Scientists say an excavation site near Aspen has unearthed fossils for ice age mastodons of all ages. The Denver Museum of Nature & Science said Friday they've found the skull of an infant mastodon, the skull of a juvenile, and the thigh bone of what may have been a fetus. The skulls range in size from a basketball to a beer keg. Scientists have also discovered 26 mastodon tusks, indicating that there were at least 13 to 20 different mastodons at the Snowmass Village site. Researchers say there have only been three other mastodon fossils found in Colorado until now. They've said they can only speculate why so many bones have been found at the excavation site, which used to be a lake bed.