LOS ANGELES – A complete tusk believed to belong to a prehistoric mammoth was uncovered on Santa Cruz Island off the Southern California coast, researchers reported Tuesday. If the discovery is confirmed, it would mean the tusked beasts roamed 62,000-acre Santa Cruz Island more widely than previously thought.

A graduate student at the University of California, Santa Barbara, came across the tusk while working in a canyon on the island's remote north shore earlier this month. Nearby were several rib bones and possible thigh bones, said Lotus Vermeer, the Nature Conservancy's Santa Cruz Island project director.

"We've never discovered mammoth remains in this particular location on this island before," Vermeer said.

The Nature Conservancy and a leading mammoth expert will excavate the remains next week and use radiocarbon dating to determine their age.

Santa Cruz Island is the largest of eight islands that make up California's Channel Islands. During the Pleistocene epoch, more than 10,000 years ago, the four northern islands — Santa Cruz, San Miguel, Santa Rosa and Anacapa — formed one big island that scientists call Santarosae.

Scientists theorized that mainland Columbian mammoths — ancestors of the present-day elephant — swam across the channel in search of vegetation on Santarosae. Over time, they evolved into a pygmy form to better adapt to scarce resources on the islands.

Judging by the tusk size — about 4 feet long — it might have belonged to a pygmy mammoth, Vermeer said.

The most complete skeleton of a prehistoric pygmy mammoth was excavated in 1994 on Santa Rosa Island. It's rare to find mammoth remains on Santa Cruz Island, probably because its steep terrain was inhospitable to pygmy mammoths.

In 2005, researchers discovered mammoth thigh and forelimb bone fragments on Santa Cruz. Ten years earlier, a partial tusk was unearthed. Both discoveries were from a Columbian mammoth.

Paul Collins, curator of vertebrate zoology at the Santa Barbara Museum of Natural History, was unsure of the significance of the latest find based on pictures he has seen. Collins said it was possible the remains could have belonged to a marine mammal and said an excavation should settle the matter.

"It's very difficult to tell whether or not you're dealing with mammoth bones," he said.

• Re: Mammoth Tusk Found on Santa Cruz Island Jim 09:41:45 01/14/09 (0)