What is the smallest baleen whale species, according to modern scientific classification?

The pygmy right whale is the smallest baleen whale species according to modern scientific classification.

Pygmy right whales usually reach about 6.5 metres, making them much smaller than true right whales. They live mainly in temperate and subantarctic waters of the Southern Hemisphere and are rarely seen because they are unobtrusive and spend much of their time offshore.

The species has a strongly arched mouthline and a small, curved dorsal fin, features that help distinguish it from minke whales. Its baleen plates filter small prey such as krill and copepods from seawater.

The name can cause confusion because the animal is not simply a miniature version of a northern or southern right whale. It is the only living species in the family Cetotheriidae, a lineage once thought to have disappeared until the pygmy right whale was recognised as its surviving member.