Desc: Bizarre Dinosaurs: Directed by Jenny Kubo. With Jack Horner, Paul Sereno, Gregory Erickson, Robert Bakker. As dinosaurs grew into the behemoths of the Cretaceous period they evolved many extraordinary but apparently useless features including spikes, sails horns, crests and the tiny "arms" of tyrannosaurs. The program reviews these unusual features and discusses theories of why they exist.