Archaeologists have uncovered an elegantly painted 30-foot-long mural in a ceremonial chamber beneath a Guatemalan jungle pyramid, providing new evidence that Mayan civilization was in full flower more than 2,000 years ago.

Archaeologist William Saturno of the University of New Hampshire and Harvard's Peabody Museum of Archaeology and Ethnology said yesterday that the San Bartolo site, in Guatemala's Peten wilderness, is "the find of a lifetime," depicting the Mayan creation myth and the crowning of a king in vivid color on a plaster wall as though "parts of it . . . were painted yesterday."

Guatemalan archaeologist Monica Pellicer Alecio, with project director William Saturno, explores the oldest known Mayan royal tomb, dating from about 150 B.C. (Photos By Kenneth Garrett -- National Geographic)

The painting is the oldest intact mural ever found in Meso-America, dating to about 150 B.C. in the Mayan "pre-classic" period. But the subject matter has the same breadth of mythology and cultural complexity as that displayed at "classical" Mayan sites nearly 500 years later.

"This verifies what we had long suspected -- that Mayan civilization had crystallized by the time" the San Bartolo site arose, said University of Pennsylvania archaeologist Robert J. Sharer, author of "The Ancient Maya." "The institution of divine kingship is in place -- the imagery is consistent with later times. It's a terrific find."

Saturno discovered San Bartolo in 2001 when he took refuge from the tropical heat by ducking into a looters' trench cut into the back of a jungle-covered pyramid in northern Guatemala, near the Mexican border. He found himself inside a chamber choked with landfill. But the north wall revealed a four-foot-long swath of beautifully preserved mural depicting the resurrection of the Corn God, a scene from Mayan creation myth.

"As spectacular as this was," Saturno said during a telephone news conference organized by the National Geographic Society, "we knew that the west wall was more than twice its length and was the centerpiece of the ancient room."

And so it proved. The 30 feet of west wall mural, the excavation of which began in 2004, shows the son of the Corn God establishing land, water and air, and paradise in the east where the sun rises. The next section shows the Corn God's coronation, followed by death and resurrection. The last section shows the coronation of a Mayan king, claiming his crown in the company of the gods.

While the north wall was painted in black, red, yellow and pink, the west wall added several shades of blue, white, and dark and light gray. "The murals were painted at the same time, but there's more than one artistic hand," Saturno said. National Geographic magazine is profiling San Bartolo in next month's issue.

Three doors into the chamber were on the now-destroyed east wall, making the west wall the first and most arresting sight for new arrivals. "Our best guess is that this was a preparation room, where the king would rehearse the mythology for ceremonies" outdoors, Saturno said.

The murals are accompanied by archaic Mayan writing as sophisticated as later classic glyphs that have been deciphered, but "the pre-classic is a different system," said archaeologist Richard D. Hansen of Idaho State University. "We can't make sense of it until we have [more samples], but we're getting into it."

The murals, three feet tall and painted on layers of plaster smoothed over foundation stone, survived for centuries in the coolness beneath the pyramid, with the chamber filled with earth containing thousands of mural fragments from the east and south walls.

About a mile from the pyramid, a team led by Guatemalan archaeologist Monica Pellicer Alecio in 2004 began excavating a vaulted tomb containing a man's remains and a large jade plaque, the symbol of Mayan royalty.

Saturno said the story told by the murals and the presence of a nearby royal burial site demonstrate a fully developed Mayan political hierarchy in a relatively small place at a time when the area was probably dominated by the large city of El Mirador about 60 miles away.

"But it's all there in San Bartolo too," said Hansen, an El Mirador specialist. "The pre-classic was a complex and sophisticated society, and this is the greatest compilation of murals ever found in Meso-America. It's a wonderful opportunity for scholars."