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Giant extinct mammal identified from Unalaska fossils

  • Author: Mike Dunham
  • Updated: September 28, 2016
  • Published October 7, 2015

It had the face of a walrus, swam like a polar bear, was as big as a hippopotamus and sucked its food off the rocks and mud around the Aleutian Islands 23 million years ago. "Ounalashkastylus tomidai" was described by a team of paleontologists from Texas, Canada and Japan in an article published in the scientific journal Historical Biology on Oct. 1.

Louis L. Jacobs, a vertebrate paleontologist at Southern Methodist University in Dallas and co-author of the study, said in a press release the extinct marine mammal was a vegetarian with a long snout and tusks. It grazed on plants growing along the shoreline, rooting them out then sucking them in like a vacuum cleaner. It was a style of eating not found in any other animal.

The new species, a member of the order Desmostylia (des-mo-STILL-ee-uh), was identified from four specimens found on Unalaska over a period of years beginning in 1950, when fossils were discovered in a quarry. More emerged during excavations for the foundation of Eagle View Elementary School, said Alaska artist Ray Troll, an avid follower of paleontology and illustrator of extinct animals.

Anthony Fiorillo of the Perot Museum of Nature and Science in Dallas, another co-author of the study, told Alaska Dispatch News the find involved a good deal of serendipity. Fiorillo, who has made several important paleontological discoveries in Alaska, had planned to work in the Yukon-Charlie area in 2004, but wildfires and smoke made that impossible.

"I looked at the weather map, and the only place I could find that wasn't affected was Unalaska," he said. So he switched his destination. While there he gave a talk at the Museum of the Aleutians, where he learned about the fossils. They were being kept at the headquarters of the local Native corporation. "The Unalaska museum facilitated the loan of the fossils to the Perot Museum where we could study them. Louis Jacobs was with me, so it made sense for us to work on it together."

The scientists were hampered by the complex matrix of material in which the fossils were embedded and the fact they had not been present during the excavation. The time consuming work was "back-burnered" for a while as the Perot Museum was under construction, Fiorillo said. "We were finally able to get back to it and made the realization that we had something brand new about a year ago."

Little is known about the tribe of Desmostylians, the only known order of marine mammals to go completely extinct. Fossils are uncommon. "There's a lot of debate about who they're related to. Some say elephants, others say horses or manatees," Fiorillo said. "The bottom line is we have no idea."

"In my mind it looked a bit like a dugong, but with front limbs and hind limbs," he said. "We're pretty convinced it was a vegetarian. Structures in the mouth suggest that it had a very, very different feeding system, that when it was time to eat, it clamped down its jaws, opened its lips and just inhaled."

Though it had legs, it was primarily a marine animal, Fiorillo said. "Pretty much like seals, it could go on land, but you wouldn't find it roaming the landscape." In the water it would have used its powerful forearms, like a swimmer doing a breaststroke or a polar bear.

The fact that several individuals were found in one place indicates they lived "in some sort of cohort," said Fiorillo. And, as a group of lions is a pride and a group of cows is a herd, Jacobs has proposed calling cohorts of Desmostylians a "troll" in honor of artist Troll, who has made paintings of the animal among his many other paleontological renderings.

One of the Unalaska fossils was of a young animal."That suggests to me that Unalaska was a good place for Desmostylia to raise a family," said Fiorillo. "It was probably an area for birthing or rearing."

Fossils of other Desmostylian species have been recovered along the Pacific Coast from Baja California to Japan. The Alaska fossils, which are different from the others, are the farthest north to have been found.

The name of the new species combines Unalaska with a description of the animal's unique, column-like teeth. "Tomidai" honors Yukimitsu Tomida, a Japanese paleontologist who has done research into Desmostylians.

The fact that Ounalashkastylus came to light at all still makes Fiorillo chuckle. "Who would have imagined that the boreal fire cycle of Alaska would lead to the discovery of a new marine mammal in Unalaska?" he said.

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