Which whale species has the smallest body size among all baleen whales?

The pygmy right whale is the smallest species among all baleen whales. Caperea marginata usually measures about 6 to 6.5 meters long, far smaller than the large rorquals and true right whales that dominate most people’s image of baleen whales.

It was first described by British zoologist John Edward Gray in 1846. For many years, its unusual anatomy made its evolutionary position puzzling. Modern anatomical and genetic research suggests that it is closely related to the cetotheres, a group of baleen whales once thought to be entirely extinct, giving the pygmy right whale unusual scientific importance.

Despite its name, it is not simply a miniature version of the better-known northern or southern right whales. It has a more slender body, a smaller and less obvious blow, a falcate dorsal fin, and distinctive narrow baleen plates. It feeds mainly on tiny crustaceans such as copepods and euphausiids.

The species lives in temperate waters of the Southern Hemisphere and is rarely seen at sea, so many details of its population, breeding, and behavior remain poorly known.