coelurosaur

Coelurosaur is a major clade of theropod dinosaurs within the group Tetanurae. It is defined as all theropods more closely related to Coelurus than to Allosaurus. Members of this group encompass a wide range of sizes and forms and include several well-known subgroups, such as Tyrannosauroidea (tyrannosaurs), Ornithomimosauria (ostrich-like dinosaurs), and the maniraptoriformes, which lead to dromaeosaurs, troodontids, and birds. The fossil record shows coelurosaurs from the Late Jurassic onward, with a major diversification during the Cretaceous.

Coelurosaurs are characterized by various evolutionary trends that distinguish them from other theropods, including lighter skulls and skeletons, more specialized hands and wrists, and in many lineages the development of feathers. Feathers are known from numerous coelurosaur fossils and are considered a common feature of the group, with some lineages giving rise to flight-adapted forms. Size within the clade ranges from small, about one meter in length, to very large tyrannosaurids.

Ecology and diversity within Coelurosauria were broad. Dietary habits ranged from carnivory to omnivory, with apex predators among the tyrannosaurids and a variety of smaller, more opportunistic forms elsewhere. The clade achieved a near-global distribution, with fossils recovered from multiple continents. Living coelurosaurs are birds, which are now understood to have descended from small theropod ancestors within this lineage, possessing feathers, hollow bones, and other avian features.