CARLSBAD: Giant sloth skeleton uncovered

By RUTH MARVIN WEBSTER - Staff Writer | Monday, April 14, 2008 4:32 PM PDT ∞

CARLSBAD -- Another Ice Age treasure -- this time the skeleton of a giant sloth -- has been unearthed at a Carlsbad construction site, officials said Monday.

The find is the most complete sloth skeleton ever discovered in San Diego County, said Tom Demere, the curator of paleontology at the San Diego Natural History Museum.

The skeleton emerged late last month during grading at the Robertson's Ranch project in east Carlsbad, where the remains of a prehistoric mastodon were uncovered in June.

The giant sloth -- about the size of a cow -- is believed to have roamed North County more than 11,000 years ago, walking on its knuckles and grazing on vegetation along the ancient lake that is now Agua Hedionda Lagoon.

Demere said he and his staff couldn't be more pleased with the recent find.

"We have a list of most wanted fossils for each time period," he said, "Even though it's not complete, it is going to definitely satisfy our longing for the Pleistocene."

Demere said the skeleton found in Carlsbad is probably that of a Shasta Ground Sloth (Nothrotheriops shastensis). Although the smallest of the North American ground sloths, the species was about 7 to 8 feet long and weighed between 300 and 400 pounds.

According to the American National Museum, the animal's range stretched the length of North America, but disappeared between 10,000 to 11,000 years ago with the end of the Great Ice Age.

"They were probably the first victims of global warming," Demere said.

He said he believes that archeologists in Carlsbad have found the pelvis/hip area of the sloth, portions of one front limb and one hind limb, as well as some ribs. The find may also include the remains of the animal's rather small head.

He said the when the sloth was uncovered, the bones and surrounding soil were set in plaster at the site and then transported to the Natural History Museum warehouse where they will dry out a bit.

"These bones are very soft and very fragile, " Demere said.

Once the plaster jacket has dried out sufficiently, the bones will be examined by the musuem's preparation lab manager, Maggie Hart Carrino, Demere said. Carrino will prepare the fossils by carefully peeling off the plaster to expose the hardened the bones.

The discovery is one of hundreds of fossils that have been found over the last several years in the remarkably fossil-rich area of Carlsbad.

In June, the upper and lower jaws, tusks, rib fragments, teeth and a vertebra of another Ice Age land mammal, the mastodon, was found in the same general area.

Demere said the sloth fossil may be put on display at the natural museum in the future or at the Agua Hedionda Lagoon Discovery Center, which displayed fossils from the prehistoric mastodon in March.

Contact staff writer Ruth Marvin Webster at (760) 901-4074 or rwebster@nctimes.com.

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