Cetotheriidae

About the pygmy right whales

For most of the twentieth century the pygmy right whale sat alone in its own family, Neobalaenidae, an oddity with no obvious relatives. Morphological work published in 2012 and 2013 placed it instead inside Cetotheriidae — a family otherwise known only from Miocene fossils and assumed extinct for some two million years. On that reading the species is a living relict, the last of a lineage that was once the dominant group of baleen whales.

The skeleton is unlike anything else alive. The ribs are extraordinarily broad and flattened, overlapping into an almost solid casing around the chest, and the skull combines a right whale’s arched jaw with a rorqual-like dorsal fin. Adults reach only about six and a half metres, making this the smallest of the baleen whales by a wide margin.

It is circumpolar in the Southern Hemisphere between roughly 30 and 55 degrees south, and it is barely ever seen. Most of what is known comes from strandings; there is no abundance estimate for the species anywhere in its range, and its Least Concern listing reflects an absence of known threats rather than any count of animals.