Temporal range: Jurassic–Cretaceous
|Deinonychus (large) and Buitreraptor (small), Field Museum of Natural History|
Colbert & Russell, 1969
The Deinonychosauria ("fearsome claw lizards") is a clade of bird-like theropods in the Upper Jurassic and Cretaceous. The largest known of these was Utahraptor, and Anchiornis was the smallest. The group includes two rather different families. Each of these is described more fully on its own page.
Troodontids date from the Upper Cretaceous and were lighter and slimmer than the dromaeosaurids. Troodon and Saurornithoides are two examples. As a group, they are closely related to birds. Troodontids had unusually large brains, comparable to living flightless birds. Their eyes were also large, and pointed forward, so they had good binocular vision. A few troodont fossils, including specimens of Mei and Sinornithoides, show that these animals roosted like birds, with their heads tucked under their forelimbs. They were fully feathered.