GUATEMALA CITY — Archaeologists have found an “extraordinary” Mayan frieze richly decorated with images of deities and rulers and a long dedicatory inscription, the Guatemalan government said Wednesday.

The frieze was discovered by Guatemalan archaeologist Francisco Estrada-Belli, a professor at Tulane University’s Anthropology Department, and his team in the northern Province of Peten, the government said in a joint statement with Estrada-Belli....