Washington ? 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 Tuesday 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 if “parts of it … were painted yesterday.”

The painting is the oldest intact mural ever found in Meso-America, dating to the Mayan “pre-Classic” period about 150 B.C. 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 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.”

The National Geographic Society has released a photo showing a detail from a Mayan mural found at San Bartolo in Guatemala. The mural depicts the birth of the cosmos and the divine right of a king, and this portion shows the son of the maize god, patron of kings, with a pair of birds tied to his woven hunting basket, letting blood and offering a sacrificed turkey before one of five cosmic trees, according to the society.

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.

The murals are accompanied by archaic Mayan writing just as sophisticated as later Classic glyphs that have been deciphered, but “the pre-Classic is a different system,” said Idaho State archaeologist Richard Hansen. “We can’t make sense of it until we have (more samples), but we’re getting into it.”