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A fossil named after curator Burke told the story of evolution – GeekWire



Carlos Mauricio Peredo
Carlos Mauricio Peredo, a researcher at the National Museum of Natural History, exhibited new 33 million-year-old fossils of whales classified as Maiabalaena nesbittae. (Smithsonian photo)

A whale that lived 33 million years ago when Oregon is part of the ocean floor was just named a curator at the Burke Museum of Natural History and Culture in Seattle.

And whale Elizabeth Nesbitt is not your ordinary cetacea: The fossil analysis, published in the November 29 issue of the journal Current Biology, shows that Maiabalaena nesbittae bridges the gap between teeth with whale species and species that have different mouths. eating mechanism known as baleen.

"For the first time, we can now write down the origins of filters, which is one of the main innovations in the history of whales," said study co-author Nicholas Pyenson, curator of the National Museum of Natural History fossil marine mammals and affiliate curator at the Burke Museum , said in a news release.

The M. nesbittae fossil was discovered in 1970 and has been widely studied since then. But the rock matrix and the material surrounding the fossils obscure many of its characteristics, which makes the formal classification frustrated. Then Carlos Mauricio Peredo, a researcher at the National Museum of Natural History, gave the fossil a thorough cleansing and examined it with sophisticated X-ray scanning technology.

Looking closely at the scan showed that M. nesbittae's jaw bone had no teeth. That in itself is not surprising: Whales, which may be measured as long as 15 feet in life, lived in an era when several species of whales made the evolutionary transition from using teeth to using baleen instead.

Baleen is a row of flexible and hair-like plates used by whale species such as humpback whales and blue whales to filter small prey from giant gulps of sea water. Feeding techniques allow baleen whales to consume tons of food every day without biting or chewing.

What makes M. nesbittae special is its thin and narrow upper jaw, which seems to make it unsuitable for supporting balin structures.

"Living balin whales have large and wide roofs in their mouths, and they also thicken to make attachment sites for baleens," said Peredo, who is the lead author of current Biology studies. "Maiabalaena doesn't. We can clearly tell you that this fossil species does not have teeth, and that is more likely than not having baleen, too. "

That would support the hypothesis that some species of toothed whales evolved to take advantage of feeding strategies that did not require teeth or balin.

Peredo and his colleagues said the muscle attachment to M. nesbittae's bones showed that it had strong cheeks and a retractable tongue. They suggested that whales could suck large amounts of water in their mouths, take small fish and squid in the process … without the necessary teeth. (Modern narwhal, which only has two vestigial teeth, uses the same strategy.)

In this scenario, loss of teeth sets the stage for the appearance of baleen filter structures — eating millions of years later. The main factor behind the differences in eating strategies is probably the dramatic cooling of sea water during the transition from Eocene to the Oligocene, about 34 million years ago.

The status of M. nesbittae which appears as a transitional species is reflected in the genus name that Peredo and his colleagues chose for their formal description of fossils.

"His name is Maiabalaena, which combines" Maia, "which means mother, and" balaena, "which means whale," Peredo said. "This is named after its position near the base of the balin whale family tree."

Peredo said the name of the species, nesbittae, the honor of Nesbitt "for his lifetime contribution to Pacific Northwest paleontology and his guidance and collegiality at the Burke Museum."

Elizabeth Nesbitt
Elizabeth Nesbitt is the curator of invertebrate and micropaleontology paleontology at the Burke Museum. (Photo of University of Washington)

Nesbitt studied fossils throughout western North America, with special emphasis on marine fossils. His research also focuses on modern Puget Sound microbiota, and how small creatures known as foraminifera function as key indicators of Puget Sound's health. (Spoiler warning: The indicator doesn't look good.)

In addition to his research, Nesbitt played the role of public outreach as curator of Burke's invertebrate paleontologist and micropaleontologist. The museum said he had put together various exhibits about the subject ranging from Pacific Northwest seismic history to imaginative representations of ancient fossils when they saw them in life.

Peredo is familiar with Nesbitt's work partly because his own research has used fossils extensively from the states of Washington and Oregon – including, of course, fossils that now use his name.

In addition to Peredo and Pyenson, the authors of the current Biology paper, entitled "Tooth Loss that Precedes Baleen's Origins in Whales," including Christopher Marshall and Mark Uhen.


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