Fossil Discovery of Pygmy Right Whales on Northern Hemisphere Rewrites Their History

A rare sighting of a living Caperea at sea  (photo: Robert Pitman)
Fossil Discovery of Pygmy Right Whales on Northern Hemisphere Rewrites Their History
post by
Jonas Van Boxel

Palaeontologists have found two fossils of ancient pygmy right whales in Sicily and in Japan. The study, by an international team with researchers from our Institute, changes everything we thought we knew about this mysterious animal.

The pygmy right whale (Caperea marginata) is the smallest baleen whale species, but its enormous, overlapping ribs give it the appearance of a tank. It is the only whale that can see colour. Today, this species only lives in the southern oceans, where it has been spotted near the coasts of Chile, Tierra del Fuego, Namibia, South Africa, Australia and New Zealand. So far, fossils of its ancestors had also only been found in the Southern Hemisphere, which made scientists assume that the whole evolutionary history of this animal had occurred there. The new finds from the north refute that assumption.

‘Imagine stumbling across a kangaroo in Scotland, or a polar bear in Antarctica!’ says Felix Marx, palaeontologist at our Institute. His team describes two Caperea-like fossils: a partial skull from Japan, and an ear bone from Sicily. In geological terms, these specimens are relatively young: between 500.000 and 900.000 years in the case of Japan, and about 1.8 million years in the case of Sicily.

Ice Age

The researchers say that, when Caperea first evolved, it only lived in the south, like today. Around 2.5 million years ago, that changed. The beginning of the ice age cooled the tropical seas surrounding the equator, allowing Caperea to migrate northwards and expand across much of the Atlantic and Pacific oceans. Other marine mammals, such as elephant seals and several dolphins, underwent similar range expansions.

When temperatures rose, the tropical gateway became a barrier again. Northern and southern populations became separated and evolved in different directions:some turned into new species, while others – including Caperea– became extinct in one hemisphere over time.

This scenario can happen again todaybecause of global warming. As the tropics warm, they become ever more difficult for marine mammals to pass. Eventually, this will cause populations of widely distributed species to separate completely – a process that may give rise to new species, but could just as well lead to extinction. 

The study was published in Current Biology

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