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Digging Into a Fossil Find : Archeology: Scientists excavating remains of pygmy mammoth uncover two-foot tusk that is virtually intact.

August 12, 1994|PHYLLIS W. JORDAN | SPECIAL TO THE TIMES

SANTA ROSA ISLAND — After hours of excavating a rare pygmy mammoth fossil, archeologist Don Morris scrambled up a steep, sandy cliff and broke the news to a colleague.

"We've got a tusk down there," Morris said breathlessly. "It's really nifty. It's all in the sand, and it's in terrific shape."

Sure enough, the prehistoric skeleton discovered earlier this summer on Santa Rosa Island came complete with a 25-inch-long tusk, gleaming like polished wood in the bright, noonday sun.

The fossil is believed to be the most complete skeleton ever found of the mammoth that often grew no larger than a Saint Bernard.

This particular creature stood about 3 1/2 feet high at the shoulder, weighed up to 500 pounds and lived as long as 75,000 years ago, scientists estimated after their first day of excavation.

A team of scientists from across the nation began digging at the site Tuesday and by Wednesday they had already discovered key portions of the ancestral elephant's frame. By Thursday afternoon, the scientists had uncovered the entire skeleton and found all four legs of the mammoth intact, "even the little bones of the feet," park spokeswoman Carol Spears said.

Carefully, two scientists used dental picks to scrape sand from the mammoth's pelvis bone, the joint that could hold the answer to the animal's gender.

A biologist cleared sediment from the mammoth's eye sockets with a trowel and brushed sand off the bridge of its trunk.

As the scientists worked earlier this week, the jagged edge of the spine, bleached white from exposure, stuck out sharply from the eroding sand dune.

It was the spine that first drew a San Diego geologist to the fossil in June. Without that chance discovery, the rare skeleton could have been lost to exposure or to the sea, which is slowly eating away the aqua blue cove barely 100 feet from the dune.

"It's the luck of science," said Morris, archeologist for the Channel Islands Park Service.

The fossil's location, mostly in loose sand, is also a stroke of luck.

"This sand is like going through butter with a hot knife," said Larry Agenbroad, a paleontologist who studies mammoths at Northern Arizona University and the Mammoth Site in South Dakota. "I'm used to sand, but much more cemented sand."

The downside is that the steep slope makes it impossible to bring heavy equipment to the site. The digging is all done by hand.

Every step on the eroding dune sends showers of sand down the hill. A bright orange safety fence is all that separates the scientists and their equipment from a sea cliff and the surf below.

Agenbroad speculated that the mammoth may have died in a landslide that covered it with sand. Scientists believe the body was quickly buried in sand, initially sparing it from erosion and deterioration.

About 2,000 years ago, they estimate, a gully or arroyo developed, and water began running down the dune onto the remains.

Tom Rockwell, a geologist from San Diego State, pointed to a darker spot on the sand behind the fossil, indicating the path of the gully.

The water eroded one of the tusks and some of the bones. Agenbroad projects that the skeleton is still 75% to 85% intact. Scientists have found some fragments, including a piece of shoulder blade the size of a dinner plate, farther down the dune.

But the big discovery thus far has been the tusk. The two-foot-long extended tooth, made of the same substance as human teeth, survived for eons virtually intact.

Agenbroad has found nearly 100 tusks in a South Dakota sinkhole called the Mammoth Site, but has never excavated a pygmy mammoth.

From examining the tusk, Agenbroad began to speculate about the mammoth buried in the sand dune. He believes the animal was a male, about 40 years old. He also believes the pygmy variety descended from the Columbian mammoth, which he has found in South Dakota.

At some point, the mammoth swam to the Channel Islands, which were once one land mass about three to four miles off shore. After generations in the secluded spot, the species began to shrink--an evolutionary process common in island mammals.

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