Crews at the Ice Age fossil dig site near Snowmass Village have uncovered bones from an Ice Age horse.The workers found a horse ankle bone at the very bottom layer of the Ice Age lake site.Officials said that makes the horse one of the oldest animals at the site.Excavation began at the site last fall after a bulldozer operator uncovered a bone while working on an expansion of Ziegler Reservoir. Work stopped for the winter, but resumed in mid-May.Horses were common in North America during the Ice Age and disappeared from North America about 12,000 years ago.In the last week, crews have also found a large number of Jefferson ground sloth bones, as well as claws and a complete skull. It is the first complete sloth skull discovered at the site. Chris Faison, a teacher at Aspen Community School, found the skull.Crews have found more than 2,300 fossils that have been uncovered this spring. Crews are scheduled to dig at the site until July 1, when the site will be handed back over to the water district and work on the expanded reservoir will be completed.A small excavation crew will remain on site.Get the latest on the project on the Denver Museum of Nature & Science's Snowmastodon Project website. .