When All Whales Were Killers

An ancient fossil shows what came before baleen: big, nasty teeth.

By Kathryn Garfield
Dec 8, 2006 6:00 AMNov 12, 2019 4:31 AM
A 25-million-year-old foot-and-a-half-long skull from an ancient, predatory baleen whale.<a target="_blank" href="http://www.museum.vic.gov.au/index.asp"></a> | Museum Victoria


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Baleen whales are gentle giants, roaming the oceans like enormous cows. Despite their massive size, humpbacks, blue whales, and their brethren do harm to no other sea life except the plankton and krill they suck in through their screenlike baleen filters. But an astounding fossil discovery is offering scientists a glimpse into the distant, ferocious past of today's mild-mannered mysticetes.

Staumn Hunder, an Australian surfer, discovered the fossil on a beach in the late 1990s and had the presence of mind to turn it over to a Melbourne museum. When Monash University whale researcher Erich Fitzgerald first viewed the rock-encased fossil in 2001, he knew he'd come upon something utterly novel. It took more than two years to strip the stone from the whale skull, and when he did, "there before me was what looked like an entirely new branch on the evolutionary tree of whales."

All living whales belong to one of two branches of the whale tree—toothed or baleen. Toothed whales all navigate by echolocation and share distinct genetic markers that separate them from the baleen relatives they diverged from some 35 million years ago. Despite its impressive teeth, the ancient animal (named Janjucetus hunderi, partly in honor of its discoverer) has distinctive anatomical traits that place it firmly within the baleen branch.

As such, it provides the first real glimpse into what baleen whales were like before they evolved their feeding filters.Measuring about 9 to 11 feet long, the specimen was the size of a bottlenose dolphin, with huge eyes that took up a quarter of its head.Instead of echolocating, it most likely depended on keen underwater vision and sharp hearing to track fish and small sharks, which it would then tear apart and shred with its 1.4-inch-long serrated teeth.

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