## T. rex teeth indicate it ran as warm as an elephant Isotope ratios provide a hint that the giants were actively managing temperatures. For most of the last century, T. rex was pictured as a sluggish, tail-dragging reptile that had to warm up in the sun before it could go anywhere. Then, further research changed that view, replacing it with the active, bird-like animal shown in the movie Jurassic Park. But whether T. rex used warm blood to power that activity remained a question. Now we might have gotten closer to an answer. A team of researchers led by Randon J. Flores and Robert A. Eagle,…