Anthropologists digging into an 8th century pyramid in Guatemala say they opened a tomb of what may be one of the last great leaders of the Mayan civilization.

Officials at Vanderbilt University announced Tuesday that a group led by Arthur Demarest, a professor of anthropology, removed the final loose stones under an ancient Mayan pyramid and found a skeleton wearing a bejeweled headpiece.Tracey Ferrell, the project administrator at Vanderbilt, said she talked briefly with Demarest and was told that the researchers found the skeleton amid elaborately decorated pottery and knife blades made of obsidian glass.

"It's definitely a ruler of some kind," Ferrell said. "Obsidian was an elite material in the Mayan world because it had to be brought from far away."

Obsidian is a volcanic glass. Knives made from the material were used in bloodletting ceremonies among the royalty, she said.

The pyramid is located in an ancient city known as Dos Pilas that is thought to have been the capital of the Petexbatun region of Guatemala. It is near the present city of Flores and the town of Sayaxche.

Demarest reported that the headdress adorning the skeleton was made of mother of pearl, shells and jade, and said to be in excellent condition.

Pottery in the tomb is covered in hieroglyphics that may give clues to the relationship of the Mayan center where the pyramid is situated and the rest of the Mayan civilization.

Ferrell said the skeleton may be that of a monarch known to researchers as Ruler 2. This name is used because no other has been found.

Demarest, who has been excavating in the area for two years, said in a report that the royal tomb was located on the edge of a great plaza and is near a monument, called Stela 8, that is dedicated to Ruler 2. The stela bears a date of A.D. 715.

"Ruler 2 was one of the kings that launched the ambitious program of conquest in the 8th century," Demarest reported. This led to formation of what he called the largest territorial state in Maya history. By A.D. 740, he said the kingdom started by Ruler 2 stretched for 1,500 square miles along the Pasion River.

Researchers believe the father of Ruler 2, known only as Ruler 1, was expelled from the Mayan city of Tikal a generation earlier. He went 60 miles into the jungle and established Dos Pilas.