Orcinus orca
CLASS: Mammalia
ORDER: Cetacea
SUBORDER: Odontoceti
FAMILY: Delphinidae
GENUS: Orcinus
SPECIES: orca
The Order Cetacea includes two sub-orders; Mysticeti (baleen whales) and Odontoceti (toothed whales)... meaning Orcas are in the same Class, Order but differing Famiy (there are, currently 5 recognized families within Cetacea) .
"...The terms whale, dolphin, and porpoise need explanation. As here used, the term whale is all-inclusive and may be applied to any cetacean. The term dolphin applies to those small whales that have a distinct snout or beak and numerous conical teeth that are roughly circular in cross-section. The term porpoise applies to those small, blunt-nosed whales that have flat, spade-shaped teeth." (Source: Order Cetacea...)