How Whales' Ancestors Left Land Behind

Wynne Parry, LiveScience Contributor

Date: 20 March 2013 Time: 06:26 PM ET

NEW YORK — By moving into the water full-time, the ancestors of whales paved the way for their descendants to become behemoths, largely free from gravity's constraints. Today, the blue whale is the largest animal ever to live.

But even before the move, this lineage was setting size records. One ancient cousin to modern whales and hippos, called Andrewsarchus mongoliensis, ranks as the largest mammal known to have stalked the land as a predator. A skull from this creature — the only fossil found so far from this beast — greets visitors on their way into a new exhibit on whales here at the American Museum of Natural History.

"It's odd to have a big predator in this hoofed plant-eating mammal group," said John Flynn, co-curator of the exhibit, referring to the group to which whales and the now-extinctAndrewsarchus belonged. "But if you think about it, some of the other relatives like pigs and peccaries are pretty ferocious and will eat just about anything."

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