WASHINGTON, May 15 -- An international team of researchers said Thursday they have identified a nearly complete skeleton belonged to a prehistoric teenage girl in an underwater Mexican cave, a discovery that could help resolve a longstanding debate about the origins of the first people to inhabit the Americas.

The skeleton of the girl, whom the team calls Naia Naia, which means "water nymph" in Greek, was found in 2007 in a large pit known as Hoyo Negro, Spanish for "Black hole," in Mexico's eastern Yucatan Peninsula, which was now reachable only by divers.

Her near-complete remains, with an intact cranium and preserved DNA, were surrounded by at least 26 large animals, including saber- toothed cats, giant ground sloths and elephant-like gomphotheres, the team reported in the U.S. journal Science.

The girl, about 15 or 16 years old, apparently fell into this cave and "died almost instantly, if not instantly" because her pelvis appears to have been broken at or around the time of her death, James Chatters, of Applied Paleoscience in Bothell, Washington, who led the study, told reporters .

"It appears that she fell quite a distance and struck something hard enough to fracture her pelvis," Chatters said. "It's possible she was looking for water because the Yucatan was extremely dry" during the time she lived.

According to the researchers, Naia's resting place, now 42 meters under water, would have become submerged during sea level rise between 9,700 and 10,200 years ago as global glaciers melted, long after Naia and the other extinct animals likely fell into it.

Based on radiocarbon dating of tooth enamel and analyses of mineral deposits on the bones of the girl, the researchers placed her age between 13,000 and 12,000 years ago, making her one of the six oldest humans yet found in the Americas. Yet, "she is certainly the most complete of this early group," Chatters said.

The girl possesses the unique skull and facial features of the earliest Americans, including "a much narrower, more projecting face, much wider set eyes, a more prominent forehead and nose," he said. These differ markedly from those of today's Native Americans, who tend to have broader and rounder skulls.

To understand more about her ancestry and its potential linkage to modern Native Americans, the researchers extracted DNA from her molars and the analysis showed that the ancient girl belonged to a genetic lineage that is shared only by Native Americans today.

The researchers said that the findings showed that Native Americans are descended from the earliest Paleoamericans, who moved onto the Bering Land Bridge, an area once above water between Siberia and North America, from northeast Asia between 26, 000 and 18,000 years ago, spreading southward into North America sometime after 17,000 years ago.

"This study therefore provides no support for the hypothesis that Paleoamericans migrated from Southeast Asia, Australia or Europe," study co-author Deborah Bolnick, assistant professor of anthropology at The University of Texas said.

"Instead, it shows that Paleoamericans could have come from Beringia (Bering Land Bridge), like contemporary Native Americans, even though they exhibit some distinctive skull and facial features."

The researchers said that the physical differences between Paleoamericans and Native Americans today likely arose not from separate origins but from evolution that occurred in Beringia and the Americas over the last 9,000 years.