Theropoda

{{Short description|Extant clade of dinosaurs}} {{Distinguish|text=Pteropoda, marine gastropods}} {{pp-pc}} {{pp-pc|small=yes}} {{use dmy dates|date=June 2024}} {{Automatic taxobox | name = Theropoda | taxon = Theropoda | authority = Marsh, 1881 | fossil_range = <br/>Late Triassic – present, including birds {{fossilrange|233.2|0}} | image = {{Multiple image | perrow = 2/2/2 | total_width = 330 | caption_align = center | image1 = Carnotaurus skeleton in Bonn White Background.jpg | image2 = Coelophysis (1) white background.jpg | image3 = Stan T. rex in Oslo white background.jpg | image4 = Irritator challengeri mount 01 white background.jpg | image5 = Struthiomimus white background.JPG | image6 = Archaeopteryx Philadelphia white background.jpg | footer = Gallery of theropods (clockwise from top left) ''Carnotaurus'', ''Coelophysis'', ''Irritator'', ''Archaeopteryx'', ''Struthiomimus'' and ''Tyrannosaurus'' | border = infobox }} | subdivision_ranks = Subgroups | subdivision_ref = <ref name=Holtz2008>{{cite book |last=Holtz |first=Thomas R., Jr. |date=Winter 2011 |section=Appendix |title=Dinosaurs: The most complete, up-to-date encyclopedia for dinosaur lovers of all ages |section-url=http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf |publication-date=2012 }}</ref> | subdivision = *{{extinct}}''Anteavis'' * {{extinct}}''Eodromaeus'' * {{extinct}}''Erythrovenator'' * {{extinct}}''Tawa'' * {{extinct}}''Velocipes'' * '''Neotheropoda''' <small>Bakker, 1986</small> **{{extinct}}'''Coelophysoidea''' **'''Averostriformes''' <small>Wang et al., 2026</small> *** {{extinct}}''Chuandongocoelurus'' *** {{extinct}}''Cryolophosaurus'' *** {{extinct}}''Dilophosaurus'' *** {{extinct}}''Dracovenator'' *** {{extinct}}''Notatesseraeraptor'' *** {{extinct}}''Sarcosaurus'' *** {{extinct}}''Sinosaurus'' *** {{extinct}}''Spinostropheus'' *** {{extinct}}''Tachiraptor'' *** {{extinct}}''Zupaysaurus'' ***'''Averostra''' <small>Paul, 2002</small> **** {{extinct}}'''Ceratosauria''' **** '''Tetanurae''' {{collapse top|title=Theropods of uncertain affinity |left=yes|padding=0|border=0|border2=0|bg=clear|bg2=clear}} * {{extinct}}''Austrocheirus'' * {{extinct}}''Bahariasaurus'' * {{extinct}}''Camarillasaurus'' * {{extinct}}''Chilantaisaurus'' * {{extinct}}''Coeluroides'' * {{extinct}}''Compsosuchus'' * {{extinct}}''Dandakosaurus'' * {{extinct}}''Deltadromeus'' * {{extinct}}''Dornraptor'' * {{extinct}}''Gojirasaurus'' * {{extinct}}''Gualicho'' * {{extinct}}''Kakuru'' * {{extinct}}''Labocania'' * {{extinct}}''Newtonsaurus'' * {{extinct}}''Orthogoniosaurus'' * {{extinct}}''Ostafrikasaurus'' * {{extinct}}''Ozraptor'' * {{extinct}}''Shuangbaisaurus'' * {{extinct}}''Szechuanosaurus'' * {{extinct}}''Wakinosaurus'' * {{extinct}}''Xuanhanosaurus'' {{Collapse bottom}} {{Collapse top|title=Possible theropods |left=yes|padding=0|border=0|border2=0|bg=clear|bg2=clear}} * {{extinct}}''Alwalkeria'' * {{extinct}}''Caseosaurus'' * {{extinct}}''Chilesaurus'' * {{extinct}}''Chindesaurus'' * {{extinct}}''Daemonosaurus'' * {{extinct}}''Nyasasaurus'' * {{extinct}}'''Herrerasauridae''' {{Collapse bottom}} }} [[File:A special composite of birds.jpg|thumb|alt=montage of four birds|In the modern fauna, theropods are represented by over 11,000 species of birds, which are a group of maniraptoran theropods within the clade Avialae.]]

'''Theropoda''' ({{IPAc-en|θ|ɪ|'|r|ɒ|p|ə|d|ə}};<ref>{{cite Merriam-Webster|Theropoda}}</ref> from ancient Greek {{math|{{lang|grc|θηρίο-}}}} {{math|{{lang|grc|ποδός}}}} [<nowiki/>{{math|''θηρίον''}}, (''therion'') "wild beast"; {{math|''πούς''}}, {{math|''ποδός''}} (''pous, podos'') "foot"]) is one of the three major clades of dinosaur, alongside Ornithischia and Sauropodomorpha. Theropods, both extant and extinct, are characterized by hollow bones and three toes and claws on each limb. They are generally classed as a group of saurischian dinosaurs, placing them closer to sauropodomorphs than to ornithischians. They were ancestrally carnivorous, although a number of theropod groups evolved to become herbivores and omnivores. Members of the subgroup Coelurosauria were most likely all covered with feathers, and it is possible that they were also present in other theropods. In the Jurassic, birds evolved from small specialized coelurosaurian theropods, and are currently represented by about 11,000&nbsp;living species, making theropods the only group of dinosaurs alive today.

Theropods first appeared during the Carnian age of the Late Triassic period 231.4&nbsp;million years ago (Ma)<ref>{{cite journal |last1=Martinez |first1=Ricardo N. |last2=Sereno |first2=Paul C. |last3=Alcober |first3=Oscar A. |last4=Colombi |first4=Carina E. |last5=Renne |first5=Paul R. |last6=Montañez |first6=Isabel P. |last7=Currie |first7=Brian S. |title=A Basal Dinosaur from the Dawn of the Dinosaur Era in Southwestern Pangaea |journal=Science |date=14 January 2011 |volume=331 |issue=6014 |pages=206–210 |doi=10.1126/science.1198467 |pmid=21233386 |bibcode=2011Sci...331..206M |hdl=11336/69202 |hdl-access=free }}</ref> and included the majority of large terrestrial carnivores from the Early Jurassic until the end of the Cretaceous, about 66&nbsp;Ma, including the largest terrestrial carnivorous animals ever, such as ''Tyrannosaurus'' and ''Giganotosaurus'', though non-avian theropods exhibited considerable size diversity, with some non-avian theropods like scansoriopterygids being no bigger than small birds.

==Biology==

=== Traits === Various synapomorphies for Theropoda have been proposed based on which taxa are included in the group. For example, a 1999 paper by Paul Sereno suggests that theropods are characterized by traits such as an ectopterygoid fossa (a depression around the ectopterygoid bone), an intramandibular joint located within the lower jaw, and extreme internal cavitation within the bones.<ref>{{cite journal |last1=Sereno |first1=Paul C. |title=The Evolution of Dinosaurs |journal=Science |date=25 June 1999 |volume=284 |issue=5423 |pages=2137–2147 |doi=10.1126/science.284.5423.2137 |pmid=10381873 }}</ref> However, since taxa like ''Herrerasaurus'' may not be theropods, these traits may have been more widely distributed among early saurischians rather than being unique to theropods.

Instead, taxa with a higher probability of being within the Theropoda may share more specific traits, such as a prominent promaxillary fenestra, cervical vertebrae with pleurocoels in the anterior part of the centrum leading to a more pneumatic neck, five or more sacral vertebrae, enlargement of the carpal bone, and a distally concave portion of the tibia, among a few other traits found throughout the skeleton. Like the early sauropodomorphs, the second digit in a theropod's hand is enlarged. Theropods also have a very well developed ball and socket joint near their neck and head.<ref name=Novas-Agnolin-etal-2021>{{cite journal |last1=Novas |first1=Fernando E. |last2=Agnolin |first2=Federico L. |last3=Ezcurra |first3=Martín D. |last4=Temp Müller |first4=Rodrigo |last5=Martinelli |first5=Agustín G. |last6=Langer |first6=Max C. |title=Review of the fossil record of early dinosaurs from South America, and its phylogenetic implications |journal=Journal of South American Earth Sciences |date=October 2021 |volume=110 |article-number=103341 |doi=10.1016/j.jsames.2021.103341 |bibcode=2021JSAES.11003341N }}</ref><ref>{{cite book |last1=Dingus |first1=Lowell |last2=Rowe |first2=Timothy |year=1998 |title=The mistaken extinction: Dinosaur evolution and the origin of birds |publisher=W.H. Freeman |isbn=978-0-7167-2944-0 |location=New York}}</ref>

Most theropods belong to the clade Neotheropoda, characterized by the reduction of several foot bones, thus leaving three toed footprints on the ground when they walk (tridactyl feet). Digit V was reduced to a remnant early in theropod evolution and was gone by the late Triassic. Digit I is reduced and generally do not touch the ground, and greatly reduced in some lineages.<ref>{{cite journal |last=Harris |first=J.D. |year=1997 |title=Four-toed theropod footprints and a paleomagnetic age from the Whetstone Falls Member of the Harebell Formation (Upper Cretaceous: Maastrichtian), northwestern Wyoming |journal=Cretaceous Research |volume=18 |issue=1 |page=139 |doi=10.1006/cres.1996.0053 |quote=(''Saurexallopus lovei'') |via=Dixie State University, St.&nbsp;George, UT |url=https://cactus.utahtech.edu/jharris/Saurexallopus.pdf }}</ref> They also lack a digit V on their hands and have developed a furcula which is otherwise known as a wishbone.<ref name=Novas-Agnolin-etal-2021/> Early neotheropods like the coelophysoids have a noticeable kink in the upper jaw known as a subnarial gap. Averostrans are some of the most derived theropods and contain the Tetanurae and Ceratosauria. While some used to consider coelophysoids and ceratosaurs to be within the same group due to features such as a fused hip, later studies showed that it is more likely that these were features ancestral to neotheropods and were lost in basal tetanurans.<ref>{{Cite book |last1=Holtz |first1=Thomas R. |title=Dinosaurs: the most complete, up-to-date encyclopedia for dinosaur lovers of all ages |last2=Rey |first2=Luis V. |date=2007 |publisher=Random House |isbn=978-0-375-82419-7 |edition=1st |location=New York}}</ref> Averostrans and their close relatives are united via the complete loss of any digit V remnants, fewer teeth in the maxilla, the movement of the tooth row further down the maxilla and a lacrimal fenestra. Averostrans also share features in their hips and teeth.<ref>{{cite journal |last1=Smith |first1=Nathan D. |last2=Makovicky |first2=Peter J. |last3=Hammer |first3=William R. |last4=Currie |first4=Philip J. |title=Osteology of Cryolophosaurus ellioti (Dinosauria: Theropoda) from the Early Jurassic of Antarctica and implications for early theropod evolution |journal=Zoological Journal of the Linnean Society |date=October 2007 |volume=151 |issue=2 |pages=377–421 |doi=10.1111/j.1096-3642.2007.00325.x |url=http://publication.plazi.org/id/FF9DFFDFFF9CFFFFFFDFCD51C053FFA0 }}</ref>

===Diet and teeth === [[File:Jinfengopteryx elegans 2.JPG|thumb|Specimen of the troodontid ''Jinfengopteryx elegans'', with seeds preserved in the stomach region]] Theropods exhibit a wide range of diets, from insectivores to herbivores and carnivores. Strict carnivory has always been considered the ancestral diet for theropods as a group, and a wider variety of diets was historically considered a characteristic exclusive to the avian theropods (birds). However, discoveries in the late 20th and early 21st centuries showed that a variety of diets existed even in more basal lineages.<ref name="zannoetal2009">{{cite journal |last1=Zanno |first1=Lindsay E. |last2=Gillette |first2=David D. |last3=Albright |first3=L. Barry |last4=Titus |first4=Alan L. |date=25 August 2010 |title=A new North American therizinosaurid and the role of herbivory in 'predatory' dinosaur evolution |journal=Proceedings of the Royal Society B |volume=276 |pages= 3505–3511|doi=10.1098/rspb.2009.1029 |pmid= 19605396|issue=1672 |pmc=2817200}}</ref> All early finds of theropod fossils showed them to be primarily carnivorous. Fossilized specimens of early theropods known to scientists in the 19th and early 20th centuries all possessed sharp teeth with serrated edges for cutting flesh, and some specimens even showed direct evidence of predatory behavior. For example, a ''Compsognathus longipes'' fossil was found with a lizard in its stomach, and a ''Velociraptor mongoliensis'' specimen was found locked in combat with a ''Protoceratops andrewsi'' (a type of ornithischian dinosaur). This was likely caused by a sand dune blowing over the two animals mid combat, resulting in fossilization.

The first confirmed non-carnivorous fossil theropods found were the therizinosaurs, originally known as "segnosaurs". First thought to be prosauropods, these enigmatic dinosaurs were later proven to be highly specialized, herbivorous theropods. Therizinosaurs possessed large abdomens for processing plant food, and small heads with beaks and leaf-shaped teeth. Further study of maniraptoran theropods and their relationships showed that therizinosaurs were not the only early members of this group to abandon carnivory. Several other lineages of early maniraptorans show adaptations for an omnivorous diet, including seed-eating (some troodontids) and insect-eating (many avialans and alvarezsaurs). Oviraptorosaurs, ornithomimosaurs and advanced troodontids were likely omnivorous as well, and some theropods (such as ''Masiakasaurus knopfleri'' and the spinosaurids) appear to have specialized in catching fish.<ref name=LC08>{{cite journal |last1=Longrich |first1=Nicholas R. |last2=Currie |first2=Philip J. |date=February 2009 |title=''Albertonykus borealis'', a new alvarezsaur (Dinosauria: Theropoda) from the Early Maastrichtian of Alberta, Canada: Implications for the systematics and ecology of the Alvarezsauridae |journal=Cretaceous Research |volume=30 |issue=1 |pages= 239–252|doi=10.1016/j.cretres.2008.07.005|bibcode=2009CrRes..30..239L }}</ref><ref name="holtzetal1998">{{Cite journal | last1 = Holtz | first1 = T. R. Jr. | last2 = Brinkman | first2 = D. L. | last3 = Chandler | first3 = C. L. | year = 1998 | title = Dental morphometrics and a possibly omnivorous feeding habit for the theropod dinosaur ''Troodon'' | journal = GAIA | volume = 15 | pages = 159–166}}</ref>

Diet is largely deduced by the tooth morphology,<ref name="HendrickxMateus14" /> tooth marks on bones of the prey, and gut contents. Some theropods, such as ''Baryonyx'', ''Lourinhanosaurus'', ornithomimosaurs, and birds, are known to use gastroliths, or gizzard-stones.

The majority of theropod teeth are blade-like, with serration on the edges,<ref name=Hendrickxetal15>{{cite journal |last1=Hendrickx |first1=Christophe |last2=Mateus |first2=Octávio |last3=Araújo |first3=Ricardo |title=A proposed terminology of theropod teeth (Dinosauria, Saurischia) |journal=Journal of Vertebrate Paleontology |date=3 September 2015 |volume=35 |issue=5 |article-number=e982797 |doi=10.1080/02724634.2015.982797 |bibcode=2015JVPal..35E2797H |url=https://figshare.com/articles/journal_contribution/1568195 }}</ref> called ziphodont. Others are pachydont or folidont depending on the shape of the tooth or denticles.<ref name=Hendrickxetal15 /> The morphology of the teeth is distinct enough to tell the major families apart,<ref name=HendrickxMateus14>{{cite journal |last1=Hendrickx |first1=Christophe |last2=Mateus |first2=Octávio |title=Abelisauridae (Dinosauria: Theropoda) from the Late Jurassic of Portugal and dentition-based phylogeny as a contribution for the identification of isolated theropod teeth |journal=Zootaxa |date=30 January 2014 |volume=3759 |issue=1 |pages=1–74 |doi=10.11646/zootaxa.3759.1.1 |pmid=24869965 }}</ref> which indicate different diet strategies. An investigation in July 2015 discovered that what appeared to be "cracks" in their teeth were actually folds that helped to prevent tooth breakage by strengthening individual serrations as they attacked their prey.<ref>{{cite news|last1=Geggel|first1=Laura|title=One tough bite: T. rex's teeth had secret weapon|url=https://www.foxnews.com/science/one-tough-bite-t-rexs-teeth-had-secret-weapon/|access-date=1 August 2015|publisher=Fox News|date=28 July 2015}}</ref> The folds helped the teeth stay in place longer, especially as theropods evolved into larger sizes and had more force in their bite.<ref>{{Cite web|url = http://phenomena.nationalgeographic.com/2015/08/17/special-serrations-gave-carnivorous-dinosaurs-an-evolutionary-edge|archive-url = https://web.archive.org/web/20150818052557/http://phenomena.nationalgeographic.com/2015/08/17/special-serrations-gave-carnivorous-dinosaurs-an-evolutionary-edge/|archive-date = August 18, 2015|title = Special Serrations Gave Carnivorous Dinosaurs an Evolutionary Edge|date = 17 August 2015}}</ref><ref>{{cite journal |last1=Brink |first1=K. S. |last2=Reisz |first2=R. R. |last3=LeBlanc |first3=A. R. H. |last4=Chang |first4=R. S. |last5=Lee |first5=Y. C. |last6=Chiang |first6=C. C. |last7=Huang |first7=T. |last8=Evans |first8=D. C. |title=Developmental and evolutionary novelty in the serrated teeth of theropod dinosaurs |journal=Scientific Reports |date=28 July 2015 |volume=5 |issue=1 |article-number=12338 |doi=10.1038/srep12338 |pmid=26216577 |pmc=4648475 |bibcode=2015NatSR...512338B }}</ref>

===Integument (skin, scales and feathers)=== [[File:Anchiornis feathers.jpg|thumb|left|Fossil of an ''Anchiornis'', showing large preserved feather imprints]] Mesozoic theropods were also very diverse in terms of skin texture and covering. Feathers or feather-like structures (filaments) are attested in most lineages of coelurosaurs (see feathered dinosaur). However, outside the coelurosaurs, feathers may have been confined to the young, smaller species, or limited parts of the animal. Many larger theropods had skin covered in small, bumpy scales. In some species, these were interspersed with larger scales. This type of skin is best known in the ceratosaur ''Carnotaurus'', which has been preserved with extensive skin impressions.<ref>{{cite journal |last1=Hendrickx |first1=Christophe |last2=Bell |first2=Phil R. |title=The scaly skin of the abelisaurid Carnotaurus sastrei (Theropoda: Ceratosauria) from the Upper Cretaceous of Patagonia |journal=Cretaceous Research |date=December 2021 |volume=128 |article-number=104994 |doi=10.1016/j.cretres.2021.104994 |bibcode=2021CrRes.12804994H }}</ref> Osteoderms, scales with a bony core, are known from ''Ceratosaurus'', which was discovered with segments of osteoderms on top of its neck and tail, probably forming a continuous row in life.<ref>{{Cite journal |last=Gilmore |first=Charles W. |date=1920 |title=Osteology of the carnivorous Dinosauria in the United States National Museum, with special reference to the genera Antrodemus (Allosaurus) and Ceratosaurus |journal=Bulletin of the United States National Museum |issue=110 |pages=i–159 |doi=10.5479/si.03629236.110.i |hdl=10088/10107 }}</ref> In carnosaurs rectangular scutate scales are known from the top of the feet and the underside of the tail in ''Concavenator,'' and from the underside of the neck in ''Allosaurus''.<ref>{{cite journal |last1=Hendrickx |first1=Christophe |last2=Bell |first2=Phil R. |last3=Pittman |first3=Michael |last4=Milner |first4=Andrew R. C. |last5=Cuesta |first5=Elena |last6=O'Connor |first6=Jingmai |last7=Loewen |first7=Mark |last8=Currie |first8=Philip J. |last9=Mateus |first9=Octávio |last10=Kaye |first10=Thomas G. |last11=Delcourt |first11=Rafael |title=Morphology and distribution of scales, dermal ossifications, and other non-feather integumentary structures in non-avialan theropod dinosaurs |journal=Biological Reviews |date=June 2022 |volume=97 |issue=3 |pages=960–1004 |doi=10.1111/brv.12829 |pmid=34991180 }}</ref>

There is evidence of some lineages of theropods being ancestrally feathered but losing them in favor of scales in later members. In tyrannosauroids, the early members ''Dilong'' and ''Yutyrannus'' are preserved with evidence of feathers, while in the later tyrannosaurids, like ''Tyrannosaurus'', ''Tarbosaurus'', ''Albertosaurus'', ''Gorgosaurus,'' and ''Daspletosaurus,'' there is evidence of scales, though it is unknown if they lost all feathers entirely.<ref>{{Cite journal |last1=Bell |first1=Phil R. |last2=Campione |first2=Nicolás E. |last3=Persons |first3=W. Scott |last4=Currie |first4=Philip J. |last5=Larson |first5=Peter L. |last6=Tanke |first6=Darren H. |last7=Bakker |first7=Robert T. |date=2017-06-07 |title=Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution |journal=Biology Letters |volume=13 |issue=6 |article-number=20170092 |doi=10.1098/rsbl.2017.0092 |pmc=5493735 |pmid=28592520}}</ref>

The coelurosaur lineages most distant from birds had feathers that were relatively short and composed of simple, possibly branching filaments.<ref>{{cite journal |last1=Göhlich |first1=Ursula B. |last2=Chiappe |first2=Luis M. |title=A new carnivorous dinosaur from the Late Jurassic Solnhofen archipelago |journal=Nature |date=16 March 2006 |volume=440 |issue=7082 |pages=329–332 |doi=10.1038/nature04579 |pmid=16541071 |bibcode=2006Natur.440..329G }}</ref> Simple filaments are also seen in therizinosaurs, which also possessed large, stiffened "quill"-like feathers. More fully feathered theropods, such as dromaeosaurids, usually retain scales only on the feet. Some species may have mixed feathers elsewhere on the body as well. ''Scansoriopteryx'' preserved scales near the underside of the tail,<ref name="czerkas2002">{{cite book |last1= Czerkas |first1= S.A. |last2= Yuan |first2= C. |year=2002 |section=An arboreal maniraptoran from northeast China |pages = 63–95 |editor-last = Czerkas |editor-first = S.J. |title = Feathered Dinosaurs and the Origin of Flight |series = The Dinosaur Museum Journal |volume = 1 |publisher = The Dinosaur Museum |location = Blanding, UT |section-url =http://www.dinosaur-museum.org/featheredinosaurs/arboreal_maniraptoran.pdf }}</ref> and ''Juravenator'' may have been predominantly scaly with some simple filaments interspersed.<ref name="Goehlich2006">{{cite journal | last1 = Goehlich | first1 = U.B. | last2 = Tischlinger | first2 = H. | last3 = Chiappe | first3 = L.M. | year = 2006 | title = ''Juraventaor starki'' (Reptilia, Theropoda) ein nuer Raubdinosaurier aus dem Oberjura der Suedlichen Frankenalb (Sueddeutschland): Skelettanatomie und Wiechteilbefunde | journal = Archaeopteryx | volume = 24 | pages = 1–26}}</ref> On the other hand, some theropods were completely covered with feathers, such as the anchiornithid ''Anchiornis'', which even had feathers on the feet and toes.<ref name="XU">{{cite journal |last1=Xu |first1=Xing |last2=Zhao |first2=Qi |last3=Norell |first3=Mark |last4=Sullivan |first4=Corwin |last5=Hone |first5=David |last6=Erickson |first6=Gregory |last7=Wang |first7=XiaoLin |last8=Han |first8=FengLu |last9=Guo |first9=Yu |title=A new feathered maniraptoran dinosaur fossil that fills a morphological gap in avian origin |journal=Science Bulletin |date=February 2009 |volume=54 |issue=3 |pages=430–435 |doi=10.1007/s11434-009-0009-6 |bibcode=2009SciBu..54..430X |doi-access= }}</ref>

Based on a relationships between tooth size and skull length and also a comparison of the degree of wear of the teeth of non-avian theropods and modern lepidosaurs, it is concluded that theropods had lips that protected their teeth from the outside. Visually, the snouts of such theropods as ''Daspletosaurus'' had more similarities with lizards than crocodilians, which lack lips.<ref>{{cite journal |first1=Thomas M. |last1=Cullen |first2=Derek William |last2=Larson |first3=Mark P. |last3=Witton |first4=Diane |last4=Scott |first5=Tea |last5=Maho |first6=Kirstin S. |last6=Brink |first7=David C. |last7=Evans |first8=Robert |last8=Reisz |display-authors=6 |date=30 March 2023 |title=Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology |journal=Science |volume=379 |issue=6639|pages=1348–1352 |doi=10.1126/science.abo7877 |doi-access=free |pmid=36996202 |bibcode=2023Sci...379.1348C }}</ref>

===Size=== {{Main|Dinosaur size#Theropods|l1=Dinosaur size}} [[File:Longest theropods.svg|alt=Graph showing relative sizes of five types of dinosaur compared with small human figure, each represented by silhouettes in different colours|thumb|upright=2.0|Size comparison of selected giant theropod dinosaurs – the longest (left) is ''Spinosaurus aegyptiacus'', shortest (right) is ''Carcharodontosaurus saharicus''.]] [[File:Bee hummingbird (Mellisuga helenae) adult male in flight-cropped.jpg|thumb|An adult male bee hummingbird, the smallest known theropod and smallest living dinosaur]] ''Tyrannosaurus'' was for many decades the largest and best-known theropod to the general public. Since its discovery, however, a number of other, comparably-sized giant carnivorous dinosaurs have been described, including ''Spinosaurus'', ''Carcharodontosaurus'', and ''Giganotosaurus''.<ref name="TH07">{{cite journal |last1=Therrien |first1=F. |last2=Henderson |first2=D. M. |year=2007 |title=My theropod is bigger than yours...or not: estimating body size from skull length in theropods |journal=Journal of Vertebrate Paleontology |volume=27 |issue=1 |pages=108–115 |doi=10.1671/0272-4634(2007)27[108:MTIBTY]2.0.CO;2|s2cid=86025320 }}</ref> These large theropod dinosaurs are estimated to exceed ''Tyrannosaurus'' in length, especially in the case of ''Spinosaurus'', though more recent studies and reconstructions show that ''Tyrannosaurus'', although shorter, was more heavily built and thus still comparable to them in mass and overall size. The largest known ''Tyrannosaurus'' specimens such as Sue and Scotty are currently estimated to be the most massive individual theropod specimens known to science, though by only a narrow margin; a considerable bias in sample size resulting from the much greater number of adult specimens in ''Tyrannosaurus'' compared to all other theropods of similar mass, combined with the majority of individual adult giant theropods (even with ''Tyrannosaurus'') never having entered the fossil record, mean it is difficult to judge which, if any, of these theropods was the largest by mass in reality.<ref name="Mallon&Hone24">{{Cite journal |last1=Mallon |first1=Jordan C. |last2=Hone |first2=David W. E. |date=July 24, 2024 |title=Estimation of maximum body size in fossil species: A case study using ''Tyrannosaurus rex'' |journal=Ecology and Evolution |language=en |volume=14 |issue=7 |article-number=11658 |doi=10.1002/ece3.11658 |issn=2045-7758 |pmc=11267449 |pmid=39050661|bibcode=2024EcoEv..1411658M }}</ref> There is still no clear explanation for exactly why giant theropods grew to be so massive compared to any land predators that came before and after them.

The largest extant theropod is the common ostrich, up to 2.74&nbsp;m (9&nbsp;ft) tall and weighing between 90 and 130&nbsp;kg (200 – 290&nbsp;lb).<ref>{{cite web|url = http://www.awf.org/wildlife-conservation/ostrich|title = Ostrich|website = African Wildlife Foundation|access-date = 28 October 2020}}</ref> The smallest non-avian theropod known from adult specimens is the anchiornithid '' Anchiornis huxleyi'', at 110&nbsp;grams in weight and 34 centimeters (1&nbsp;ft) in length.<ref name="XU" /> When modern birds are included, the bee hummingbird (''Mellisuga helenae'') is smallest at 1.9 g and 5.5&nbsp;cm (2.2&nbsp;in) long.<ref name="brus">{{cite journal |last1=Brusatte |first1=Stephen L. |last2=O'Connor |first2=Jingmai K. |last3=Jarvis |first3=Erich D. |title=The Origin and Diversification of Birds |journal=Current Biology |date=October 2015 |volume=25 |issue=19 |pages=R888–R898 |doi=10.1016/j.cub.2015.08.003 |pmid=26439352 |doi-access=free |bibcode=2015CBio...25.R888B |hdl=10161/11144 |hdl-access=free }}</ref><ref name="nhm">{{cite web |last1=Hendry|first1=Lisa |title=Are birds the only surviving dinosaurs? |url=https://www.nhm.ac.uk/discover/why-are-birds-the-only-surviving-dinosaurs.html |publisher=The Trustees of The Natural History Museum, London |access-date=14 April 2023 |date=2023}}</ref>

Recent theories propose that theropod body size shrank continuously over a period of 50&nbsp;million years, from an average of {{convert|163|kg|lb}} down to {{convert|0.8|kg|lb}}, eventually evolving into over 11,000 species of modern birds. This was based on evidence that theropods were the only dinosaurs to get continuously smaller, and that their skeletons changed four times as fast as those of other dinosaur species.<ref name="AP-20140731" /><ref name="BBC-28563682" />

=== Growth rates === In order to estimate the growth rates of theropods, scientists need to calculate both age and body mass of a dinosaur. Both of these measures can only be calculated through fossilized bone and tissue, so regression analysis and extant animal growth rates as proxies are used to make predictions. Fossilized bones exhibit growth rings that appear as a result of growth or seasonal changes, which can be used to approximate age at the time of death.<ref>{{cite journal |last1=Padian |first1=Kevin |last2=de Ricqlès |first2=Armand J. |last3=Horner |first3=John R. |title=Dinosaurian growth rates and bird origins |journal=Nature |date=July 2001 |volume=412 |issue=6845 |pages=405–408 |doi=10.1038/35086500 |pmid=11473307 |bibcode=2001Natur.412..405P }}</ref> However, the amount of rings in a skeleton can vary from bone to bone, and old rings can also be lost at advanced age, so scientists need to properly control these two possibly confounding variables.

Body mass is harder to determine as bone mass only represents a small proportion of the total body mass of animals. One method is to measure the circumference of the femur, which in non-avian theropod dinosaurs has been shown to be a relatively proportional to quadrupedal mammals,<ref name=Andrsn-HallMrtn-etal-1985>{{cite journal |last1=Anderson |first1=J. F. |last2=Hall-Martin |first2=A. |last3=Russell |first3=D. A. |title=Long-bone circumference and weight in mammals, birds and dinosaurs |journal=Journal of Zoology |date=September 1985 |volume=207 |issue=1 |pages=53–61 |doi=10.1111/j.1469-7998.1985.tb04915.x }}</ref> and use this measurement as a function of body weight, as the proportions of long bones like the femur grow proportionately with body mass.<ref name=Andrsn-HallMrtn-etal-1985/> The method of using extant animal bone proportion to body mass ratios to make predictions about extinct animals is known as the extant-scaling (ES) approach.<ref name=Campione-Evans-2020/> A second method, known as the volumetric-density (VD) approach, uses full-scale models of skeletons to make inferences about potential mass. The ES approach is better for wide-range studies including many specimens and doesn't require as much of a complete skeleton as the VD approach, but the VD approach allows scientists to better answer more physiological questions about the animal, such as locomotion and center of gravity.<ref name=Campione-Evans-2020>{{cite journal |last1=Campione |first1=Nicolás E. |last2=Evans |first2=David C. |year=2020 |title=The accuracy and precision of body mass estimation in non-avian dinosaurs |journal=Biological Reviews |volume=95 |issue=6 |pages=1759–1797 |doi=10.1111/brv.12638 |doi-access= |pmid=32869488 }}</ref>

The current consensus is that non-avian theropods didn't exhibit a group wide growth rate, but instead had varied rates depending on their size. However, all non-avian theropods had faster growth rates than extant reptiles, even when modern reptiles are scaled up to the large size of some non-avian theropods. As body mass increases, the relative growth rate also increases. This trend may be due to the need to reach the size required for reproductive maturity.<ref>{{cite journal |last1=Lee |first1=Andrew H. |last2=Werning |first2=Sarah |title=Sexual maturity in growing dinosaurs does not fit reptilian growth models |journal=Proceedings of the National Academy of Sciences |date=15 January 2008 |volume=105 |issue=2 |pages=582–587 |doi=10.1073/pnas.0708903105 |doi-access=free |pmc=2206579 |pmid=18195356 |bibcode=2008PNAS..105..582L }}</ref> For example, one of the smallest known theropods was ''Microraptor zhaoianus,'' which had a body mass of 200&nbsp;grams, grew at a rate of approximately 0.33&nbsp;grams per day.<ref name=Erickson-Rogers-Yerby-2001/> A comparable reptile of the same size grows at half of this rate. The growth rates of medium-sized non-avian theropods (100–1000&nbsp;kg) approximated those of precocial birds, which are much slower than altricial birds. Large theropods (1500–3500&nbsp;kg) grew even faster, similar to rates displayed by eutherian mammals.<ref name=Erickson-Rogers-Yerby-2001>{{cite journal |last1=Erickson |first1=Gregory M. |last2=Rogers |first2=Kristina Curry |last3=Yerby |first3=Scott A. |title=Dinosaurian growth patterns and rapid avian growth rates |journal=Nature |date=26 July 2001 |volume=412 |issue=6845 |pages=429–433 |doi=10.1038/35086558 |pmid=11473315 |bibcode=2001Natur.412..429E }}{{Erratum|doi=10.1038/nature16488|pmid=26675731|http://retractionwatch.com/2016/03/01/high-profile-critic-slams-nature-letters-about-dinosaur-growth-following-corrections/ ''Retraction Watch''}}</ref> The largest non-avian theropods, like ''Tyrannosaurus rex'', had similar growth dynamics to the largest living land animal today, the African elephant, which is characterized by a rapid period of growth until maturity, subsequently followed by slowing growth in adulthood.<ref>{{cite journal |last1=Horner |first1=John R. |last2=Padian |first2=Kevin |title=Age and growth dynamics of Tyrannosaurus rex |journal=Proceedings of the Royal Society of London. Series B: Biological Sciences |date=22 September 2004 |volume=271 |issue=1551 |pages=1875–1880 |doi=10.1098/rspb.2004.2829 |pmc=1691809 |pmid=15347508}}</ref>

===Stance and gait=== [[File:Struthio camelus - Etosha 2014 (1).jpg|thumb|An ostrich walking on a road in Etosha National Park, Namibia]] As a hugely diverse group of animals, the posture adopted by theropods likely varied considerably between various lineages through time.<ref name=Hutchinson2006>{{cite journal | last=Hutchinson | first=J.R. | date=March–April 2006 | title=The evolution of locomotion in archosaurs | journal=Comptes Rendus Palevol | volume=5 | issue=3–4 | pages=519–530 | doi=10.1016/j.crpv.2005.09.002 | bibcode=2006CRPal...5..519H | url=http://doc.rero.ch/record/15518/files/PAL_E2922.pdf }}</ref> All known theropods are bipedal, with the forelimbs reduced in length and specialized for a wide variety of tasks (see below). In modern birds, the body is typically held in a somewhat upright position, with the upper leg (femur) held parallel to the spine and with the forward force of locomotion generated at the knee. Scientists are not certain how far back in the theropod family tree this type of posture and locomotion extends.<ref name=Hutchinson2006/>

Non-avian theropods were first recognized as bipedal during the 19th century, before their relationship to birds was widely accepted. During this period, theropods such as carnosaurs and tyrannosaurids were thought to have walked with vertical femurs and spines in an upright, nearly erect posture, using their long, muscular tails as additional support in a kangaroo-like tripodal stance.<ref name=Hutchinson2006/> Beginning in the 1970s, biomechanical studies of extinct giant theropods cast doubt on this interpretation. Studies of limb bone articulation and the relative absence of trackway evidence for tail dragging suggested that, when walking, the giant, long-tailed theropods would have adopted a more horizontal posture with the tail held parallel to the ground.<ref name=Hutchinson2006/><ref name=newman1970>{{cite journal |last=Newman |first=B.H. |year=1970 |title=Stance and gait in the flesh-eating ''Tyrannosaurus'' |journal=Biological Journal of the Linnean Society |volume=2 |issue=2 |pages=119–123 |doi=10.1111/j.1095-8312.1970.tb01707.x |url=http://publication.plazi.org/id/FFA0107EFFCFFFE3803CFFE12A45FFEC }}</ref> However, the orientation of the legs in these species while walking remains controversial. Some studies support a traditional vertically oriented femur, at least in the largest long-tailed theropods,<ref name="newman1970"/> while others suggest that the knee was normally strongly flexed in all theropods while walking, even giants like the tyrannosaurids.<ref name=padiangaits>{{cite book |first1=K. |last1=Padian |first2=P.E. |last2=Olsen |year=1989 |section=Ratite footprints and the stance and gait of Mesozoic theropods |pages=231–241 |editor1-first=D.D. |editor1-last=Gillette |editor2-first=M.G. |editor2-last=Lockley |title=Dinosaur Tracks and Traces |publisher=Cambridge University Press |place=Cambridge, UK }}</ref><ref name=paulgaits>{{cite journal | last1 = Paul | first1 = G.S. | year = 1998 | title = Limb design, function and running performance in ostrich-mimics and tyrannosaurs | journal = Gaia | volume = 15 | pages = 257–270}}</ref> It is likely that a wide range of body postures, stances, and gaits existed in the many extinct theropod groups.<ref name=Hutchinson2006/><ref name=locomotion>{{cite journal | last1 = Farlow | first1 = J. O. | last2 = Gatesy | first2 = S. M. | last3 = Holtz | first3 = T. R. Jr. | last4 = Hutchinson | first4 = J. R. | last5 = Robinson | first5 = J. M. | year = 2000 | title = Theropod locomotion | journal = Am. Zool. | volume = 40 | issue = 4| pages = 640–663 | doi=10.1093/icb/40.4.640| doi-access = free }}</ref>

===Nervous system and senses=== Although rare, complete casts of theropod endocrania are known from fossils. Theropod endocrania can also be reconstructed from preserved brain cases without damaging valuable specimens by using a computed tomography scan and 3D reconstruction software. These finds are of evolutionary significance because they help document the emergence of the neurology of modern birds from that of earlier reptiles. An increase in the proportion of the brain occupied by the cerebrum seems to have occurred with the advent of the Coelurosauria and "continued throughout the evolution of maniraptorans and early birds."<ref name="csaharicus-endo">"Abstract", in Chure (2001). Pg. 19.{{full citation needed|date=October 2020}}</ref>

Studies show that theropods had very sensitive snouts. It is suggested they might have been used for temperature detection, feeding behavior, and wave detection.<ref>{{cite journal |last1=Barker |first1=Chris Tijani |last2=Naish |first2=Darren |last3=Newham |first3=Elis |last4=Katsamenis |first4=Orestis L. |last5=Dyke |first5=Gareth |title=Complex neuroanatomy in the rostrum of the Isle of Wight theropod Neovenator salerii |journal=Scientific Reports |date=16 June 2017 |volume=7 |issue=1 |article-number=3749 |doi=10.1038/s41598-017-03671-3 |pmid=28623335 |pmc=5473926 |bibcode=2017NatSR...7.3749B }}</ref><ref>{{cite journal |last1=Kawabe |first1=Soichiro |last2=Hattori |first2=Soki |title=Complex neurovascular system in the dentary of Tyrannosaurus |journal=Historical Biology |date=3 July 2022 |volume=34 |issue=7 |pages=1137–1145 |doi=10.1080/08912963.2021.1965137 |bibcode=2022HBio...34.1137K }}</ref>

===Forelimb morphology=== [[File:Mummified precocial bird wings in mid-Cretaceous Burmese amber (2016) fig. 1.png |left|thumb|Mummified enantiornithean wing (of an unknown genus) from Cenomanian amber from Myanmar]] Shortened forelimbs in relation to hind legs were a common trait among theropods, most notably in the abelisaurids (such as ''Carnotaurus'') and the tyrannosaurids (such as ''Tyrannosaurus''). This trait was, however, not universal: spinosaurids had well developed forelimbs, as did many coelurosaurs. The relatively robust forelimbs of one genus, ''Xuanhanosaurus'', led Dong Zhiming to suggest that the animal might have been quadrupedal.<ref name=Dong1984>{{cite journal |last1=Dong |first1=Z. |author1-link=Dong Zhiming |year=1984 |title=A new theropod dinosaur from the Middle Jurassic of Sichuan Basin |journal=Vertebrata PalAsiatica |volume=22 |issue=3 |pages=213–218 }}</ref> However, this is no longer thought to be likely.<ref name="rauhut2003"/>

The hands are also very different among the different groups. The most common form among non-avian theropods is an appendage consisting of three fingers; the digits I, II and III (or possibly II, III and IV), with sharp claws. Some basal theropods, like most Ceratosaurians, had four digits, and also a reduced metacarpal V (e.g. ''Dilophosaurus''). The majority of tetanurans had three,{{efn| Some genera within Avetheropoda, however, had four digits, see {{cite web |title="Theropoda&nbsp;I" on ''Avetheropoda'' |date=14 July 2006 |series=Department of Geology |publisher=University of Maryland |url=http://www.geol.umd.edu/~tholtz/G104/10422ther.htm }} }}<ref>{{cite journal | last1=Barta | first1=D.E. | last2=Nesbitt | first2=S.J. | last3=Norell | first3=M.A. | year=2017 | title=The evolution of the manus of early theropod dinosaurs is characterized by high inter- and intraspecific variation | journal=Journal of Anatomy | volume=232 | issue=1 | pages=80–104 | doi=10.1111/joa.12719 | pmid=29114853 | pmc=5735062 }}</ref> but some had even fewer.<ref>{{cite news | title=The first single-fingered dinosaur | date=January 2011 | website=phys.org | url=https://phys.org/news/2011-01-single-fingered-dinosaur.html }}</ref>

The forelimbs' scope of use is also believed to have also been different among different families. The spinosaurids could have used their powerful forelimbs to hold fish. Some small maniraptorans such as scansoriopterygids are believed to have used their forelimbs to climb in trees.<ref name=czerkas2002/> The wings of modern birds are used primarily for flight, though they are adapted for other purposes in certain groups. For example, aquatic birds such as penguins use their wings as flippers.

===Forelimb movement=== [[File:Archaeo-deinony hands.svg|thumb|right|250px|Diagram of ''Deinonychus'' (left) and ''Archaeopteryx'' (right) forelimbs illustrating wing-like posture]] Contrary to the way theropods have often been reconstructed in art and the popular media, the range of motion of theropod forelimbs was severely limited, especially compared with the forelimb dexterity of humans and other primates.<ref name=carpenter2002>{{cite journal |last1=Carpenter |first1=Kenneth |title=Forelimb biomechanics of nonavian theropod dinosaurs in predation |journal=Senckenbergiana Lethaea |date=June 2002 |volume=82 |issue=1 |pages=59–75 |doi=10.1007/BF03043773 }}</ref> Most notably, theropods and other bipedal saurischian dinosaurs (including the bipedal prosauropods) could not pronate their hands—that is, they could not rotate the forearm so that the palms faced the ground or backwards towards the legs. In humans, pronation is achieved by motion of the radius relative to the ulna (the two bones of the forearm). In saurischian dinosaurs, however, the end of the radius near the elbow was actually locked into a groove of the ulna, preventing any movement. Movement at the wrist was also limited in many species, forcing the entire forearm and hand to move as a single unit with little flexibility.<ref name="senter2005">{{cite journal |last1=Senter |first1=Phil |last2=Robins |first2=James H. |title=Range of motion in the forelimb of the theropod dinosaur ''Acrocanthosaurus atokensis'', and implications for predatory behaviour |journal=Journal of Zoology |date=July 2005 |volume=266 |issue=3 |pages=307–318 |doi=10.1017/S0952836905006989 |doi-access=free }}</ref> In theropods and prosauropods, the only way for the palm to face the ground would have been by lateral splaying of the entire forelimb, as in a bird raising its wing.<ref name="carpenter2002"/>

In carnosaurs like ''Acrocanthosaurus'', the hand itself retained a relatively high degree of flexibility, with mobile fingers. This was also true of more basal theropods, such as herrerasaurs. Coelurosaurs showed a shift in the use of the forearm, with greater flexibility at the shoulder allowing the arm to be raised towards the horizontal plane, and to even greater degrees in flying birds. However, in coelurosaurs, such as ornithomimosaurs and especially dromaeosaurids, the hand itself had lost most flexibility, with highly inflexible fingers. Dromaeosaurids and other maniraptorans also showed increased mobility at the wrist not seen in other theropods, thanks to the presence of a specialized half-moon shaped wrist bone (the semi-lunate carpal) that allowed the whole hand to fold backward towards the forearm in the manner of modern birds.<ref name=senter2005/>

===Paleopathology=== {{Main|Theropod paleopathology}} In 2001, Ralph E. Molnar published a survey of pathologies in theropod dinosaur bone. He found pathological features in 21&nbsp;genera from 10&nbsp;families. Pathologies were found in theropods of all body size although they were less common in fossils of small theropods, although this may be an artifact of preservation. They are very widely represented throughout the different parts of theropod anatomy. The most common sites of preserved injury and disease in theropod dinosaurs are the ribs and tail vertebrae. Despite being abundant in ribs and vertebrae, injuries seem to be "absent... or very rare" on the bodies' primary weight supporting bones like the sacrum, femur, and tibia. The lack of preserved injuries in these bones suggests that they were selected by evolution for resistance to breakage. The least common sites of preserved injury are the cranium and forelimb, with injuries occurring in about equal frequency at each site. Most pathologies preserved in theropod fossils are the remains of injuries like fractures, pits, and punctures, often likely originating with bites. Some theropod paleopathologies seem to be evidence of infections, which tended to be confined only to small regions of the animal's body. Evidence for congenital malformities have also been found in theropod remains. Such discoveries can provide information useful for understanding the evolutionary history of the processes of biological development. Unusual fusions in cranial elements or asymmetries in the same are probably evidence that one is examining the fossils of an extremely old individual rather than a diseased one.<ref name=molnar-pathology>{{cite book |last=Molnar |first=R.E. |year=2001 |section=Theropod paleopathology: A literature survey |title=Mesozoic Vertebrate Life |editor1-last=Tanke |editor1-first=D.H. |editor2-last=Carpenter |editor2-first=K. |publisher=Indiana University Press |pages=337–363 }}</ref>

===Swimming=== The trackway of a swimming theropod, the first in China of the ichnogenus named ''Characichnos'', was discovered at the Feitianshan Formation in Sichuan.<ref name=swimming>{{cite journal | last1 = Xing | first1 = L.D. | last2 = Lockley | first2 = M.G. | last3 = Zhang | first3 = J.P. | display-authors = etal | year = 2013 | title = A new Early Cretaceous dinosaur track assemblage and the first definite non-avian theropod swim trackway from China | journal = Chin Sci Bull | volume = 58 | issue = 19 | pages = 2370–2378 | doi = 10.1007/s11434-013-5802-6 | doi-access = free | bibcode = 2013ChSBu..58.2370X }}</ref> These swim tracks support the hypothesis that theropods were adapted to swimming and capable of traversing moderately deep water. Dinosaur swim tracks are considered to be rare trace fossils, and are among a class of vertebrate swim tracks that also include those of pterosaurs and crocodylomorphs. The study described and analyzed four complete natural molds of theropod foot prints that are now stored at the Huaxia Dinosaur Tracks Research and Development Center (HDT). These dinosaur footprints were in fact claw marks, which suggest that this theropod was swimming near the surface of a river and just the tips of its toes and claws could touch the bottom. The tracks indicate a coordinated, left-right, left-right progression, which supports the proposition that theropods were well-coordinated swimmers.<ref name=swimming/>

==Evolutionary history== [[File:Herrerasaurusskeleton.jpg|thumb|left|alt=Full skeleton of an early carnivorous dinosaur, displayed in a glass case in a museum|Possible early forms ''Herrerasaurus'' (large) and ''Eoraptor'' (small)]] During the late Triassic, a number of primitive proto-theropod and theropod dinosaurs existed and evolved alongside each other.

The earliest and most primitive of the theropod dinosaurs were the carnivorous ''Eodromaeus'' and, possibly, the herrerasaurids of Argentina. The herrerasaurs existed during the early late Triassic (Late Carnian to Early Norian). They were found in North America and South America and possibly also India and Southern Africa. The herrerasaurs were characterised by a mosaic of primitive and advanced features. Some paleontologists have in the past considered the herrerasaurians to be members of Theropoda, while other theorized the group to be basal saurischians, and may even have evolved prior to the saurischian-ornithischian split. Cladistic analysis following the discovery of ''Tawa'', another Triassic dinosaur, suggests the herrerasaurs likely were early theropods.<ref name=Nesbittetal2009>{{Cite journal |last1=Nesbitt |first1=S.J. |last2=Smith |first2=N.D. |last3=Irmis |first3=R.B. |last4=Turner |first4=A.H. |last5=Downs |first5=A. |last6=Norell |first6=M.A. |name-list-style=amp |date=11 December 2009 |title=A complete skeleton of a Late Triassic saurischian and the early evolution of dinosaurs |journal=Science |volume=326 |issue=5959 |pages=1530–1533 |doi=10.1126/science.1180350 |pmid=20007898 |bibcode=2009Sci...326.1530N }}</ref>

The earliest and most primitive unambiguous theropods are the Coelophysoidea. The coelophysoids were a group of widely distributed, lightly built and potentially gregarious animals. They included small hunters like ''Coelophysis'' and ''Camposaurus''. These successful animals continued from the Late Carnian (early Late Triassic) through to the Toarcian (late Early Jurassic). Although in the early cladistic classifications they were included under the Ceratosauria and considered a side-branch of more advanced theropods,<ref name=Rowe-Gauthier-1990>{{cite book |last1=Rowe |first1=T. |last2=Gauthier |first2=J. |author2-link = Jacques Gauthier |year=1990 |section=Ceratosauria |pages=151–168 |editor1=Weishampel, D.B. |editor2=Dodson, P. |editor3=Osmólska, H. |name-list-style=amp |title=The Dinosauria |publisher=University of California Press |place=Berkeley, CA / Los Angeles, CA / Oxford, UK }}</ref> they may have been ancestral to all other theropods (which would make them a paraphyletic group).<ref name=mortimerdml2001>{{cite web |last=Mortimer |first=M. |date=4 July 2001 |title=Rauhut's Thesis |series=Dinosaur Mailing List Archives |website=dml.cmnh.org |url=http://dml.cmnh.org/2001Jul/msg00110.html }}</ref><ref name=carranoetal2002>{{cite journal |last1=Carrano |first1=Matthew T. |last2=Sampson |first2=Scott D. |last3=Forster |first3=Catherine A. |title=The osteology of ''Masiakasaurus knopfleri'', a small abelisauroid (Dinosauria: Theropoda) from the Late Cretaceous of Madagascar |journal=Journal of Vertebrate Paleontology |date=19 September 2002 |volume=22 |issue=3 |pages=510–534 |doi=10.1671/0272-4634(2002)022[0510:TOOMKA]2.0.CO;2 }}</ref>

'''Neotheropoda''' (meaning "new theropods") is a clade that includes coelophysoids and more advanced theropod dinosaurs, and is the only group of theropods that survived the Triassic–Jurassic extinction event. Neotheropoda was named by R.T.&nbsp;Bakker in 1986 as a group including the relatively derived theropod subgroups Ceratosauria and Tetanurae, and excluding coelophysoids.<ref>{{cite book |last=Bakker |first=R.T. |author-link=Robert T. Bakker |year=1986 |title=The Dinosaur Heresies |publisher=William Morrow |place=New York, NY |url=http://doc.rero.ch/record/232376/files/PAL_E1363.pdf |via=doc.rero.ch}}</ref> However, most later researchers have used it to denote a broader group. Neotheropoda was first defined as a clade by Paul Sereno in 1998 as ''Coelophysis'' plus modern birds, which includes almost all theropods except the most primitive species.<ref>{{cite journal |last=Sereno |first=P. |author-link=Paul Sereno |year=1998 |title=A rationale for phylogenetic definitions, with application to the higher-level taxonomy of Dinosauria |journal=Neues Jahrbuch für Geologie und Paläontologie |type=annual |department=Abhandlungen |volume=210 |pages=41–83 |doi=10.1127/njgpa/210/1998/41 }}</ref> Dilophosauridae was formerly considered a small clade within Neotheropoda, but was later considered to be paraphyletic. By the Early Jurassic, all non-averostran neotheropods had gone extinct.<ref>{{cite journal |last1=Marsh |first1=Adam D. |last2=Rowe |first2=Timothy B. |year=2020 |title=A comprehensive anatomical and phylogenetic evaluation of Dilophosaurus wetherilli (Dinosauria, Theropoda) with descriptions of new specimens from the Kayenta Formation of northern Arizona |journal=Journal of Paleontology |volume=94 |issue=S78 |pages=1–103 |doi=10.1017/jpa.2020.14 |doi-access=free |bibcode=2020JPal...94S...1M }}</ref>

'''Averostra''' (or "bird snouts") is a clade within Neotheropoda that includes most theropod dinosaurs, namely Ceratosauria and Tetanurae. It represents the only group of post-Early Jurassic theropods. One important diagnostic feature of Averostra is the absence of the fifth metacarpal. Other saurischians retained this bone, albeit in a significantly reduced form.<ref name=averost>{{cite journal |last1=Sasso |first1=Cristiano Dal |last2=Maganuco |first2=Simone |last3=Cau |first3=Andrea |date=19 December 2018 |title=The oldest ceratosaurian (Dinosauria: Theropoda), from the Lower Jurassic of Italy, sheds light on the evolution of the three-fingered hand of birds |journal=PeerJ |volume=6 |article-number=e5976 |doi=10.7717/peerj.5976 |doi-access=free |pmid=30588396 |pmc=6304160 }}</ref>

The somewhat more advanced ceratosaurs (including ''Ceratosaurus'' and ''Carnotaurus'') appeared during the Early Jurassic and continued through to the Late Jurassic in Laurasia. They competed alongside their more anatomically advanced tetanuran relatives and—in the form of the abelisaur lineage—lasted to the end of the Cretaceous in Gondwana.

The Tetanurae are more specialised again than the ceratosaurs. They are subdivided into the basal Megalosauroidea (alternately Spinosauroidea) and the more derived Avetheropoda. Megalosauridae were primarily Middle Jurassic to Early Cretaceous predators, and their spinosaurid relatives' remains are mostly from Early and Middle Cretaceous rocks. Avetheropoda, as their name indicates, were more closely related to birds and are again divided into the Allosauroidea (the diverse carcharodontosaurs) and the Coelurosauria (a very large and diverse dinosaur group including the birds).

Thus, during the late Jurassic, there were no fewer than four distinct lineages of theropods—ceratosaurs, megalosaurs, allosaurs, and coelurosaurs—preying on the abundance of small and large herbivorous dinosaurs. All four groups survived into the Cretaceous, and two of those—the ceratosaurs and coelurosaurs—survived to end of the period, where they were geographically separate, the ceratosaurs in Gondwana and Europe, and the coelurosaurs in Laurasia.

Of all the theropod groups, the coelurosaurs were by far the most diverse. Some coelurosaur groups that flourished during the Cretaceous were the tyrannosaurids (including ''Tyrannosaurus''), the dromaeosaurids (including ''Velociraptor'' and ''Deinonychus'', which are remarkably similar in form to one of the oldest known birds, ''Archaeopteryx''),<ref name=ostrom1969>{{cite journal | last1 = Ostrom | first1 = J.H. |author1-link=John Ostrom | year = 1969 | title = Osteology of ''Deinonychus antirrhopus'', an unusual theropod from the Lower Cretaceous of Montana | journal = Peabody Museum Natural History Bulletin | volume = 30 | pages = 1–165 }}</ref><ref name=paul1988>{{cite book |last=Paul |first=G.S. |year=1988 |title=Predatory Dinosaurs of the World |place=New York, NY |publisher=Simon and Schuster Co. |isbn=0-671-61946-2 }}</ref> the bird-like troodontids and oviraptorosaurs, the ornithomimosaurs (or "ostrich Dinosaurs"), the strange giant-clawed herbivorous therizinosaurs, and the avialans, which include modern birds and is the only dinosaur lineage to survive the Cretaceous–Paleogene extinction event.<ref>{{cite book |last1=Dingus |first1=L. |last2=Rowe |first2=T. |year=1998 |title=The Mistaken Extinction: Dinosaur evolution and the origin of birds |publisher=Freeman }}</ref> While the roots of these various groups are found in the Middle Jurassic, they only became abundant during the Early Cretaceous. A few palaeontologists, such as Gregory S. Paul, have suggested that some or all of these advanced theropods were actually descended from flying dinosaurs or proto-birds like ''Archaeopteryx'' that lost the ability to fly and returned to a terrestrial habitat.<ref name=paul2002>{{cite book |last=Paul |first=G.S. |year=2002 |title=Dinosaurs of the Air: The evolution and loss of flight in dinosaurs and birds |place=Baltimore, MD |publisher=Johns Hopkins University Press |isbn=0-8018-6763-0 }}</ref>

The evolution of birds from other theropod dinosaurs has also been reported, with some of the linking features being the furcula (wishbone), pneumatized bones, brooding of the eggs, and (in coelurosaurs, at least) feathers.<ref name="AP-20140731">{{cite news |last=Borenstein |first=Seth |title=Study traces dinosaur evolution into early birds |url=http://apnews.excite.com/article/20140731/us-sci-shrinking-dinosaurs-a5c053f221.html |date=July 31, 2014 |work=AP News |access-date=August 3, 2014 |archive-date=23 October 2018 |archive-url=https://web.archive.org/web/20181023110310/http://apnews.excite.com/article/20140731/us-sci-shrinking-dinosaurs-a5c053f221.html }}</ref><ref name=BBC-28563682>{{cite news |url=https://www.bbc.co.uk/nature/28563682 |title=Dinosaurs 'shrank' regularly to become birds |author=Zoe Gough |publisher=BBC |date=31 July 2014}}</ref><ref name=SCI-20140731>{{cite journal |author=Lee, MichaelS.Y. |author2=Cau, Andrea |author3=Naish, Darren |author4=Dyke, Gareth J. |title=Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds |date=August 2014 |journal=Science |volume=345 |number=6196 |pages=562–566 |doi=10.1126/science.1252243 |pmid=25082702 |bibcode=2014Sci...345..562L }}</ref>

==Classification== ===History of classification=== [[File:Othniel Charles Marsh - Brady-Handy.jpg|thumb|upright|Othniel Charles Marsh, who coined the name Theropoda. Photo c. 1870]] O. C. Marsh coined the name Theropoda (meaning "beast feet") in 1881.<ref name=marsh1881>{{cite journal | last1 = Marsh | first1 = O.C. | year = 1881 | title = Principal characters of American Jurassic dinosaurs. Part V | journal = The American Journal of Science and Arts | volume = 21 | issue = 125 | series = 3 | pages = 417–423| doi = 10.2475/ajs.s3-21.125.417 | bibcode = 1881AmJS...21..417M }}</ref> Marsh initially named Theropoda as a suborder to include the family Allosauridae, but later expanded its scope, reranking it as an order to include a wide array of "carnivorous" dinosaur families, including Megalosauridae, Compsognathidae, Ornithomimidae, Plateosauridae and Anchisauridae (now known to be herbivorous sauropodomorphs) and Hallopodidae (subsequently revealed as relatives of crocodilians). Due to the scope of Marsh's Order Theropoda, it came to replace a previous taxonomic group that Marsh's rival E. D. Cope had created in 1866 for the carnivorous dinosaurs: '''Goniopoda''' ("angled feet").<ref name=rauhut2003>{{cite book |last=Rauhut |first=O.W. |year=2003 |title=The Interrelationships and Evolution of Basal Theropod Dinosaurs |publisher=Blackwell Publishing |isbn=0-901702-79-X }}</ref>

By the early 20th century, some palaeontologists, such as Friedrich von Huene, no longer considered carnivorous dinosaurs to have formed a natural group. Huene abandoned the name "Theropoda", instead using Harry Seeley's Order Saurischia, which Huene divided into the suborders Coelurosauria and Pachypodosauria. Huene placed most of the small theropod groups into Coelurosauria, and the large theropods and prosauropods into Pachypodosauria, which he considered ancestral to the Sauropoda (prosauropods were still thought of as carnivorous at that time, owing to the incorrect association of rauisuchian skulls and teeth with prosauropod bodies, in animals such as ''Teratosaurus'').<ref name=rauhut2003/> Describing the first known dromaeosaurid (''Dromaeosaurus albertensis'') in 1922,<ref>{{cite journal | last1 = Matthew | first1 = W.D. | author1-link = W. D. Matthew | last2 = Brown | first2 = B. | author2-link = Barnum Brown | year = 1922 | title = The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta | journal = Bulletin of the American Museum of Natural History | volume = 46 | pages = 367–385 }}</ref> W. D. Matthew and Barnum Brown became the first paleontologists to exclude prosauropods from the carnivorous dinosaurs, and attempted to revive the name "Goniopoda" for that group, but other scientists did not accept either of these suggestions.<ref name=rauhut2003/> [[File:AllosaurusAMNH5753.jpg|thumb|left|''Allosaurus'' was one of the first dinosaurs classified as a theropod.]] In 1956, "Theropoda" came back into use—as a taxon containing the carnivorous dinosaurs and their descendants—when Alfred Romer reclassified the Order Saurischia into two suborders, Theropoda and Sauropoda. This basic division has survived into modern palaeontology, with the exception of, again, the Prosauropoda, which Romer included as an infraorder of theropods. Romer also maintained a division between Coelurosauria and Carnosauria (which he also ranked as infraorders). This dichotomy was upset by the discovery of ''Deinonychus'' and ''Deinocheirus'' in 1969, neither of which could be classified easily as "carnosaurs" or "coelurosaurs". In light of these and other discoveries, by the late 1970s Rinchen Barsbold had created a new series of theropod infraorders: Coelurosauria, Deinonychosauria, Oviraptorosauria, Carnosauria, Ornithomimosauria, and Deinocheirosauria.<ref name=rauhut2003/>

With the advent of cladistics and phylogenetic nomenclature in the 1980s, and their development in the 1990s and 2000s, a clearer picture of theropod relationships began to emerge. Jacques Gauthier named several major theropod groups in 1986, including the clade Tetanurae for one branch of a basic theropod split with another group, the Ceratosauria. As more information about the link between dinosaurs and birds came to light, the more bird-like theropods were grouped in the clade Maniraptora (also named by Gauthier in 1986<ref name=Rowe-Gauthier-1990/>). These new developments also came with a recognition among most scientists that birds arose directly from maniraptoran theropods and, on the abandonment of ranks in cladistic classification, with the re-evaluation of birds as a subset of theropod dinosaurs that survived the Mesozoic extinctions and lived into the present.<ref name=rauhut2003/>

===Major groups=== [[File:Ceratosaurus mounted.jpg|thumb|''Ceratosaurus'', a ceratosaurid]] [[File:Irritator challengeri mount 01.jpg|thumb|right|''Irritator'', a spinosaurid]] [[File:Mapusaurus skulls.jpg|thumb|''Mapusaurus'', a carcharodontosaurid]] [[File:MicroraptorGui-PaleozoologicalMuseumOfChina-May23-08.jpg|thumb|right|''Microraptor'', a dromaeosaurid]] [[File:House sparrows in CP (60060).jpg|thumb|right|The house sparrow, an avian, is the world's most widespread extant wild theropod.<ref name="anderson2006">Anderson, Ted R. (2006). Biology of the Ubiquitous House Sparrow: from Genes to Populations. Oxford: Oxford University Press. {{ISBN|0-19-530411-X}}.</ref>]] The following is a simplified classification of theropod groups based on their evolutionary relationships, and organized based on the list of Mesozoic dinosaur species provided by Holtz.<ref name="Holtz2008" /> A more detailed version can be found at dinosaur classification. The dagger (†) is used to signify groups with no living members. *†Coelophysoidea (small, early predatory theropods; includes ''Coelophysis'' and close relatives) *†Ceratosauria (often elaborately horned, the dominant southern carnivores of the Late Cretaceous; includes ''Ceratosaurus'', the abelisaurids, the noasaurids, and their relatives) *Tetanurae ("stiff tails"; includes most theropods) :*†Megalosauroidea (early group of large carnivores, including the megalosaurids and the semi-aquatic spinosaurids) :*†Allosauroidea (a highly successful group of large terrestrial carnivores, dominant worldwide during the Late Jurassic, Early Cretaceous and the start of the Late Cretaceous; includes ''Allosaurus'' and its relatives, like the carcharodontosaurids) :*†Megaraptora (A group of medium to large, long-armed and large-clawed predatory theropods of unknown affinities; the dominant carnivores of the southern hemisphere during the Late Cretaceous) :*Coelurosauria (feathered theropods, with a range of body sizes and niches) ::*†Compsognathidae (early coelurosaurs with reduced forelimbs) ::*†Tyrannosauroidea (The tyrannosaurids, the dominant northern carnivores for most of the Late Cretaceous, and close relatives; often had reduced forelimbs) ::*†Ornithomimosauria ("ostrich-mimics"; mostly toothless; omnivores to possible herbivores) ::*Maniraptora ("hand snatchers"; had long, slender arms and fingers) :::*†Alvarezsauroidea (small insectivores with reduced forelimbs each bearing one enlarged claw) :::*†Therizinosauria (bipedal herbivores with large hand claws and small heads) :::*†Scansoriopterygidae (small, arboreal maniraptors with long third fingers) :::*†Oviraptorosauria (mostly toothless; their diet and lifestyle are uncertain) :::*Paraves ("near-birds"; generally carnivorous or omnivorous, sickle-claws) ::::*†Anchiornithidae (small, winged protobirds) ::::*†Dromaeosauridae (small to medium-sized predatory theropods) ::::*†Troodontidae (small, gracile predatory or omnivorous theropods) ::::*Avialae (birds and extinct relatives) :::::*†Omnivoropterygidae (large, early short-tailed avialans) :::::*†Confuciusornithidae (small toothless birds) :::::*†Enantiornithes (primitive tree-dwelling, flying birds) :::::*Euornithes (advanced flying birds) ::::::*†Yanornithiformes (toothed Cretaceous Chinese birds) ::::::*†Hesperornithes (specialized aquatic diving birds) ::::::*'''Aves''' (modern, beaked birds and their extinct relatives)

===Relationships=== The following family tree illustrates a synthesis of the relationships of the major theropod groups based on various studies conducted in the 2010s.<ref name=theropodphylogeny2015>{{cite journal | last1 = Hendrickx | first1 = C. | last2 = Hartman | first2 = S.A. | last3 = Mateus | first3 = O. | year = 2015 | title = An overview of non-avian theropod discoveries and classification | journal = PalArch's Journal of Vertebrate Palaeontology | volume = 12 | issue = 1 | pages = 1–73 }}</ref> {{clade| style=font-size:90%;line-height:90% |label1='''Theropoda''' |1={{clade |1=†Herrerasauridae 90 px |2={{clade |1=†''Eoraptor'' |2={{clade |1=†''Eodromaeus'' |2={{clade |1=†''Daemonosaurus'' |2={{clade |1=†''Tawa'' 90 px |label2=Neotheropoda |2={{clade |1=†Coelophysoidea 90 px |2={{clade |1=†Dilophosauridae 90 px |label2=Averostra |2={{clade |1=†Ceratosauria 120px |label2=Tetanurae |2={{clade |1=†Megalosauroidea 150px |label2=Avetheropoda |2={{clade |1=†Allosauroidea 120px |label2=Coelurosauria |2={{clade |1=†Tyrannosauroidea 150 px |2={{clade |1=†Compsognathidae 70px |2=Maniraptoriformes 70 px }} }} }} }} }} }} }} }} }} }} }} }} }} Averostra was named by G.S.&nbsp;Paul in 2002 as an apomorphy-based clade defined as the group including the Dromaeosauridae and other Avepoda with (an ancestor with) a promaxillary fenestra (''fenestra promaxillaris'') which can also be referred to as a maxillary fenestra,<ref>{{cite web |last=Carr |first=Thomas |date=2013-10-22 |title=Osteology&nbsp;VIII: The antorbital cavity |website=Tyrannosauroidea central |url=https://tyrannosauroideacentral.blogspot.com/2013/10/osteology-viii-antorbital-cavity.html |access-date=2024-04-02 }}</ref> an extra opening in the front outer side of the maxilla, the bone that makes up the upper jaw.<ref>{{cite book |last = Paul |first= G.S. |author-link = Gregory S. Paul |year = 2002 |title = Dinosaurs of the Air |publisher = The Johns Hopkins University Press |isbn= 978-0-8018-6763-7 |place = Baltimore, MD / London, UK |url = https://books.google.com/books?id=OUwXzD3iihAC |via = Google books }}</ref> It was later redefined by Martin Ezcurra and Gilles Cuny in 2007 as a node-based clade containing ''Ceratosaurus nasicornis'', ''Allosaurus fragilis'', their last common ancestor and all its descendants.<ref>{{cite journal |last1=Ezcurra |first1=M.D. |last2=Cuny |first2=G. |year=2007 |title=The coelophysoid ''Lophostropheus airelensis'', gen. nov.: A review of the systematics of ''"Liliensternus" airelensis'' from the Triassic-Jurassic outcrops of Normandy (France) |journal=Journal of Vertebrate Paleontology |volume=27 |issue=1 |pages=73–86 |doi=10.1671/0272-4634(2007)27[73:TCLAGN]2.0.CO;2 |url=https://www.researchgate.net/publication/216007083 |via=researchgate.net }}</ref> Mickey Mortimer commented that Paul's original apomorphy-based definition may make Averostra a much broader clade than the ''Ceratosaurus''+''Allosaurus'' node, potentially including all of Avepoda or more.<ref>{{Cite web |last=Mortimer |first=Mickey |date=2010-11-15 |title=Averostra and Avepoda |website=The Theropod Database Blog |url=https://theropoddatabase.blogspot.com/2010/11/averostra-and-avepoda.html|access-date=2020-09-06 }}</ref>

A large study of early dinosaurs by Dr Matthew G. Baron, David Norman and Paul M. Barrett (2017) published in the journal ''Nature'' suggested that Theropoda is actually more closely related to Ornithischia, to which it formed the sister group within the clade Ornithoscelida. This new hypothesis also recovered Herrerasauridae as the sister group to Sauropodomorpha in the redefined Saurischia and suggested that the hypercarnivore morphologies that are observed in specimens of theropods and herrerasaurids were acquired convergently.<ref name=Ornithoscelida>{{cite journal |last1=Baron |first1=Matthew G. |last2=Norman |first2=David B. |last3=Barrett |first3=Paul M. |title=A new hypothesis of dinosaur relationships and early dinosaur evolution |journal=Nature |date=23 March 2017 |volume=543 |issue=7646 |pages=501–506 |doi=10.1038/nature21700 |pmid=28332513 |bibcode=2017Natur.543..501B }}</ref><ref>{{cite news |title=New study shakes the roots of the dinosaur family tree |date=22 March 2017 |website=cam.ac.uk |publisher=University of Cambridge |place=Cambridge, UK |url=https://www.cam.ac.uk/research/news/new-study-shakes-the-roots-of-the-dinosaur-family-tree}}</ref> However, this phylogeny remains controversial and additional work is being done to clarify these relationships.<ref name=NAT-2017>{{cite journal |last1=Langer |first1=Max C. |last2=Ezcurra |first2=Martín D. |last3=Rauhut |first3=Oliver W. M. |last4=Benton |first4=Michael J. |last5=Knoll |first5=Fabien |last6=McPhee |first6=Blair W. |last7=Novas |first7=Fernando E. |last8=Pol |first8=Diego |last9=Brusatte |first9=Stephen L. |title=Untangling the dinosaur family tree |journal=Nature |date=2 November 2017 |volume=551 |issue=7678 |pages=E1–E3 |doi=10.1038/nature24011 |pmid=29094688 |bibcode=2017Natur.551E...1L |hdl=1983/d088dae2-c7fa-4d41-9fa2-aeebbfcd2fa3 |hdl-access=free }}</ref>

==Footnotes== {{notelist}}

==See also== {{Portal|Dinosaurs|Birds|Amphibians|Reptiles}} * Feathered dinosaurs * Origin of birds * Other major clades of dinosaur ** Marginocephalia ** Ornithopoda ** Sauropodomorpha ** Thyreophora

==References== {{reflist|25em}}

==External links== *{{commons-inline}}

{{Avemetatarsalia|state=autocollapse}} {{Theropoda|N.|state=autocollapse}} {{Birds}} {{Taxonbar|from=Q188438}} {{Authority control}}

Category:Theropoda Category:Dinosaur clades