The pyramid's proportions, along with smaller structures that were painted black and white, do not correspond to the Toltec or Teotihuacan cultures of the same area and time period.
The Teotihuacan people, who lived from 400 B.C. to A.D. 700, constructed one of the largest pyramid complexes in the pre-Hispanic Americas, which refers to cultures that lived on the continent before the Spanish conquest of the Western Hemipshere.
The Toltecs, who came afterward, were made up of several groups of South Americans that together formed an empire famous for its artists and builders in the Teotihuacan capital of Tula from A.D. 900 until the 1100s.
The pottery found at the site—rough, cylindrical vessels that are gray and reddish-brown in color—is also not familiar to experts.
(Related: "New Digs Decoding Mexico's 'Pyramids of Fire' [October 21, 2005].)
Based on the artifacts' discovery near the pyramid,"it is likely that the Huapalcalco pyramid has been built by people from this new culture," Hernández said.
Thomas Charlton, an archaeologist at University of Iowa, has worked in the state of Hidalgo.
He said that ample evidence—including the new artifacts—links a new pre-Hispanic culture to the Huapalcalco pyramid.
"It's a reasonable hypothesis [that] near the Valley of Tulancingo, there is a site that looks like it existed between the fall of the Teotihuacan and the beginning of the Tula [Toltec]," Charlton added.
"We know that there's an occupation [from this time] near Tulancingo.
"After the Teotihuacan, there were all sorts of smaller states throughout Mexico. It's part of the cycle after the fall of an empire."
Michael Smith, an archaeologist at Arizona State University, agreed.
"The notion that there would be an independent culture in [the Epiclassic] period is not surprising at all," he said.
"It was a very creative period, with rich development."
Future excavations of Huapalcalco should solidify the link to a new pre-Hispanic culture, and help archaeologists glean clues about this lost time, Hernández said.
"The [Epiclassic] period is considered a time of dynamic development—new trade, cities, and development," said Arizona State's Smith, "but one we don't know much about."
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