Ostrom's Deinonychus and the Dinosaur Renaissance

In 1969 John Ostrom of Yale described Deinonychus antirrhopus, found with Grant Meyer in the Cloverly Formation of Montana in 1964. It was about 3 m long and 70 kg, with a stiffened tail, grasping hands and a sickle-shaped claw about 12 cm long on each second toe. Ostrom argued that its design meant an agile, active hunter, not the sluggish swamp-bound reptile that textbooks still showed. Several Deinonychus lay near the bones of a larger plant eater, Tenontosaurus, which led him to suggest pack hunting, a claim that is still argued.¹²

Ostrom then went back to Archaeopteryx, studying the Teylers Museum specimen in Haarlem, which had been mislabeled as a pterosaur, and concluded that Archaeopteryx and Deinonychus shared many features. This revived Thomas Huxley's old claim that birds descend from small meat-eating dinosaurs. His student Robert Bakker pushed the case for warm-blooded, active dinosaurs in a 1975 article titled The Dinosaur Renaissance in Scientific American.¹⁵

The theory shifted the field in less than two decades. Dinosaurs became fast, social, sometimes feathered animals, and birds became living dinosaurs. The Liaoning feathered dinosaurs in the 1990s confirmed it. Michael Crichton later used Deinonychus as the model for Jurassic Park's raptors, though he used the name Velociraptor. Museums began to re-pose skeletons upright and active, with the tail held out for balance instead of dragging.¹³⁴