Tetanurae

Tetanurae, meaning "stiff tails," is a large clade of theropod dinosaurs that includes most predatory dinosaur diversity, encompassing the megalosauroids, the allosauroids, and the coelurosaurs, the last of which contains tyrannosauroids, ornithomimosaurs, compsognathids, and the maniraptorans, including living birds. The group is defined as all theropods more closely related to modern birds than to Ceratosauria (Gauthier, 1986), its sister lineage, from which it diverged during the Late Triassic according to Sereno and colleagues (1994). Tetanurans appear in the fossil record by the Early Jurassic and had become globally distributed by the Middle Jurassic. Their evolution was marked by the parallel diversification of several lineages that repeatedly attained large body size and similar locomotor forms; basal members were the first theropods to reach truly giant sizes, with some megalosauroids and allosauroids exceeding a ton. Distinctive features of the group include stiffened tails, the loss of the fourth finger to leave a three-fingered hand, maxillary teeth restricted to the front of the snout, and, in more advanced forms, an air-sac-ventilated lung system resembling that of modern birds. Birds are the only living survivors of the clade.