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When you think about it, whales seem a bit strange. They live in the ocean, but breathe air. That suggests that millions of years ago, their ancestors walked on land. But the change didn’t happen overnight.

So what did whales look like when they were making the move from land to sea? Earlier this month, an international team of scientists described a fossil skeleton that helps to paint the picture.

The first whale

Meet Peregocetus pacificus. It’s about four metres long and lived millions of years ago, along the coast of what is now Peru. This curious creature was poised between the land and sea.

Its long toes were likely webbed to swim better, but they ended in hoofs for walking on land. Its legs were strong enough to walk around, but its tail was powerful, ready to swim. And its teeth were great for catching large bony fish.

Digging into the science

Everything we know about Peregocetus pacificus comes from just one fossilised skeleton, recently uncovered in Peru.

The rocks containing this fossil skeleton also included microfossils of small ocean creatures. By comparing these microfossils with ones found in other rocks, scientists can tell the fossil of Peregocetus pacificus formed 42.6 million years ago.

A lot of this ancient whale was preserved, including a front leg, a back leg, the lower jaw, pelvis and parts of the tail. Of the missing parts, the last bone in the tail would be particularly helpful. If we had that bone, we would be able to tell if Peregocetus pacificus had a tail fin like modern whales do!

More information

For modern whales, the ocean is an increasingly noisy place

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