For more than a decade, paleontologists have speculated about a single fossil that preserves skeletons of two of the world’s most famous dinosaurs, Tyrannosaurus rex and Triceratops. Not only are the bones arranged as they once were in life, but the dinosaurs are practically intertwined.Each specimen is among the best of its kind ever found. Together, the pair—nicknamed the “Dueling Dinosaurs”—present a paleontological mystery: Did the beasts just happen to be entombed together by chance, perhaps as carcasses caught on the same river sandbar? Or had they been locked in mortal combat? Nobody has been able to study the fossil to find out.