MEXICO CITY (AFP) - Workers have discovered hundreds of bones belonging to Ice Age animals, including mammoths, mastodons and glyptodons, while digging to build a wastewater treatment plant north of Mexico City. The bones could be between 10,000 and 12,000 years old and may include a human tooth from the late Pleistocene period, Mexico's National Institute of Anthropology and History said on Thursday. Tusks, skulls, jawbones, horns, ribs, vertebrae and shells were discovered 20m deep in Atotonilco de Tula, a town in the state of Hidalgo, as workers built a drain, the institute said. These remains belong to a range of species including mastodons, mammoths, camels, horses, deer and glyptodons, the armadillo's ancestor. Some bones may belong to bison, while others have not been identified.