One of Knight 's best-known pieces for the American Museum of Natural History is 1897 â s Leaping Laelaps , one of the few pre-1960s images to present dinosaurs as active , fast-moving creatures . This was long before the theories of modern paleontologists like Robert Bakker . One of Knight 's best-known pieces for the American Museum of Natural History is 1897 â s Leaping Laelaps , which was one of the few pre-1960s images to present dinosaurs as active , fast-moving creatures ( thus anticipating the theories of modern paleontologists like Robert Bakker ) .