Tetanurae

Tetanurae is a major clade of theropod dinosaurs that includes the majority of species traditionally considered carnivorous theropods, most notably the lineage that led to birds. It is defined phylogenetically as all theropods more closely related to birds than to Ceratosaurus. The name, from Greek for “stiff tail,” reflects the early association of a stiffened tail with the group, though this feature is not universal among all its members.

Origin and evolution: Tetanurae first appears in the fossil record by the Late Triassic to Early Jurassic, with the earliest clearly identifiable members in the Middle to Late Jurassic. The clade diversified widely during the Jurassic and Cretaceous, giving rise to a broad spectrum of forms ranging from large apex predators to the diverse small-bodied theropods that later produced birds.

Classification and diversity: Within Tetanurae, two major lineages are Megalosauroidea and Coelurosauria. Megalosauroidea includes several early large theropods and is commonly associated with taxa such as Megalosaurus and Torvosaurus; in many modern classifications, Spinosauridae is placed within Megalosauroidea. Coelurosauria is a large, diverse group that includes Tyrannosauroidea, Ornithomimorpha, the therizinosaurs, and the Maniraptora, the latter of which culminates in the true birds (Aves).

Significance: Birds are the only living descendants of Tetanurae, making the clade central to studies of avian evolution and the broader history of theropod dinosaurs. The group encompasses a wide range of ecologies and morphologies across deep time.