Researchers discover skull, ribs of extinct sea cow in Channel Islands National Park
Photo Credit: Juan Carlo, VC Star
Researchers on the Channel Islands recently discovered an extinct sea cow buried deep in a steep ravine on Santa Rosa Island.
Estimated to be 20 to 25 million years old, a skull and partially-intact skeleton were found in July.
The find marks a first for the five-island national park off Ventura and is possibly one of the oldest sea cow fossils uncovered on the West Coast.
“This is a really exciting find for that reason alone,” said paleontologist Jonathan Hoffman, crouched down in a dusty pocket of the ravine last week.
But the discovery also might be another first — a new species of sea cow, which are also called sirenians.
The skull will help experts tell that story, Hoffman said. But first, they need to excavate and preserve the bones.
Hoffman and his team navigated loose dirt and shifting rocks to uncover the skull and other bones.
Any teeth would help fill in the puzzle, Hoffman said. But right now, no one knows if any teeth will be found buried under the exposed bone.
A distant ancestor of today’s living manatees and dugongs, the torpedo-shaped animals typically lived in shallow water, ate sea grasses and grew to be about 10 feet long.
This one lived not only millions of years ago but also in a vastly different place.
When the sea cow wound up buried on the ocean floor, it would have been farther south, closer to where San Diego is today.
Over millions of years, plates shifted and rotated. The sea cow remains caught a ride on the tectonic plate with bits of rock that would later become the Channel Islands.
Probably in just the last few years, the bones were exposed as fierce wind and rain eroded the cliff.
And, it’s not just one sea cow they have found in the ravine.
“We don’t know the exact number. But it’s definitely more than one,” said Hoffman, the Dibblee collection manager of earth science at the Santa Barbara Museum of Natural History.
Last week, Hoffman and a volunteer crew of three used rock hammers and other tools to dig a perimeter around the bones. Then, using thinner metal picks, they slowly chipped away at the stone.
For now, the sea cows will stay put, protected by layers of medical bandages and plaster casts for the winter.
Hoffman hopes to be back in the spring, a plan ready and permits in hand to excavate and bring the rare fossils to the mainland to be prepared and studied.
In July 2012, Scott Minor was climbing down a cliff on Santa Rosa Island when something caught his eye.
The structural geologist with U.S. Geological Survey was checking out faults that crisscross the island and run through the ravine.
“I looked up and I thought I saw something kind of unusual sticking out,” he said. “I got a little closer and realized: That’s a ribcage.”
Minor photographed the bone, took some notes and recorded the GPS coordinates to pass on to experts.
It would be five years before a team of paleontologists came back to check out what, by then, some were sure was a sea cow.
Minor also returned. He scouted out the location with Kevin Schmidt, also with the USGS, and a park ranger just before the team got there.
That’s when they found the skull and nearby skeleton in a different spot in the ravine. The other bone was still in the cliff face but had significantly eroded in the wind-swept area.
As the paleontologists work on the bones, Minor has his own challenge. He will figure out the jigsaw puzzle of rock.
“The problem is you have these faults that cut everything up and kind of slice and dice the blocks of rock,” Minor said.
Unraveling it is kind of his specialty, he said. In this case, understanding how the faults moved could lead to more discoveries.
Meanwhile, researchers hope to use shells of clams and oysters found near the bones, as well as microscopic critters, to narrow the age of the bones.
“It’s really cool that this could potentially be a missing link for the paleontologists trying to understand the evolution of this family of marine mammals,” Minor said.
Researchers started the summer with bones found in two sites in the same ravine.
After days of working on the skull, Hoffman and his team found others, including one slab of loose rock in which several ribs were visible.
A team slowly, methodically carried the heavy stone up the steep hill on a litter usually reserved for injured hikers. It was loaded onto a boat last week and officially became the first sea cow bones taken off the fossil-rich Channel Islands.
The Santa Rosa find will help fill in the story of these ancient inhabitants of the California coast, said Jorge Velez-Juarbe, a sea cow expert at the Natural History Museum of Los Angeles County, which is expected to study the skull and bones.
"It may help us appreciate a little more these sort of ... lonely remnants of these large, enigmatic groups that used to be so diverse and now there are just a few," he said.
At one time, experts say there were more than a dozen different species of sirenians living around the world. The cause of their decline is unclear but may be linked to cooling temperatures and availability of seagrass.
Their modern relatives include manatees and the one remaining dugong found in the warm waters of the Pacific Ocean and off the east coast of Africa.
While this was a first for the islands, Hoffman said it's not unlikely that sea cow fossils would be found there.
It was probably a case of being in the right place at the right time to make the discovery, he said.
In the past, the coast along Santa Rosa and other parts of the Channel Islands National Park seem to have gotten the most attention. That’s where mammoth and archeological finds mostly have been uncovered.
The typically hard-to-access interior areas went less explored.
“I love the fact that we’re really working on some new stuff on the islands,” Hoffman said.
“This is a whole new area of the island and time period that hasn’t been explored yet,” he said. “So, to get started on that has been pretty great.”
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