Cetotheriidae consists of only one living member: the pygmy right whale ("Caperea marginata"). The first descriptions date back to the 1840s of bones and baleen plates resembling a smaller version of the right whale, and was named "Balaena marginata". In 1864, it was moved into the genus "Caperea" after a skull of another specimen was discovered. Six years later, the pygmy right whale was classified under the family Neobalaenidae. Despite its name, the pygmy right whale is more genetically similar to rorquals and gray whales than to right whales. A study published in 2012, based on bone structure, moved the pygmy right whale from the family Neobalaenidae to the family Cetotheriidae, making it a living fossil; Neobalaenidae was demoted to subfamily level as Neobalaeninae.