Prehistoric Toothless Whale Among Oldest of Its Kind

Fossils unearthed in New Zealand belonged to an ancestor of minkes and humpbacks that lived about 27.5 million years ago.Friday, 20 April 2018

A fossil found on the South Island of New Zealand is now one of the earliest members of the filter-feeding family of behemoths known as baleen whales. Modern baleen whales include many of the world’s largest cetaceans, such as blue, fin, humpback, right, bowhead, and minke whales.

The new species has been named Toipahautea waitaki, which roughly translates to the Māori for "baleen origin whale of the Waitaki region." It dates back 27.5 million years, say the authors of a study describing it in the journal Royal Society Open Science. At this time in the mid-Oligocene epoch, the region was an island archipelago lapped by the shallow waters of highly productive seas.

Why is this discovery important?

The very ancient ancestors of modern whales and dolphins, or cetaceans, were land-living carnivores that entered the seas around 50 million years ago, slowly losing their legs through evolution and adapting to an ocean-going way of life. 

The first whales were all toothed, like modern sperm whales, says study author Ewan Fordyce at the University of Otago in New Zealand. But some later lost their teeth, developing plates of bristle-like baleen in their mouths that’s used to filter small prey such as krill from the water.

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Until recently, scientists have known very little about precisely when the first baleen whales evolved. The oldest known relative of baleen whales is the 36-million-year-old Mystacodon selenensis, which was discovered in Peru and described in 2017—but that species still had teeth. By contrast, Toipahautea had a long, toothless jaw and is thought to have fed using plates of baleen. 

“As sure as the sun rises in the east, we are going to find older baleen whale specimens,” says Fordyce. “But right now, it anchors the modern baleen whale lineage to at least 27.5 million years.”

How did paleontologists find it?

Three decades ago, Fordyce was awarded a grant from the National Geographic Society to search for fossil whales in New Zealand, which has since resulted in a series of discoveries of prehistoric whales and dolphins. 

The fossil of Toipahautea was found in January 1988 in the Hakataramea Valley in South Canterbury, but was only analysed in detail recently, when Fordyce’s co-author and former student Cheng-Hsiu Tsai—now at National Taiwan University—studied it for his Ph.D.

At 19 feet in length, or about half the size of a modern minke whale, Toipahautea was much smaller than most baleen whales today. “People look at the fossil record and think the early history of many animals is filled with giants, but not for whales. It's only in recent geological times that whales have achieved really large sizes,” Fordyce says.

What else does the find tell us?

Most of today’s baleen whales are feeding specialists. For instance, the various right whales use skim-feeding, swimming with their mouths open at the surface to strain out prey. Others called rorquals, such as humpbacks and blue whales, use gulp-feeding, taking in vast mouthfuls of water and krill and then squeezing the water out.

But the study authors suggest that early baleen whales like Toipahautea were generalists that used a variety of feeding styles.

“This is the oldest representative of the common ancestor of those two living groups, so that puts the split between those two groups at least back at 27.5 million years,” Fordyce says. Other early baleen whale relatives may have sucked up food, or used their teeth to filter it from the water.

“This is a fantastic fossil find from a fascinating period of Earth’s history, when early whales were extremely diverse,” comments David Hocking, an expert on the evolution of aquatic mammals at Monash University in Melbourne, Australia.

And with further fossils discoveries and more study, that diversity might continue to tell paleontologists how modern whales came to behave the way they do.

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