Origin of birds
The group most favoured as ancestral is the Paraves or Eumaniraptora, which includes the dromaeosaurs and the troodonts. The dromaeosaurs include Velociraptor and Deinonychus but, of course, it would have been an earlier type of dromaeosaur, perhaps from the lower Jurassic. Dromaeosaurs have several traits we used to think were special to birds: hollow bones with holes for air-sacs, limbs with many bones either lost or fused, clavicles fused into wishbones, and feathers.