There are no known fossils. Caperea is the smallest baleen whale.
Females apparently are larger than males.
A female 621 cm long weighed 3,200 kg, and a male 547 cm long weighed 2,850 kg. The coloration is black or dark gray above and paler below. The tongue and interior part of the mouth are pure white. There are 213-30 baleen plates on each side of the mouth. The plates are up to 70 cm long and are ivory white in color but have a dark outer margin.