Photograph by Robert Clark
Weighted with a wooden frame that mimics a massive head and tail, University of Utah grad student Jason Otterstrom jumps and turns to test the agility of a creature like Allosaurus, a 150-million-year-old predator. "This experiment began as a joke," says comparative physiologist David Carrier, who supervised the experiment. "One of my students said, 'Let's just all dress up like Barney,' "the purple TV dinosaur. They discovered that a two-legged, two-ton (two-metric-ton) animal holding its tail horizontal couldn't have turned very fast. An arched tail, however, cut the rotational inertia by half. Time to redraw Allosaurus? Not just yet. Other scientists want more evidence.