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The Then & Theory team

Whales had legs

A four-legged animal stands on the shore above a whale. The earliest whales walked. Pakicetus, known from fossils about 48.5 million years old in Pakistan, was about the size of a wolf, had working legs, ears better suited to air than water, and teeth that suggest a diet of fish. Its descendants moved into the sea for good. DNA shows that the closest living relatives of whales are hippos, and fossils such as Indohyus, an extinct hoofed animal that waded in water, point to where the whale line began.

Note. Hippos as the closest living relatives is settled by DNA. Which extinct group sits closest to whales is still debated.

Sources

1. Britannica, “Pakicetus”
2. Britannica, “What’s the closest living relative to whales?”
3. Thewissen et al., Nature (2007), Indohyus