vestigial, or atavisms of some other kind, though a definitive answer is difficult because of the dearth of knowledge about the species.

[21] Hector's beaked whale has a circumpolar distribution in cool temperate Southern Hemisphere waters between about 35 and 55°S.