Coelurosaurs

Coelurosaurs are a major clade of theropod dinosaurs within the larger group Theropoda. The clade includes tyrannosauroids, ornithomimids, compsognathids, and the diverse Maniraptora, which further encompasses dromaeosaurids, troodontids, oviraptorosaurs, therizinosaurs, and birds. Phylogenetically, Coelurosauria is defined as all theropods more closely related to Coelurus than to Carnotaurus, a definition that places birds within the group.

Coelurosaurs first appear in the Middle Jurassic and become widespread in the Late Jurassic and Cretaceous. They show a wide range of sizes and ecologies, from small, agile hunters to gigantic predators. Notable subgroups include the small, fast compsognathids; the fast-running ornithomimids; and the diverse maniraptorans, which include feathered forms with raptorial forelimbs and specialized beaks.

Morphology and biology: Many coelurosaurs bear feathers or feather-like coverings, and some skeletal features indicate adaptations for active growth and increased metabolic rates. Among non-avian coelurosaurs, dinosaurs such as dromaeosaurids and troodontids display advanced grasping hands and sharp teeth or beaks in various lineages; therizinosaurs are unusually long-necked and herbivorous. The range of diets includes carnivory, omnivory, and herbivory.

Significance: Birds are the only surviving coelurosaurs, representing the living lineage that emerged from this group. The coelurosaur fossil record documents the evolution of flight-related features and diverse predatory and locomotor adaptations.