Jack Horner, Curator of Paleontology at Museum of the Rockies, provides scale for Tyrannosaurus rex fossils at excavation site near the Fort Peck Reservoir, Fort Peck, Mont., June 1990. Named for its discoverer, Kathy Wankel, the Wankel T.rex is estimated to have weighed six to seven tons. (Photo by Museum of the Rockies)