Troodontids were slender, fast-moving theropods rarely more than two meters long, but their skulls stand out disproportionately: brain cavities large relative to body size even by dinosaur standards, and large, forward-facing eye sockets that suggest strong binocular vision and, in some genera, the possibility of low-light or nocturnal hunting. Their jaws carried finely serrated teeth suited to a mixed diet of small prey and possibly plant material.
The family is known from the Late Jurassic through the very end of the Cretaceous, mostly from North America and Mongolia. Troodon itself was long a taxonomically contentious genus, named from isolated teeth before more complete material clarified the family's anatomy; Saurornithoides, from Mongolia, is another well-documented member. Troodontids are frequently cited in discussions of dinosaur intelligence and are considered close relatives of the theropod lineage that gave rise to birds.