Deinonychus — the dinosaur that rewrote what "bird" means

When and where

Deinonychus lived from 115 to 108 million years ago, during the Early and late Cretaceous. Its fossils come from Montana, Utah, Wyoming, and Oklahoma in the western United States, preserved in the Cloverly and Antlers formations. At the time, this region held broad river systems and seasonal floodplains, with conifers and ferns dominating the vegetation. Some teeth possibly belonging to Deinonychus have also turned up in Maryland, much farther east.

How we know

Paleontologist John Ostrom described Deinonychus in 1969, basing the name on a partial skeleton from Montana. The name means "terrible claw," referring to the enlarged, sickle-shaped claw on each second toe. Before Ostrom's work, dinosaurs were widely seen as sluggish and cold-blooded. Deinonychus changed that. Its light, hollow bones and the clear adaptations for fast movement suggested an active, possibly warm-blooded animal far closer to a modern bird in physiology than to a modern reptile. This line of argument became one of the foundations of the dinosaur renaissance. Source: Wikipedia.

What set it apart

Deinonychus reached about 3.4 metres long and stood roughly hip-high to a human. Its body was slim, with a long balancing tail stiffened by bony rods. The jaw held dozens of curved, serrated teeth, and each foot carried a retractable sickle claw up to 13 centimetres long. The arms were long and likely feathered, though direct skin impressions are not known. Ostrom argued that Deinonychus hunted in packs, based on the association of several individuals with a single large herbivore skeleton. That idea remains debated, but the image of coordinated, fast predators stuck. It is the best-known member of the dromaeosaurid family, the group that also includes Velociraptor.

For collectors and classrooms

A Deinonychus figurine is useful for showing the shift in thinking about dinosaurs. Look for a model that gets the sickle claw right, the long tail, and the slightly horizontal posture. It pairs well with a Velociraptor model in a classroom display, since the two families share the same basic plan but lived on opposite sides of the world. Find a hand-painted figurine here.