Petroglyphs in the Colorado Plateau depict either Columbian mammoths or mastodons. A 13,000-year-old bone fragment from Vero Beach, Florida, possibly the earliest known example of art in the Americas, is engraved with either a mammoth or a mastodon. Some 11,000–13,000-year-old petroglyphs from the San Juan River in Utah are thought to include depictions of two Columbian mammoths; the mammoths' domed heads distinguish them from mastodons. They are also shown with two "fingers" on their trunks, a feature known from European depictions of mammoths. The tusks are short, which may indicate they are meant to be females. A carving of a bison (possibly the extinct "Bison antiquus") is superimposed on one of the mammoth carvings and may be a later addition. Other possible depictions of Columbian mammoths have been shown to be either misinterpretations or fraudulent.