Tetanurae (/ˌtɛtəˈnjuːriː/ or "stiff tails") is a clade that includes most theropod dinosaurs, including megalosauroids, allosauroids, tyrannosauroids, ornithomimosaurs, maniraptorans, and 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 group was named by Jacques Gauthier in 1986 and originally had two main subgroups: Carnosauria and Coelurosauria, the clade containing birds and related dinosaurs such as compsognathids, tyrannosaurids, ornithomimosaurs, and maniraptorans. 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. Carnosauria has been reclassified as a group containing allosaurids that split from the Coelurosauria at the Neotetanurae/Avetheropoda node. Members of Spinosauroidea are believed to represent basal tetanurans.
Tetanuran evolution was characterized by parallel diversification of multiple lineages, repeatedly attaining large body size and similar locomotor morphology. Cryolophosaurus has been claimed as the first true member of the group, but subsequent studies have disagreed on whether it is a dilophosaurid or tetanuran. 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. Other tetanuran characterizing features include the absence of the fourth digit of the hand, placement of the maxillary teeth anterior to the orbit, a strap-like scapula, maxillary fenestrae, and stiffened tails. During the Late Jurassic and Early Cretaceous, large spinosaurids and allosaurs flourished but possibly died out in the northern hemisphere before the end of the Cretaceous, and were replaced as apex predators by tyrannosauroid coelurosaurs. At least in South America, carcharodontosaurid allosaurs persisted until the end of the Mesozoic Era, and died out at the same time the non-avian coelurosaurs.
|Skeleton of Monolophosaurus jiangi|
Avipoda Novas, 1992
Tetanurans have two basic skull morphologies. The first skull type, typical in large theropods such as Allosaurus, is common within ceratosaurs and may be primitive for tetanurans. In this type, the skull is about three times longer than tall, with a blunter snout and frequent elaborations such as horns or spikes along the lacrimals, nasals, and frontals. In the second skull type, the skull is lower and longer, with a less elaborated skull roof and a more elongated snout. Shared tetanuran features include the maxillary fenestra (an opening in the antorbital fossa), a pneumatic excavation in the jugal, and the position of the maxillary teeth anterior to the orbit. The posterior skull is little modified in tetanurans, except within Spinosauridae.
In the postcranial skeleton, tetanurans transition between the most primitive theropod morphologies in basal tetanurans towards more derived, bird-like states in coelurosaurs. Most tetanurans possess specialized wrist bones, the absence or reduction of the fourth digit of the hand, a strap-like scapula, stiffened tails, and a laminar astragalar ascending process. Advanced tetanurans would have possessed a sophisticated air-sac-ventilated lung system similar to birds, and an advanced circulatory system. In megalosaurids and allosaurids, the orientation of the femoral head is anteromedial such as in ceratosaurs, but in avetheropods this orientation is fully medial. Tetanuran locomotor morphology is relatively generalized, with few variations between taxa.
Basal tetanurans were the first theropod clade to achieve truly giant body sizes, with both megalosauroid and allosauroid taxa weighing over 1 ton. Sequential temporal appearances of large body size in subsequent clades suggest a pattern of size-cycles, with the extinction of incumbent giant forms allowing for replacement with a new, more bird-like theropod group that then also evolved giant body size. It is however possible that more than one giant tetanuran existed at a time in the same paleoenvironment, perhaps with feeding habit variations. Within most dinosaur clades, body size tended to increase over time along a lineage according to Cope’s Rule. Coelurosaurian theropods are the notable exception to the pattern of body size increases.
Tetanurae was recognized and named by Gauthier in 1986. The earliest discovered tetanuran is the earliest named dinosaur, Megalosaurus. For a century after the description of Megalosaurus, most large carnivorous dinosaurs were serially arrayed into the family Megalosauridae within the order Theropoda. In 1914, Friedrich von Huene separated small, lightly built forms into the infraorder Coelurosauria and larger taxa into the infraorder Pachypodosauria. Later, he transferred large, carnivorous taxa to the new infraorder Carnosauria, which came to include all known large-bodied carnivores other than Ceratosaurus. The size-based arrangement persisted until Gauthier, who redefined Carnosauria and Coelurosauria based on new cladistic analyses but retained the terms. Gauthier defined Coelurosauria as a taxon comprising birds and theropods closer to birds than to Carnosauria, and listed within Carnosauria several large-bodied theropod taxa but did not formally define the group. Many of these original carnosaurs have since been reclassified as coelurosaurs or primitive tetanurans, and Carnosauria has now been defined as Allosaurus and all Avetheropods closer to Allosaurus than to birds.
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.
Current phylogeny agrees on a monophyletic Tetanurae that includes a series of generally large-bodied basal taxa outside a monophyletic Coelurosauria. Coelophysoids are basal to Tetanurae, with Ceratosauria forming a sister taxa that diverged during the late Triassic.
After their initial appearance, Tetanurae radiated into two main clades, Spinosauroidea or Megalosauroidea and Avetheropoda or Neotetanurae. Spinosauroidea are believed to represent basal Tetanurans. At the Neotetanurae/Avetheropoda node, allosaurids split from the Coelurosauria. Tyrannosauridae has been placed within Coelurosauria. The allosaurids and their closest relatives form a reconstituted Carnosauria. Debate persists about whether the allosaurids form a clade with spinosauroids/megalosauroids, and whether Allosauroidea belongs in Avetheropoda with Coelurosauria or forms a sister taxa to Megalosauroidea, and whether Megalosauroidea forms a valid clade.
The biogeographical history of non-avian Tetanurae spans over 110 million years and all continents. The presence of major lineages prior to the breakup of Pangaea implies wide dispersal of these clades, with later absences indicating regional extinctions or dispersal failure. The density of sampling is currently insufficient to provide a detailed analysis of biogeographical evolution for the Tetanurae.
Tetanurae and Ceratosauria likely diverged during the late Triassic, more than 200 mya. By the Early Jurassic, Tetanurae fossils appear in the fossil record and reached global distribution by the Middle Jurassic. In the Late Jurassic, the fossil record demonstrates widespread presence of multiple clades within both megalosauroids and avetheropods. The Megalosauroidea contained high diversity with two Jurassic clades, Piatnitzkysauridae and Megalosauridae, as well as the Cretaceous Spinosauridae. Tetanuran evolution appears to exhibit waves of diversification, although this may be due to uneven sampling. During the Late Jurassic and Early Cretaceous, large spinosaurids and allosaurids flourished, but the latter possibly died out before the end of the Cretaceous due to the Cenomanian-Turonian boundary event, while spinosaurids are known from the Santonian. Soon afterwards the niche of terrestrial apex predator ceratosaurs and tyrannosaurid coelurosaurs, which dominated terminal Cretaceous terrestrial ecosystems. Coelurosaurs persisted through the end of the Mesozoic Era. Modern birds are the only living representatives of the Tetanurae.
Afrovenator (; "African hunter") is a genus of megalosaurid theropod dinosaur from the middle Jurassic Period of northern Africa.Averostra
Averostra, or "bird snouts", is a clade that includes most theropod dinosaurs that have a promaxillary fenestra (fenestra promaxillaris), an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw. Two groups of averostrans, the Ceratosauria and the Orionides, survived into the Cretaceous period. When the Cretaceous–Paleogene extinction event occurred, ceratosaurians and two groups of orionideans within the clade Coelurosauria, the Tyrannosauroidea and Maniraptoriformes, were still extant. Only one subgroup of maniraptoriformes, Aves, survived the extinction event and persisted to the present day.Chilesaurus
Chilesaurus is an extinct genus of herbivorous dinosaur. The type and only species is Chilesaurus diegosuarezi. Chilesaurus lived about 145 million years ago (Mya) in the Late Jurassic period of Chile. Showing a combination of traits from theropods, ornithischians, and sauropodomorphs, this genus has far-reaching implications for the evolution of dinosaurs, such as whether the traditional saurischian-ornithischian split is superior or inferior to the newly proposed group Ornithoscelida.Chuandongocoelurus
Chuandongocoelurus ( chwahn-DONG-ə-si-LEWR-əs) is a genus of carnivorous tetanuran theropod dinosaur from the Jurassic of China.Cruxicheiros
Cruxicheiros (meaning "cross hand") is a genus of tetanuran theropod dinosaur which lived in the Middle Jurassic of England. The type species is C. newmanorum, described by Roger Benson and Jonathan Radley in 2010.Cryolophosaurus
Cryolophosaurus ( or ; "CRY-oh-loaf-oh-SAWR-us") is a genus of large theropods known from only a single species Cryolophosaurus ellioti, known from the early Jurassic period of Antarctica. It was about 6.5 metres (21.3 ft) long and 465 kilograms (1,025 lb) in weight, making it one of the largest theropods of its time. Individuals of this species may have grown even larger, because the only known specimen probably represents a sub-adult. Cryolophosaurus is known from a skull, a femur and other material, the skull and femur of which have caused its classification to vary greatly. The femur possesses many primitive characteristics that have classified Cryolophosaurus as a dilophosaurid or a neotheropod outside of Dilophosauridae and Averostra, where as the skull has many advanced features, leading the genus to be considered a tetanuran, an abelisaurid, a ceratosaur and even an allosaurid. Since its original description, the consensus is that Cryolophosaurus is either a primitive member of the Tetanurae or a close relative of that group.
Cryolophosaurus possessed a distinctive "pompadour" crest that spanned the head from side to side. Based on evidence from related species and studies of bone texture, it is thought that this bizarre crest was used for intra-species recognition. The brain of Cryolophosaurus was also more primitive than those of other theropods.
Cryolophosaurus was first excavated from Antarctica's Early Jurassic, Sinemurian to Pliensbachian aged Hanson Formation, formerly the upper Falla Formation, by paleontologist Dr. William Hammer in 1991. It was the first carnivorous dinosaur to be discovered in Antarctica and the first non-avian dinosaur from the continent to be officially named. The sediments in which its fossils were found have been dated at ~194 to 188 million years ago, representing the Early Jurassic Period.Datanglong
Not to be confused with Datonglong, a hadrosauroid ornithopod dinosaur.
Datanglong is an extinct genus of carcharodontosaurian theropod belonging to the Tetanurae. It existed during the Early Cretaceous in what is now southeastern China.Dilophosauridae
Dilophosauridae is a family of medium to large sized theropod dinosaurs. The name Dilophosauridae is derived from Greek, with “di” meaning “two,” “lophos” meaning “crest,” “sauros” meaning “lizard,” and “idae” meaning “family”. While the name suggests that all dilophosaurids have two crests, this is not applicable to all dilophosaurids. The Dilophosauridae is anchored by the genus Dilophosaurus, and therefore the name comes from the distinctive two crests of the genus.Gasosaurus
Gasosaurus (Chinese: 气龙属) () is a genus of tetanuran theropod that lived approximately 171.6 to 161.2 million years ago during the middle of the Jurassic Period. The name "Gasosaurus" is derived from the English "gasoline" and the Greek σαῦρος/sauros ("lizard / generic reptile"). Only one species is currently recognised, G. constructus, from which the specific name honours the gasoline company that found the Dashanpu fossil quarry in Sichuan Province, China, now named as the Lower Shaximiao Formation.Iliosuchus
Iliosuchus (meaning "crocodile hipped") is a genus of theropod dinosaur known from Bathonian–age (168.3 – 166.1 mya) rocks of England. It was perhaps 1.5 metres (4.9 ft) long.The only known fossils of this genus are three ilia (BMNH R83, OUM J29780 and OUM J28971) from Stonesfield Slate, Oxfordshire, England. From the holotype BMNH R83, Friedrich von Huene described and named the only species, I. incognitus, in 1932. The generic name is derived from the ilium and Greek Souchos, the crocodile god. The specific name means "unknown" in Latin. Another species, I. clevelandi, was proposed in 1976 by Peter Galton, who assigned Stokesosaurus clevelandi to Iliosuchus, but this has not been followed.
The Iliosuchus ilia, very small with a length of nine to ten centimetres, have a vertical supra–acetabular ridge on the surface, similar to tyrannosaurids and many other predatory dinosaurs belonging to the group Tetanurae, including Piatnitzkysaurus and Megalosaurus. Such fargmentary and incomplete material is inadequate for accurate classification; nonetheless, Iliosuchus has sometimes been considered a tyrannosaurid ancestor. This is unlikely to be correct as the bones cannot be distinguished from small individuals of Megalosaurus, a megalosaurid. Whatever the case, Iliosuchus is not diagnostic and is therefore dubious. If Iliosuchus incognitus is a tyrannosauroid, it would be a possible ancestor to Proceratosaurus, the earliest recognized tyrannosauroid, and would be the earliest of the tyrannosauroid family tree.Kaijiangosaurus
Kaijiangosaurus (meaning "Kiijiang lizard") is a genus of carnivorous tetanuran theropod dinosaur from the Middle Jurassic of China. In 1984 He Xinlu named and described the type species Kaijiangosaurus lini. The generic name refers to the River (jiang) Kai. The specific name honours the paleontologist Lin Wenqiu.Kayentavenator
Kayentavenator (meaning "Kayenta hunter") is a small carnivorous dinosaur genus which lived during the Early Jurassic Period; fossils were recovered from the Kayenta Formation of northeastern Arizona and were described in 2010.Lepidus praecisio
Lepidus is a genus of extinct coelophysoidean theropod from the Upper Triassic of the United States. It lived in the Otis Chalk localities of the Dockum Group in Texas, around 223 million years ago.Megalosauroidea
Megalosauroidea (meaning 'great/big lizard forms') is a superfamily (or clade) of tetanuran theropod dinosaurs that lived from the Middle Jurassic to the Late Cretaceous period. The group is defined as Megalosaurus bucklandii and all taxa sharing a more recent common ancestor with it than with Allosaurus fragilis or Passer domesticus. Members of the group include Spinosaurus, Megalosaurus, and Torvosaurus.Monolophosaurus
Monolophosaurus ( MON-o-LOF-ə-SAWR-əs; meaning "single-crested lizard") is a genus of tetanuran theropod dinosaur from the Middle Jurassic Shishugou Formation in what is now Xinjiang, China. It was named for the single crest on top of its skull. Monolophosaurus was a mid sized theropod at about 5 metres long.Neotheropoda
Neotheropoda (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and the only group of theropods who survived the Triassic–Jurassic extinction event. Yet all of the neotheropods became extinct during the early Jurassic period except for Averostra.Orionides
Orionides is a clade of tetanuran theropod dinosaurs from the Middle Jurassic to the Present. The clade includes most theropod dinosaurs, including birds.Theropoda
Theropoda ( or , from Greek θηρίον "wild beast" and πούς, ποδός "foot") or theropods () are a dinosaur suborder that is characterized by hollow bones and three-toed limbs. They are generally classed as a group of saurischian dinosaurs, although a 2017 paper has instead placed them in the proposed clade Ornithoscelida as the closest relatives of the Ornithischia. Theropods were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores, omnivores, piscivores, and insectivores. Theropods first appeared during the Carnian age of the late Triassic period 231.4 million years ago (Ma) and included the sole large terrestrial carnivores from the Early Jurassic until at least the close of the Cretaceous, about 66 Ma. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are today represented by about 10,500 living species.Thomas R. Holtz Jr.
Thomas Richard Holtz Jr., Ph.D. is an American vertebrate palaeontologist, author, and principal lecturer at the University of Maryland's Department of Geology. He has published extensively on the phylogeny, morphology, ecomorphology, and locomotion of terrestrial predators, especially on tyrannosaurids and other theropod dinosaurs. He wrote the book Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages and is the author or co-author of the chapters "Saurischia", "Basal Tetanurae", and "Tyrannosauroidea" in the second edition of The Dinosauria. He has also been consulted as a scientific advisor for the Walking With Dinosaurs BBC series as well as the Discovery special When Dinosaurs Roamed America, and has appeared in numerous documentaries focused on prehistoric life, such as Jurassic Fight Club on History and Monsters Resurrected on Discovery.Holtz is also the director of the Science and Global Change Program within the College Park Scholars living-learning community at the University of Maryland, College Park.