Tetanurae (; meaning "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, and coelurosaurs (which includes tyrannosauroids, ornithomimosaurs, compsognathids and maniraptorans, the latter including living birds). Tetanurans are defined as all theropods more closely related to modern birds than to Ceratosaurus and contain the majority of predatory dinosaur diversity. Tetanurae likely diverged from its sister group, Ceratosauria, during the late Triassic. Tetanurae first appeared in the fossil record by the Early Jurassic about 190 mya and by the Middle Jurassic had become globally distributed. The original Carnosauria was a polyphyletic group including any large carnivorous theropod. Many of Gauthier's carnosaurs, such as tyrannosaurids, have since been re-classified as coelurosaurs or primitive tetanurans. Arcucci and Coria (2003) classified Zupaysaurus as an early tetanuran, but it was later placed as a sister taxon to the clade containing dilophosaurids, ceratosaurs, and tetanurans.
Shared tetanuran features include a ribcage indicating a sophisticated air-sac-ventilated lung system similar to that in modern birds. This character would have been accompanied by an advanced circulatory system. At least in South America, carcharodontosaurid allosaurs may have persisted until the end of the Mesozoic Era, and died out at the same time as the non-avian coelurosaurs.
Morphology
thumb|left|Illustration of [[Monolophosaurus jiangi]]
Anatomy
Tetanurans have two basic skull morphologies.
Body Size
Basal tetanurans were the first theropods to achieve truly giant body sizes, with both megalosauroid and allosauroid taxa weighing over 1 ton. Coelurosaurian theropods are the notable exception to the pattern of body size increases. The earliest-discovered non-avian tetanuran is Megalosaurus.
Initial cladistics studies supported the arrangement of primitive megalosaurs as serial outgroups to a clade of allosaurids, followed by the Coelurosauria. Subsequent studies have discovered that many of these basal tetanurans formed a true clade, termed Megalosauroidea or alternatively Spinosauroidea. In 2015, Hendrickx, Hartman and Mateus clarified this definition, specifying it as the least inclusive clade including Allosaurus fragilis, Megalosaurus bucklandii, and Passer domesticus.
The clade name "Orionides" was first established by Matthew T. Carrano, Roger B. J. Benson and Scott D. Sampson in 2012. It is derived from Orion, the giant hunter of Greek mythology in references to the large size and carnivorism of basal orionidans. The name also refers to the alternative name for the constellation of Orion, Alektropodion, meaning "rooster foot". and was first defined as a clade by Currie and Padian in 1997, to include Allosaurus, modern birds, and other animals descended from their most recent ancestor. In 1999, Paul Sereno named another group, Neotetanurae, for the clade containing Allosauroidea and Coelurosauria, and excluding other tetanurans such as megalosauroids, but this definition was published slightly later.
A monophyletic Avetheropoda is recovered in many papers; however, recent findings suggest a monophyletic Carnosauria model with allosauroids and megalosauroids as each other's closest relatives instead of Allosauroids and Coelurosaurs.
The cladogram presented below follows a phylogenetic analysis published by Zanno and Makovicky in 2013.
Paleobiology
Biogeography
The biogeographical history of non-avian Tetanurae spans over 110 million years and all continents.