Ancient Sirenians of the Channel Islands

Geologists Find Sea Cow Fossil on Santa Rosa

The last remaining species of sea cow on the West Coast of North America, the Steller’s sea cow, pictured in this illustration, was hunted to extinction in the 1760s. They were monogamous and social and mourned their dead.
Courtesy Photo

Around 20-25 million years ago, when the Channel Islands were situated closer to where San Diego is today, a gentle, giant species of “sea cow” glided among North America’s warm West Coast shallows, using their strong lips to slurp up seagrass between deep breaths at the surface. The modern cousins of these ancient sirenians ― a scientific name derived from the mermaid “sirens” of Greek mythology ― include three species of manatee and one direct relative, the dugong, which live off the east coast of Africa.

The fossilized remains of a sea cow, which scientists think may represent an entirely new species of sirenians, was discovered last July in a steep ravine on Santa Rosa Island by a pair of United States Geological Survey (USGS) scientists mapping fault lines. A team of paleontologists led by Dr. Jonathan Hoffman with the Santa Barbara Museum of Natural History is now in the process of stabilizing and protecting the six- to eight-foot-long fossil before it’s excavated and transported this spring to a marine mammal taxonomic expert at the Natural History Museum of Los Angeles County for further study.

Hoffman and his crew just returned from their second trip to the island, where they applied adhesive to the sea cow’s bones, slathered its body in plaster medical bandages, and then covered the whole specimen in burlap to protect it from the elements and erosion. “This is my first sea cow,” Hoffman said during a staticky phone interview from the site. “I cut my teeth on digs for hoofed animals in eastern Oregon. This is special.”

The sea cow’s skull shape will be studied to pinpoint its relationship to other sirenians, and its heavily worn teeth will help researchers learn about its diet and age. Hoffman is also collecting nearby marine microfauna fossils, such as snails and clam shells, that could yield valuable information about the cow’s prehistoric environment.

“One of the things that’s been really exciting for me is to be working with the National Park [Service],” Hoffman said. “In October the Park Service celebrated National Fossil Day, and it was a lot of fun talking to the public about the fossils we’ve been finding, like the pygmy mammoth. It’s a really great of example of the parks curating the future of these fossils, of protecting history.”


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