View source for Tyrannosauridae

{{Short description|Family of dinosaurs}}
{{Good article}}
{{Automatic taxobox
| name = Tyrannosaurids
| fossil_range = [[Late Cretaceous]], <br/>{{fossil range|earliest=Cenomanian|83|66|latest=66}}
{{small|(possible [[Cenomanian]] occurrence of ''[[Labocania]]'')}}
| image = Tyrannosauridae Diversity2.jpg
| image_caption = Montage of six tyrannosaurids, clockwise from top left: ''[[Tyrannosaurus]]'', ''[[Daspletosaurus]]'', ''[[Tarbosaurus]]'', ''[[Gorgosaurus]]'', ''[[Zhuchengtyrannus]]'', and ''[[Alioramus]]''
| image_upright = 1.2
| taxon = Tyrannosauridae
| authority = [[Henry Fairfield Osborn|Osborn]], 1906
| display_parents = 3
| type_genus = {{extinct}}''[[Tyrannosaurus]]''
| type_genus_authority = Osborn, 1905
| subdivision_ranks = Subgroups<ref name="Holtz2008">Holtz, Thomas R. Jr. (2012) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages,'' [http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf Winter 2011 Appendix.] {{Webarchive|url=https://web.archive.org/web/20170812011954/http://www.geol.umd.edu/~tholtz/dinoappendix/HoltzappendixWinter2011.pdf |date=2017-08-12 }}</ref>
| subdivision = * {{extinct}}''[[Aublysodon]]''
* {{extinct}}''[[Deinodon]]''
* {{extinct}}''[[Raptorex]]''
* {{extinct}}[[Albertosaurinae]]
* {{extinct}}[[Tyrannosaurinae]]
| synonyms = *Deinodontidae <small>[[Edward Drinker Cope|Cope]], 1866</small>
*Aublysodontidae <small>[[Franz Nopcsa von Felső-Szilvás|Nopcsa]], 1928</small>
*Shanshanosauridae <small>[[Dong Zhiming|Dong]], 1977</small>
}}
'''Tyrannosauridae''' (or '''tyrannosaurids''', meaning "[[tyrant]] lizards") is a [[family (biology)|family]] of [[coelurosauria]]n [[Theropoda|theropod]] [[dinosaur]]s that comprises two subfamilies containing up to fifteen [[genus|genera]], including the [[eponym]]ous ''[[Tyrannosaurus]]''. The exact number of genera is controversial, with some experts recognizing as few as three. All of these animals lived near the end of the [[Cretaceous]] [[Period (geology)|Period]] and their [[fossil]]s have been found only in [[North America]] and [[Asia]].

Although descended from [[Tyrannosauroidea|smaller ancestors]], tyrannosaurids were almost always the largest [[Predation|predators]] in their respective [[ecosystem]]s, putting them at the [[apex predator|apex]] of the [[food chain]]. The largest [[species]] was ''Tyrannosaurus rex'', the most massive known terrestrial predator, which measured over {{convert|13|m}} in length<ref>[http://www.osel.cz/10883-scotty-ten-nejvetsi-tyranosaurus-ze-vsech.html Article about Scotty on ''Osel.cz'' (in Czech)]</ref> and according to most modern estimates up to {{convert|8.87|MT|ST}} in weight.<ref name="Persons">{{Cite journal |last1=Persons |first1=S. W. |last2=Currie |first2=P. J. |last3=Erickson |first3=G. M. |title=An Older and Exceptionally Large Adult Specimen of ''Tyrannosaurus rex'' |journal=The Anatomical Record |volume=303 |issue=4 |pages=656–672 |doi=10.1002/ar.24118 |pmid=30897281 |issn=1932-8486|year=2019 |doi-access=free }}</ref><ref name="Lyle2019">{{Cite web |url=https://www.folio.ca/paleontologists-identify-biggest-tyrannosaurus-rex-ever-discovered/ |title=Paleontologists identify biggest ''Tyrannosaurus rex'' ever discovered |last=Lyle |first=A. |date=March 22, 2019 |publisher=Folio, University of Alberta |access-date=March 25, 2019 |archive-date=August 4, 2020 |archive-url=https://web.archive.org/web/20200804134550/https://www.folio.ca/paleontologists-identify-biggest-tyrannosaurus-rex-ever-discovered/ |url-status=live }}</ref> Tyrannosaurids were [[Bipedalism|bipedal]] carnivores with massive [[skull]]s filled with large teeth. Despite their large size, their legs were long and proportioned for fast movement. In contrast, their arms were very small, bearing only two functional [[Digit (anatomy)|digits]].

Unlike most other groups of dinosaurs, very complete remains have been discovered for most known tyrannosaurids. This has allowed a variety of research into their [[biology]]. Scientific studies have focused on their [[ontogeny]], [[biomechanics]] and [[ecology]], among other subjects.

==History of discovery==
[[Image:Deinodon.JPG|thumb|left|''Deinodon'' teeth, the earliest known tyrannosaurid remains]]
The first remains of tyrannosaurids were uncovered during expeditions led by the [[Geological Survey of Canada]], which located numerous scattered teeth. These distinctive dinosaur teeth were given the name ''[[Deinodon]]'' ("terrible tooth") by [[Joseph Leidy]] in 1856. The first good specimens of a tyrannosaurid were found in the [[Horseshoe Canyon Formation]] of [[Alberta]], and consisted of nearly complete skulls with partial skeletons. These remains were first studied by [[Edward Drinker Cope]] in 1876, who considered them a species of the eastern tyrannosauroid ''[[Dryptosaurus]]''. In 1905, [[Henry Fairfield Osborn]] recognized that the Alberta remains differed considerably from ''Dryptosaurus'', and coined a new name for them: ''[[Albertosaurus|Albertosaurus sarcophagus]]'' ("flesh-eating Alberta lizard").<ref name=carpenter1992/> Cope described more tyrannosaur material in 1892, in the form of isolated vertebrae, and gave this animal the name ''[[Manospondylus|Manospondylus gigas]]''. This discovery was mostly overlooked for over a century, and caused controversy in the early 2000s when it was discovered that this material actually belonged to, and had name priority over, ''[[Tyrannosaurus|Tyrannosaurus rex]]''.<ref name=quinlanetal2007b>{{cite conference |first1=B.H. |last1=Breithaupt |last2=Southwell |first2=E.H. |last3=Matthews |first3=N.A. |date=18 October 2005 |title=In Celebration of 100 years of ''Tyrannosaurus rex'': ''Manospondylus gigas'', ''Ornithomimus grandis'', and ''Dynamosaurus imperiosus'', the Earliest Discoveries of ''Tyrannosaurus rex'' in the West |conference=2005 Salt Lake City Annual Meeting |conference-url=http://gsa.confex.com/gsa/2005AM/finalprogram/index.html |book-title=Abstracts with Programs |volume=37 |issue=7 |publisher=[[Geological Society of America]] |page=406 |url=http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96150.htm |access-date=8 October 2008 |archive-date=22 October 2019 |archive-url=https://web.archive.org/web/20191022084528/https://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96150.htm |url-status=live }}</ref>
[[Image:Aublysodon.jpg|thumb|Teeth that have been assigned to ''Aublysodon'' at various times]]
In his 1905 paper naming ''Albertosaurus'', Osborn described two additional tyrannosaur specimens that had been collected in [[Montana]] and [[Wyoming]] during a 1902 expedition of the [[American Museum of Natural History]], led by [[Barnum Brown]]. Initially, Osborn considered these to be distinct species. The first, he named ''Dynamosaurus imperiosus'' ("emperor power lizard"), and the second, ''Tyrannosaurus rex'' ("king tyrant lizard"). A year later, Osborn recognized that these two specimens actually came from the same species. Despite the fact that ''Dynamosaurus'' had been found first, the name ''Tyrannosaurus'' had appeared one page earlier in his original article describing both specimens. Therefore, according to the [[International Code of Zoological Nomenclature]] (ICZN), the name ''Tyrannosaurus'' was used.<ref name="Breithaup">{{Cite journal|last=Breithaup|first=BH|author2=Southwell EH |author3=Matthews NA |year=2006|title=''Dynamosaurus imperiosus'' and the earliest discoveries of ''Tyrannosaurus rex'' in Wyoming and the West|journal=New Mexico Museum of Natural History and Science Bulletin |volume=35 |pages=257–258}}</ref>

Barnum Brown went on to collect several more tyrannosaurid specimens from Alberta, including the first to preserve the shortened, two-fingered forelimbs characteristic of the group (which [[Lawrence Lambe]] named ''[[Gorgosaurus|Gorgosaurus libratus]]'', "balanced fierce lizard", in 1914). A second significant find attributed to ''Gorgosaurus'' was made in 1942, in the form of a well-preserved, though unusually small, complete skull. The specimen waited until after the end of [[World War II]] to be studied by [[Charles W. Gilmore]], who named it ''Gorgosaurus lancesnis''.<ref name=carpenter1992/> This skull was re-studied by [[Robert T. Bakker]], [[Philip J. Currie|Phil Currie]], and Michael Williams in 1988, and assigned to the new genus ''[[Nanotyrannus]]''.<ref name="bakkeretal1988">{{cite journal |author1=Bakker R.T |author2=Williams M. |author3=Currie P. | year = 1988 | title = ''Nanotyrannus'', a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana | journal = Hunteria | volume = 1 | pages = 1–30 }}</ref> It was also in 1946 that paleontologists from the [[Soviet Union]] began expeditions into [[Mongolia]], and uncovered the first tyrannosaur remains from Asia. [[Evgeny Maleev]] described new Mongolian species of ''Tyrannosaurus'' and ''Gorgosaurus'' in 1955, and one new genus: ''[[Tarbosaurus]]'' ("terrifying lizard"). Subsequent studies, however, showed that all of Maleev's tyrannosaur species were actually one species of ''Tarbosaurus'' at different stages of growth. A second species of Mongolian tyrannosaurid was found later, described by Sergei Kurzanov in 1976, and given the name ''[[Alioramus|Alioramus remotus]]'' ("remote different branch"), though its status as a true tyrannosaurid and not a more primitive tyrannosaur is still controversial.<ref name="kurzanov1976"/><ref name=carpenter1992/>

==Description==
[[File:Tyrannosauridae Size Diagram by PaleoGeek.svg|thumb|left|Size comparison of large tyrannosaurid genera ''[[Tyrannosaurus]]'', ''[[Tarbosaurus]]'', ''[[Albertosaurus]]'', ''[[Gorgosaurus]]'' and ''[[Daspletosaurus]]'']]
The tyrannosaurids were all large animals, with all species capable of weighing at least 1 metric ton.<ref name=holtz2004>{{Cite book|last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |year=2004 |chapter=Tyrannosauroidea |editor= [[David B. Weishampel|Weishampel, David B.]] |editor2=[[Peter Dodson|Dodson, Peter]] |editor3=Osmólska, Halszka |title=The Dinosauria |edition=Second |publisher=University of California Press |location=Berkeley |pages=111–136 |isbn=978-0-520-24209-8}}</ref> A single specimen of ''[[Alioramus]]'' of an individual estimated at between {{convert|5|and|6|m}} long has been discovered,<ref name=kurzanov1976>{{Cite journal|last=Kurzanov |first=Sergei M. |author-link=Sergei Kurzanov |title=A new carnosaur from the Late Cretaceous of Nogon-Tsav, Mongolia |language=ru |journal=The Joint Soviet-Mongolian Paleontological Expedition Transactions |volume=3 |pages=93–104}}</ref> although it is considered by some experts to be a juvenile.<ref name=holtz2004/><ref name=currie2003a>{{Cite journal |last=Currie |first=Philip J. |author-link=Phil Currie |year=2003 |title=Cranial anatomy of tyrannosaurids from the Late Cretaceous of Alberta |journal=Acta Palaeontologica Polonica |volume=48 |issue=2 |pages=191–226 |url=http://www.app.pan.pl/archive/published/app48/app48-191.pdf |access-date=2010-06-12 |archive-date=2018-08-19 |archive-url=https://web.archive.org/web/20180819050324/http://www.app.pan.pl/archive/published/app48/app48-191.pdf |url-status=live }}</ref> ''[[Albertosaurus]]'', ''[[Gorgosaurus]]'' and ''[[Daspletosaurus]]'' all measured between {{convert|8|and|9|m}} long,<ref name=russell1970>{{Cite journal|last=Russell |first=Dale A. |author-link=Dale Russell |year=1970 |title=Tyrannosaurs from the Late Cretaceous of western Canada |journal=National Museum of Natural Sciences Publications in Paleontology |volume=1 |pages=1–34}}</ref> while ''[[Tarbosaurus]]'' reached lengths of {{convert|11|m}} from snout to tail.<ref name=MMDML03>{{cite web|publisher=The Dinosaur Mailing List |url=http://dml.cmnh.org/2003Jul/msg00355.html |title=And the largest Theropod is... |last=Mortimer |first=Mickey |date=21 July 2003 |access-date=8 September 2007 |archive-url=https://web.archive.org/web/20100325195202/http://dml.cmnh.org/2003Jul/msg00355.html |archive-date=25 March 2010 |url-status=live}}</ref> The massive ''[[Tyrannosaurus]]'' reached {{convert|13|m}} in the largest specimen, [[Scotty (dinosaur)|RSM P2523.8]].<ref>[http://www.osel.cz/10883-scotty-ten-nejvetsi-tyranosaurus-ze-vsech.html Article about Scotty on ''Osel.cz'' (in Czech)]</ref>

===Skull and dentition===
{{multiple image
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 | image1 = Lythronax.png
 | caption1 = Labelled ''[[Lythronax]]'' skull

 | image2 = Nanuqsaurus hoglundi.png
 | caption2 = Labelled ''[[Nanuqsaurus]]'' skull

 | image3 = Skull and jaws of the holotype (MOR 590) of Daspletosaurus horneri.jpg
 | caption3 = Labelled ''[[Daspletosaurus]]'' skull

 | image4 = Teratophoneus.png
 | caption4 = Labelled ''[[Teratophoneus]]'' skull
}}
Tyrannosaurid skull anatomy is well understood, as complete skulls are known for all genera but ''Alioramus'', which is known only from partial skull remains.<ref>{{Cite book|last=Currie |first=Philip J. |author-link=Phil Currie |year=2000 |chapter=Theropods from the Cretaceous of Mongolia |title=The Age of Dinosaurs in Russia and Mongolia |location=Cambridge |publisher=Cambridge University Press |pages=434–455 |isbn=978-0-521-54582-2}}</ref> ''Tyrannosaurus'', ''Tarbosaurus'', and ''Daspletosaurus'' had skulls that exceeded {{convert|1|m|ft|abbr=on}} in length.<ref name="russell1970"/> Adult tyrannosaurids had tall, massive skulls, with many bones fused and reinforced for strength. At the same time, hollow chambers within many skull bones and large openings ([[fenestra]]e) between those bones helped to reduce skull weight. Many features of tyrannosaurid skulls were also found in their immediate ancestors, including tall [[premaxilla]]e and fused [[nasal bone]]s.<ref name=holtz2004/>

Tyrannosaurid skulls had many unique characteristics, including fused [[parietal bone]]s with a prominent [[sagittal crest]], which ran [[Anatomical plane|longitudinally]] along the [[sagittal suture]] and separated the two supratemporal fenestrae on the skull roof. Behind these fenestrae, tyrannosaurids had a characteristically tall nuchal crest, which also arose from the parietals but ran along a [[transverse plane]] rather than longitudinally. The nuchal crest was especially well-developed in ''Tyrannosaurus'', ''Tarbosaurus'' and ''Alioramus''. ''Albertosaurus'', ''Daspletosaurus'' and ''Gorgosaurus'' had tall crests in front of the eyes on the [[lacrimal bone]]s, while ''Tarbosaurus'' and ''Tyrannosaurus'' had extremely thickened [[postorbital]] bones forming crescent-shaped crests behind the eyes. ''Alioramus'' had a row of six bony crests on top of its snout, arising from the nasal bones; lower crests have been reported on some specimens of ''Daspletosaurus'' and ''Tarbosaurus'', as well as the more [[basal (phylogenetics)|basal]] tyrannosauroid ''[[Appalachiosaurus]]''.<ref name=currie2003a/><ref name=carretal2005>{{Cite journal|last=Carr |first=Thomas D. |author2=Williamson, Thomas E. |author3= Schwimmer, David R. |year=2005 |title=A new genus and species of tyrannosauroid from the Late Cretaceous (middle Campanian) Demopolis Formation of Alabama |journal=Journal of Vertebrate Paleontology |volume=25 |issue=1 |pages=119–143 |doi=10.1671/0272-4634(2005)025[0119:ANGASO]2.0.CO;2|s2cid=86243316 |issn=0272-4634}}</ref> The snout and other parts of the skull also sported numerous [[Foramen|foramina]]. According to the 2017 study which described ''[[Daspletosaurus horneri|D. horneri]]'', scaly integument as well as tactile sensitivity was correlated with the multiple rows of neurovascular foramina seen in [[crocodilians]] and tyrannosaurids.<ref>{{Cite journal|last1=Carr|first1=Thomas D.|last2=Varricchio|first2=David J.|last3=Sedlmayr|first3=Jayc C.|last4=Roberts|first4=Eric M.|last5=Moore|first5=Jason R.|date=2017-03-30|title=A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system|journal=Scientific Reports|language=en|volume=7|issue=1|article-number=44942|doi=10.1038/srep44942|issn=2045-2322|pmid=28358353|bibcode=2017NatSR...744942C|pmc=5372470}}</ref>
{{multiple image
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 | image1 = B-rex teeth.jpg
 | image2 = The Childrens Museum of Indianapolis - Tyrannosaurus rex tooth.jpg
 | footer = ''Tyrannosaurus'' teeth
}}
Tyrannosaurids, like their tyrannosauroid ancestors, were [[heterodont]]s, with premaxillary teeth ''D''-shaped in [[Cross section (geometry)|cross section]] and smaller than the rest. Unlike earlier tyrannosauroids and most other theropods, the [[maxilla]]ry and [[mandible|mandibular]] teeth of mature tyrannosaurids are not blade-like but extremely thickened and often circular in cross-section, with some species having reduced serrations.<ref name=holtz2004/> Tooth counts tend to be consistent within species, and larger species tend to have lower tooth counts than smaller ones. For example, ''Alioramus'' had 76 to 78 teeth in its jaws, while ''Tyrannosaurus'' had between 54 and 60.<ref name=currieetal2003>{{Cite journal |last=Currie |first=Philip J. |author2=Hurum, Jørn H |author3=Sabath, Karol. |author-link=Phil Currie |year=2003 |title=Skull structure and evolution in tyrannosaurid phylogeny |journal=Acta Palaeontologica Polonica |volume=48 |issue=2 |pages=227–234 |url=http://www.app.pan.pl/archive/published/app48/app48-227.pdf |access-date=2010-10-02 |archive-date=2008-10-31 |archive-url=https://web.archive.org/web/20081031093118/http://www.app.pan.pl/archive/published/app48/app48-227.pdf |url-status=live }}</ref>

[[William Abler]] observed in 2001 that ''Albertosaurus'' [[tooth serrations]] resemble a [[Fracture|crack]] in the tooth ending in a round void called an ampulla.<ref name="abler-2001">Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p.&nbsp;84–89. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.</ref> [[Tyrannosaurus|Tyrannosaurid]] teeth were used as holdfasts for pulling [[meat]] off a body, so when a tyrannosaur would have pulled back on a piece of meat, the tension could cause a purely crack-like serration to spread through the tooth.<ref name="abler-2001" /> However, the presence of the ampulla would have distributed these forces over a larger [[surface area]], and lessened the risk of damage to the tooth under strain.<ref name="abler-2001" /> The presence of incisions ending in voids has parallels in human engineering. [[Guitar]] makers use incisions ending in voids to, as Abler describes, "impart alternating regions of flexibility and rigidity" to the wood they work with.<ref name="abler-2001" /> The use of a [[drill]] to create an "ampulla" of sorts and prevent the propagation of cracks through material is also used to protect [[airplane]] surfaces.<ref name="abler-2001" /> Abler demonstrated that a plexiglass bar with incisions called "kerfs" and drilled holes was more than 25% stronger than one with only regularly placed incisions.<ref name="abler-2001" /> Unlike tyrannosaurs and other theropods, ancient predators like [[phytosaur]]s and ''[[Dimetrodon]]'' had no adaptations to prevent the crack-like serrations of their teeth from spreading when subjected to the forces of feeding.<ref name="abler-2001" />

===Postcranial skeleton===
[[File:Journal.pone.0079420.g001.tif|thumb|Skeletal diagrams of ''Lythronax'' and ''Teratophoneus'']]
The skull was perched at the end of a thick, ''S''-shaped neck, and a long, heavy tail acted as a [[counterweight]] to balance out the head and torso, with the [[center of mass]] over the hips. Tyrannosaurids are known for their proportionately very small two-fingered forelimbs, although remnants of a [[Vestigiality|vestigial]] third digit are sometimes found.<ref name=holtz2004/><ref name=quinlanetal2007a>{{Cite journal |last=Quinlan |first=Elizabeth D. |author2=Derstler, Kraig |author3=Miller, Mercedes M. |year=2007 |title=Anatomy and function of digit III of the ''Tyrannosaurus rex'' manus |journal=Geological Society of America Annual Meeting&nbsp;— Abstracts with Programs |page=77 |url=http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm |access-date=2008-01-15 |archive-date=2008-02-24 |archive-url=https://web.archive.org/web/20080224015023/http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm |url-status=live }} [abstract only]</ref> ''Tarbosaurus'' had the shortest forelimbs compared to its body size, while ''Daspletosaurus'' had the longest.
[[File:Gorgosaurus forelimb.png|thumb|150px|left|Labelled diagram of the right arm and shoulder blade of ''[[Gorgosaurus]]'']]
Tyrannosaurids walked exclusively on their hindlimbs, so their leg bones were massive. In contrast to the forelimbs, the hindlimbs were longer compared to body size than almost any other theropods. Juveniles and even some smaller adults, like more basal tyrannosauroids, had longer [[tibia]]e than [[femur|femora]], a characteristic of [[cursorial]] (fast-running) dinosaurs like [[Ornithomimosauria|ornithomimids]]. Larger adults had leg proportions characteristic of slower-moving animals, but not to the extent seen in other large theropods like [[Abelisauridae|abelisaurids]] or [[Carnosauria|carnosaurs]]. The third [[Metatarsal bones|metatarsals]] of tyrannosaurids were pinched between the second and fourth metatarsals, forming a structure known as the [[Arctometatarsal|arctometatarsus]].<ref name=holtz2004/> Tyrannosaurids also had large preserved leg muscle attachments and low rotational [[inertia]] relative to their body mass, indicating that they could turn more quickly than other large theropods.<ref>{{Cite journal |last1=Snively |first1=Eric |last2=O'Brien |first2=Haley |last3=Henderson |first3=Donald M. |last4=Mallison |first4=Heinrich |last5=Surring |first5=Lara A. |last6=Burns |first6=Michael E. |last7=Holtz |first7=Thomas R. |last8=Russell |first8=Anthony P. |last9=Witmer |first9=Lawrence M. |last10=Currie |first10=Philip J. |last11=Hartman |first11=Scott A. |last12=Cotton |first12=John R. |date=2019-02-21 |title=Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods |journal=PeerJ |volume=7 |article-number=e6432 |doi=10.7717/peerj.6432 |doi-access=free |issn=2167-8359 |pmc=6387760 |pmid=30809441}}</ref><ref>{{Cite web |last=Hartman |first=Scott |date=2019-02-21 |title=Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods |url=https://www.scotthartman.info/publication/snively-2019-lower/ |access-date=2023-12-29 |website=Scott Hartman - PhD |language=en-us}}</ref>

It is unclear when the arctometatarsus first evolved; it was not present in the earliest tyrannosauroids like ''[[Dilong paradoxus|Dilong]]'',<ref name=xuetal2004>{{Cite journal|last1= Xu Xing |author2=Norell, Mark A. |author3=Kuang Xuewen |author4=Wang Xiaolin |author5=Zhao Qi |author6= Jia Chengkai. |year=2004 |title=Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids |journal=Nature |volume=431 |issue=7009 |pages=680–684 |doi=10.1038/nature02855 |pmid= 15470426 |first1= X|bibcode=2004Natur.431..680X |s2cid=4381777 |url=http://doc.rero.ch/record/15283/files/PAL_E2582.pdf |author1-link=Xu Xing (paleontologist) }}</ref> but was found in the later ''[[Appalachiosaurus]]''.<ref name=carretal2005/> This structure also characterized [[Troodontidae|troodontids]], [[Ornithomimosauria|ornithomimids]] and [[Caenagnathidae|caenagnathids]],<ref name=holtz1994>{{Cite journal|last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |year=1994 |title=The phylogenetic position of the Tyrannosauridae: implications for theropod systematics |journal=Journal of Paleontology |volume=68 |issue=5 |pages=1100–1117 |jstor=1306180|doi=10.1017/S0022336000026706 |bibcode=1994JPal...68.1100H |s2cid=129684676 }}</ref> but its absence in the earliest tyrannosauroids indicates that it was acquired by [[convergent evolution]].<ref name=xuetal2004/>

===Soft tissue reconstruction===
A comparative analysis of the teeth suggests that tyrannosaurids, as well as the other large theropods, had lips that protected their teeth from external damage. This anatomical feature gave these animals more visual resemblance to [[lepidosauria|lepidosaurs]] than to closely related crocodilians.<ref>{{cite journal|date=30 March 2023|title=Theropod dinosaur facial reconstruction and the importance of soft tissues in paleobiology|author=Thomas M. Cullen, Derek William Larson, Mark P Witton, Diane Scott, Tea Maho, Kirstin S. Brink, David C Evans, Robert Reisz|journal=Science|volume=379|issue=6639|pages=1348–1352 |doi=10.1126/science.abo7877|pmid=36996202 |bibcode=2023Sci...379.1348C |doi-access=free}}</ref>

==Classification==
The name '''Deinodontidae''' was coined by [[Edward Drinker Cope]] in 1866 for this family,<ref name=cope1966>{{cite journal | author = Cope E.D. | year = 1866 | title = Discovery of a gigantic dinosaur in the Cretaceous of New Jersey | journal = Proceedings of the Academy of Natural Sciences of Philadelphia | volume = 18 | pages = 275–279 }}</ref> and continued to be used in place of the newer name Tyrannosauridae through the 1960s.<ref name=maleev1955>{{cite journal | author = Maleev E.A. | year = 1955 | title = New carnivorous dinosaurs from the Upper Cretaceous Mongolia | journal = [[Doklady Akademii Nauk SSSR]] | volume = 104 | issue = 5| pages = 779–783 }}</ref> The type genus of the Deinodontidae is ''[[Deinodon]]'', which was named after isolated teeth from [[Montana]].<ref name=leidy1856>{{Cite journal|last=Leidy |first=Joseph |author-link=Joseph Leidy |year=1856 |title=Notice of remains of extinct reptiles and fishes, discovered by Dr. F.V. Hayden in the badlands of the Judith River, Nebraska Territory |journal=Proceedings of the Academy of Natural Sciences of Philadelphia |volume=8 |pages=72–73}}</ref> However, in a 1970 review of North American tyrannosaurs, [[Dale Russell]] concluded that ''Deinodon'' was not a valid taxon, and used the name Tyrannosauridae in place of Deinodontidae, stating that this was in accordance with [[International Code of Zoological Nomenclature|ICZN]] rules.<ref name=russell1970/> Therefore, Tyrannosauridae is preferred by modern experts.<ref name=carpenter1992/> A petition to officially conserve the family Tyrannosauridae and suppress the family Deinodontidae was submitted to the [[International Commission on Zoological Nomenclature]] (ICZN) in 2020,<ref>{{cite journal|author=Yun, C.-G.|year=2020|title=Case 3815 – Tyrannosauridae Osborn, 1906 (Dinosauria, Theropoda): proposed conservation by reversal of precedence with Deinodontidae Cope, 1866 and Dryptosauridae Marsh, 1890|journal=The Bulletin of Zoological Nomenclature|volume=77|issue=4|pages=29–34|doi=10.21805/bzn.v77.a008}}</ref> which was approved in 2024.<ref>{{cite journal|title=Opinion 2511 (Case 3815) – Tyrannosauridae Osborn, 1906 (Dinosauria, Theropoda): usage conserved by reversing precedence with Deinodontidae Cope, 1866 and Dryptosauridae Marsh, 1890|journal=The Bulletin of Zoological Nomenclature|volume=81|issue=1|pages=156–157|doi=10.21805/bzn.v81.a034|date=December 2024}}</ref>

''Tyrannosaurus'' was named by [[Henry Fairfield Osborn]] in 1905, along with the family Tyrannosauridae.<ref name=osborn1905>{{Cite journal|last=Osborn |first=Henry F. |author-link=Henry Fairfield Osborn |year=1905 |title=''Tyrannosaurus'' and other Cretaceous carnivorous dinosaurs |journal=Bulletin of the American Museum of Natural History |volume=21 |pages=259–265 |doi=10.1111/j.1468-5965.2007.00735_17.x|issue=3|hdl=2246/1464 }}</ref> The name is derived from the [[Ancient Greek]] words ''τυραννος'' (''{{lang|grc-Latn|tyrannos}}'') ('tyrant') and {{lang|grc|σαυρος}} (''{{lang|grc-Latn|sauros}}'') ('lizard'). The very common [[suffix]] ''-idae'' is normally appended to [[zoology|zoological]] family names and is derived from the Greek suffix ''-ιδαι'' ''-{{lang|grc-Latn|idai}}'', which indicates a plural noun.<ref name=liddellscott>{{Cite book |last=Liddell |first=Henry G. |author-link=Henry Liddell |author2=Scott, Robert |author-link2=Robert Scott (philologist) |year=1980 |title=Greek-English Lexicon |edition=Abridged |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-910207-5 |url=https://archive.org/details/lexicon00lidd }}</ref>

===Taxonomy===
[[File:Tarbosaurus and Tyrannosaurus.jpg|thumb|Diagram showing the differences between a generalised ''Tarbosaurus'' (A) and ''Tyrannosaurus'' (B) skull]]
Tyrannosauridae is a [[family (biology)|family]] in rank-based [[Linnaean taxonomy]], within the [[Taxonomic rank|superfamily]] [[Tyrannosauroidea]] and the [[Order (biology)|suborder]] [[Theropoda]].

Tyrannosauridae is uncontroversially divided into two subfamilies. [[Albertosaurinae]] comprises the North American genera ''[[Albertosaurus]]'' and ''[[Gorgosaurus]]'', while [[Tyrannosaurinae]] includes ''[[Daspletosaurus]]'', ''[[Teratophoneus]]'', ''[[Bistahieversor]]'', ''[[Tarbosaurus]]'', ''[[Nanuqsaurus]]'', ''[[Zhuchengtyrannus]]'', and ''[[Tyrannosaurus]]'' itself.<ref name="FT2014">{{Cite journal| last1 = Fiorillo | first1 = A. R. | author-link = Anthony Fiorillo| last2 = Tykoski | first2 = R. S. | author-link2 = Ronald Tykoski| year = 2014| title = A Diminutive New Tyrannosaur from the Top of the World| editor-last = Dodson| editor-first = Peter| editor-link = Peter Dodson| journal = [[PLoS ONE]]| volume = 9| issue = 3| article-number = e91287| doi = 10.1371/journal.pone.0091287| ref = {{sfnRef|Fiorillo & Tykoski|2014}} | pmid=24621577 | pmc=3951350| bibcode = 2014PLoSO...991287F| doi-access = free }}</ref> Some authors include the species ''Gorgosaurus libratus'' in the genus ''Albertosaurus'' and ''Tarbosaurus bataar'' in the genus ''Tyrannosaurus'',<ref name=carretal2005/><ref name=carpenter1992>{{Cite book|last=Carpenter |first=Ken. |author-link=Kenneth Carpenter |year=1992 |chapter=Tyrannosaurids (Dinosauria) of Asia and North America |editor=Mateer, Niall J. |editor2=Chen Peiji |title=Aspects of Nonmarine Cretaceous Geology |location=Beijing |publisher=China Ocean Press |pages=250–268}}</ref><ref name=paul1988>{{Cite book |last=Paul |first=Gregory S. |author-link=Gregory S. Paul |year=1988 |title=Predatory Dinosaurs of the World |location=New York |publisher=Simon & Schuster |pages=[https://archive.org/details/predatorydinosau00paul/page/464 464pp] |isbn=978-0-671-61946-6 |url=https://archive.org/details/predatorydinosau00paul/page/464 }}</ref> while others prefer to retain ''Gorgosaurus'' and ''Tarbosaurus'' as separate genera.<ref name=holtz2004/><ref name=currie2003a/> Albertosaurines are characterized by more slender builds, lower skulls, and proportionately longer [[tibia]]e than tyrannosaurines.<ref name=holtz2004/> In tyrannosaurines, the sagittal crest on the parietals continues forward onto the frontals.<ref name=currie2003a/> In 2014, [[Lü Junchang]] ''et al.'' described the '''Alioramini''' as a [[tribe (biology)|tribe]] within the Tyrannosauridae containing the genera ''[[Alioramus]]'' and ''[[Qianzhousaurus]]''. Their phylogenetic analysis indicated that the tribe was located at the base of the Tyrannosaurinae.<ref name="Junchang2014">{{cite journal |last1=Lü |first1=Junchang |last2=Yi |first2=Laiping |last3=Brusatte |first3=Stephen L. |last4=Yang |first4=Ling |last5=Li |first5=Hua |last6=Chen |first6=Liu |title=A new clade of Asian Late Cretaceous long-snouted tyrannosaurids |journal=Nature Communications |date=2014 |volume=5 |article-number=3788 |doi=10.1038/ncomms4788|pmid=24807588 |doi-access=free |bibcode=2014NatCo...5.3788L }}</ref><ref>{{cite web|url=http://www.cbc.ca/news/technology/pinocchio-rex-long-snouted-tyrannosaur-discovered-in-asia-1.2634651|title=Pinocchio rex long-snouted tyrannosaur discovered in Asia|date=7 May 2014|access-date=8 May 2014|archive-date=2 February 2019|archive-url=https://web.archive.org/web/20190202131420/https://www.cbc.ca/news/technology/pinocchio-rex-long-snouted-tyrannosaur-discovered-in-asia-1.2634651|url-status=live}}</ref> Some authors, such as George Olshevsky and Tracy Ford, have created other subdivisions or tribes for various combinations of tyrannosaurids within the subfamilies.<ref name="Olshevsky1995">{{Cite journal|last=Olshevsky |first=George |author-link=George Olshevsky |year=1995 |title=The origin and evolution of the tyrannosaurids |journal=Kyoryugaku Saizensen [Dino Frontline] |volume=9–10 |pages=92–119}}</ref><ref name=olshevsky&ford2005>{{cite journal |author1=Olshevsky G. |author2=Ford T.L. | year = 1995 | title = The origin and evolution of the Tyrannosauridae, part 2 [in Japanese] | journal = Dino Frontline | volume = 6 | pages = 75–99 }}</ref> However, these have not been phylogenetically defined, and usually consisted of genera that are now considered synonymous with other genera or species.<ref name="currieetal2003"/>

Additional subfamilies have been named for more fragmentary genera, including [[Aublysodon]]tinae and [[Deinodon]]tinae. However, the genera ''[[Aublysodon]]'' and ''[[Deinodon]]'' are usually considered ''[[Nomen dubium|nomina dubia]]'', so they and their eponymous subfamilies are usually excluded from taxonomies of tyrannosaurids. An additional tyrannosaurid, ''[[Raptorex]]'', was initially described as a more primitive tyrannosauroid, but likely represents a juvenile tyrannosaurine similar to ''Tarbosaurus''. However, as it is known only from a juvenile specimen, it is also currently considered a ''nomen dubium''.<ref name=fowleretal2011>{{cite journal | last1 = Fowler | first1 = DW | last2 = Woodward | first2 = HN | last3 = Freedman | first3 = EA | last4 = Larson | first4 = PL | last5 = Horner | first5 = JR | year = 2011 | title = Reanalysis of "Raptorex kriegsteini": A Juvenile Tyrannosaurid Dinosaur from Mongolia | journal = PLOS ONE | volume = 6 | issue = 6| article-number = e21376 | doi = 10.1371/journal.pone.0021376 | bibcode=2011PLoSO...621376F | pmid=21738646 | pmc=3126816| doi-access = free }}</ref> However, Thomas Carr maintains its validity and finds it to be similar to tyrannosaurines.<ref name=":0">{{Cite journal |last=Carr |first=Thomas D. |date=2022-11-25 |title=A reappraisal of tyrannosauroid fossils from the Iren Dabasu Formation (Coniacian–Campanian), Inner Mongolia, People's Republic of China |journal=Journal of Vertebrate Paleontology |language=en |volume=42 |issue=5 |article-number=e2199817 |bibcode=2022JVPal..42E9817C |doi=10.1080/02724634.2023.2199817 |issn=0272-4634 |doi-access=free}}</ref>

===Phylogeny===
With the advent of [[Phylogenetic nomenclature|phylogenetic taxonomy]] in vertebrate paleontology, Tyrannosauridae has been given several explicit definitions. The original was produced by [[Paul Sereno]] in 1998, and included all tyrannosauroids closer to Tyrannosaurus than to either ''[[Alectrosaurus]]'', ''[[Aublysodon]]'' or ''[[Nanotyrannus]]''.<ref name=sereno1998>{{Cite journal|last=Sereno |first=Paul C. |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, Abhandlungen |volume=210 |pages=41–83|language=de|doi=10.1127/njgpa/210/1998/41 }}</ref> However, ''Nanotyrannus'' is often considered to be a juvenile ''Tyrannosaurus rex'', while ''Aublysodon'' is usually regarded as a ''[[nomen dubium]]'' unsuitable for use in the definition of a [[clade]].<ref name=holtz2004/> Definitions since then have been based on more well-established genera.

In 2001, [[Thomas R. Holtz]] Jr. published a [[cladistic]] analysis of the Tyrannosauridae.<ref name="holtz2001" /> He concluded that there were two [[subfamilies]]: the more primitive [[#Taxonomy|Aublysodontinae]], characterized by [[unserrated]] [[premaxillary]] [[teeth]]; and the [[Tyrannosaurinae]].<ref name="holtz2001" /> The Aublysodontinae included ''Aublysodon'', the "[[Kirtland Formation|Kirtland]] ''Aublysodon''", and ''[[Alectrosaurus]]''.<ref name="holtz2001" /> Holtz also found that ''[[Siamotyrannus]]'' exhibited some of the [[synapomorphies]] of the tyrannosauridae, but lay "outside the <nowiki>[</nowiki>[[Family (biology)|family]]<nowiki>]</nowiki> proper."<ref name="holtz2001" />

Later in the same paper, he proposed that Tyrannosauridae be defined as "all descendants of the most recent common ancestor of ''Tyrannosaurus'' and ''Aublysodon''".<ref name="holtz2001" /> He also criticized definitions previously proposed by other workers, like one proposed by [[Paul Sereno]], that the Tyrannosauridae was "all taxa closer to "Tyrannosaurus" than to ''Alectrosaurus'', ''Aublysodon'', and ''[[Nanotyrannus]]''".<ref name="holtz2001" /> Holtz observed that since ''Nanotyrannus'' was probably a misidentified ''T. rex'' juvenile, Sereno's proposed definition would have the family Tyrannosauridae as a subtaxon of the genus ''Tyrannosaurus''.<ref name="holtz2001" /> Further, his proposed definition of the subfamily Tyrannosaurinae would also be limited to ''Tyrannosaurus''.<ref name="holtz2001">Holtz, TR, Jr. (2001), The phylogeny and taxonomy of the Tyrannosauridae in K Carpenter & D Tanke [eds.], Mesozoic Vertebrate Life. Indiana Univ. Press, pp. 64–83.</ref>

A 2003 attempt by [[Christopher Brochu]] included ''[[Albertosaurus]]'', ''[[Alectrosaurus]]'', ''[[Alioramus]]'', ''[[Daspletosaurus]]'', ''[[Gorgosaurus]]'', ''[[Tarbosaurus]]'' and ''Tyrannosaurus'' in the definition.<ref name=Brochu2003b>{{Cite journal|last=Brochu |first=Christopher R. |author-link=Christopher Brochu |year=2003 |title=Osteology of ''Tyrannosaurus rex'': insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull |journal=Society of Vertebrate Paleontology Memoirs |volume=7 |pages=1–138 |doi=10.2307/3889334 |jstor=3889334 |url=http://publication.plazi.org/id/6603FFA80B5D0D64FFF6AB533D39FF9A }}</ref> Holtz redefined the clade in 2004 to use all of the above as specifiers except for ''Alioramus'' and ''Alectrosaurus'', which his analysis could not place with certainty. However, in the same paper, Holtz also provided a completely different definition, including all theropods more closely related to ''Tyrannosaurus'' than to ''Eotyrannus''.<ref name=holtz2004/> The most recent definition is that of Sereno in 2005, which defined Tyrannosauridae as the least inclusive clade containing ''Albertosaurus'', ''Gorgosaurus'' and ''Tyrannosaurus''.<ref name=sereno2005>{{Cite web |url=http://www.taxonsearch.org/dev/file_home.php |title=Stem Archosauria—TaxonSearch |access-date=14 January 2008 |last=Sereno |first=Paul C. |author-link=Paul Sereno |date=7 November 2005 |archive-url=https://web.archive.org/web/20070219102659/http://www.taxonsearch.org/dev/file_home.php |archive-date=19 February 2007 }}</ref>

[[Cladistics|Cladistic]] analyses of tyrannosaurid [[Phylogenetics|phylogeny]] often find ''Tarbosaurus'' and ''Tyrannosaurus'' to be [[Cladistics|sister taxa]], with ''Daspletosaurus'' more basal than either. A close relationship between ''Tarbosaurus'' and ''Tyrannosaurus'' is supported by numerous skull features, including the pattern of [[Suture (anatomical)|sutures]] between certain bones, the presence of a crescent-shaped crest on the postorbital bone behind each eye, and a very deep maxilla with a noticeable downward curve on the lower edge, among others.<ref name=holtz2004/><ref name=carretal2005/> An alternative [[hypothesis]] was presented in a 2003 study by [[Philip J. Currie|Phil Currie]] and colleagues, which found weak support for ''Daspletosaurus'' as a basal member of a [[clade]] also including ''Tarbosaurus'' and ''Alioramus'', both from Asia, based on the absence of a bony prong connecting the nasal and lacrimal bones.<ref name=currieetal2003/> ''Alioramus'' was found to be the closest relative of ''Tarbosaurus'' in this study, based on a similar pattern of stress distribution in the skull.

A related study also noted a locking mechanism in the lower jaw shared between the two genera.<ref name=hurumsabath2003>{{Cite journal |last=Hurum |first=Jørn H. |author2=Sabath, Karol. |year=2003 |title=Giant theropod dinosaurs from Asia and North America: Skulls of ''Tarbosaurus bataar'' and ''Tyrannosaurus rex'' compared |journal=Acta Palaeontologica Polonica |volume=48 |issue=2 |pages=161–190 |url=http://www.app.pan.pl/article/item/app48-161.html?pdf=39 |format=abstract |access-date=2008-09-10 |archive-date=2012-03-08 |archive-url=https://web.archive.org/web/20120308104302/http://www.app.pan.pl/article/item/app48-161.html?pdf=39 |url-status=live }}</ref> In a separate paper, Currie noted the possibility that ''Alioramus'' might represent a juvenile ''Tarbosaurus'', but stated that the much higher tooth count and more prominent nasal crests in ''Alioramus'' suggest it is a distinct genus. Similarly, Currie uses the high tooth count of ''[[Nanotyrannus]]'' to suggest that it may be a distinct genus,<ref name=currie2003a/> rather than a juvenile ''Tyrannosaurus'' as most other experts believe.<ref name=holtz2004/><ref name=carr1999/> However, the discovery and description of ''[[Qianzhousaurus]]'' reveals that ''Alioramus'' is not a close relation to ''Tarbosaurus'', instead belonging to a newly described tribe of tyrannosaurids; the Alioramini. ''Qianzhousaurus'' further reveals that similar long-snouted tyrannosaurids were widely distributed throughout Asia and would have shared the same environment while avoiding competition with larger and more robust tyrannosaurines by hunting different prey.<ref>{{cite web |url=https://www.sciencedaily.com/releases/2014/05/140507100421.htm |title=Newly found dinosaur is long-nosed cousin of Tyrannosaurus rex |work=ScienceDaily |access-date=2018-03-09 |archive-date=2018-03-17 |archive-url=https://web.archive.org/web/20180317102219/https://www.sciencedaily.com/releases/2014/05/140507100421.htm |url-status=live }}</ref>{{Clear}}

{|
| colspan="2" |{{Cladogram|title='''Brusatte & Carr, 2016'''<ref>{{sfnRef|Brusatte & Carr|2016}}</ref>
|clades={{clade| style=font-size:80%;line-height:80%
|label1='''Tyrannosauridae'''
|1={{clade
   |label1=[[Albertosaurinae]]
   |1={{clade
      |1=''[[Gorgosaurus]]''
      |2=''[[Albertosaurus]]'' }}
   |label2='''Tyrannosaurinae'''
   |2={{clade
      |1={{clade
      |label1='''Alioramini'''
      |1={{clade
         |1=''[[Qianzhousaurus]]''
         |2={{clade
            |1=''[[Alioramus remotus]]''
            |2=''[[Alioramus altai]]'' }} }} }}
      |2={{clade
         |1={{clade
            |1=''[[Nanuqsaurus]]''
            |2=''[[Teratophoneus]]'' }}
         |2={{clade
            |1=''[[Lythronax]]''
            |2={{clade
               |1={{clade
                  |1=''[[Daspletosaurus torosus]]''
                  |2=''[[Daspletosaurus horneri]]'' }}
               |2={{clade
                  |1=''[[Zhuchengtyrannus]]''
                  |2={{clade
                     |1=''[[Tarbosaurus]]''
                     |2=''[[Tyrannosaurus]]'' }} }} }} }} }} }} }} }} |align=center}}
|-
|{{Cladogram|title='''Fiorillo ''et al.'' 2014'''<ref>{{sfnRef|Fiorillo & Tykoski|2014}}</ref>
|clades={{clade| style=font-size:80%;line-height:80%
|label1='''Tyrannosauridae'''
|1={{clade
   |label1=[[Albertosaurinae]]
   |1={{clade
      |1=''[[Albertosaurus]]''
      |2=''[[Gorgosaurus]]'' }}
   |label2='''Tyrannosaurinae'''
   |2={{clade
      |1={{clade
         |1=''[[Daspletosaurus]]''
         |2=Two Medicine taxon }}
      |2={{clade
         |1=''[[Teratophoneus]]''
         |2={{clade
            |1=''[[Bistahieversor]]''
            |2={{clade
               |1=''[[Lythronax]]''
               |2={{clade
                  |1=''[[Nanuqsaurus]]''
                  |2={{clade
                     |1={{clade
                        |1=''[[Tarbosaurus]]''
                        |2=''[[Zhuchengtyrannus]]'' }}
                     |2=''[[Tyrannosaurus]]'' }} }} }} }} }} }} }} }} }}
|{{Cladogram|title='''Loewen ''et al.'' 2013'''<ref>{{Cite journal | last1 = Loewen | first1 = M.A. | author-link = Mark Loewen| last2 = Irmis | first2 = R.B. | author-link2 = Randall B. Irmis| last3 = Sertich | first3 = J.J.W. | author-link3 = Joseph Sertich| last4 = Currie | first4 = P. J. | author-link4 = Philip J. Currie| last5 = Sampson | first5 = S. D. | author-link5 = Scott D. Sampson| year = 2013| title = Tyrant Dinosaur Evolution Tracks the Rise and Fall of Late Cretaceous Oceans | editor-last = Evans | editor-first = David C| editor-link = David C. Evans (paleontologist)| journal = [[PLoS ONE]] | volume = 8 | issue = 11 | article-number = e79420 | doi = 10.1371/journal.pone.0079420 | pmid = 24223179| pmc = 3819173| ref = {{sfnRef|Loewen ''et al.''|2013}}| bibcode = 2013PLoSO...879420L| doi-access = free }}</ref>
|clades={{clade| style=font-size:80%;line-height:80%
|label1='''Tyrannosauridae'''
|1={{clade
   |1={{clade
      |1=''[[Gorgosaurus]]''
      |2=''[[Albertosaurus]]'' }}
   |label2='''Tyrannosaurinae'''
   |2={{clade
      |1=[[Dinosaur Park Formation|Dinosaur Park]] tyrannosaurid
      |2={{clade
         |1=''[[Daspletosaurus]]''
         |2={{clade
            |1=''[[Daspletosaurus horneri]]''
            |2={{clade
               |1=''[[Teratophoneus]]''
               |2={{clade
                  |1=''[[Bistahieversor]]''
                  |2={{clade
                     |1=''[[Lythronax]]''
                     |2={{clade
                        |1=''[[Tyrannosaurus]]''
                        |2={{clade
                           |1=''[[Tarbosaurus]]''
                           |2=''[[Zhuchengtyrannus]]'' }} }} }} }} }} }} }} }} }} }}
|align=left}}
|}{{Clear}}

==Paleobiology==
{{Main|Physiology of dinosaurs}}

===Growth===
{{Annotated image | float=right | caption=Hypothesized growth curves (body mass versus age) of four tyrannosaurids<ref name="ericksonetal2004"/>
| image=Tyrannosauroid growth curves unlabelled.png | width=370 | image-width=300 | height=250
| image-left=30 | image-top=15
|annotations=
{{Annotation|15|5|Body mass (kg)}}
{{Annotation|5|22|6,000}}
{{Annotation|5|52|5,000}}
{{Annotation|5|85|4,000}}
{{Annotation|5|116|3,000}}
{{Annotation|5|147|2,000}}
{{Annotation|5|178|1,000}}
{{Annotation|85|222|5}}
{{Annotation|127|222|10}}
{{Annotation|173|222|15}}
{{Annotation|216|222|20}}
{{Annotation|262|222|25}}
{{Annotation|308|222|30}}
{{Annotation|158|235|Age (years)}}
{{Annotation|239|67|{{legend2|black|{{=}} ''[[Tyrannosaurus]]''}}}}
{{Annotation|239|87|{{legend2|#66ff66|{{=}} ''[[Daspletosaurus]]''}}}}
{{Annotation|239|107|{{legend2|blue|{{=}} ''[[Gorgosaurus]]''}}}}
{{Annotation|239|127|{{legend2|red|{{=}} ''[[Albertosaurus]]''}}}}
}}
Paleontologist [[Gregory Erickson (paleontologist)|Gregory Erickson]] and colleagues have studied the growth and life history of tyrannosaurids. Analysis of bone [[histology]] can determine the age of a specimen when it died. Growth rates can be examined when the age of various individuals are plotted against their size on a graph. Erickson has shown that after a long time as juveniles, tyrannosaurs underwent tremendous [[growth spurt]]s for about four years midway through their lives. After the rapid growth phase ended with [[sexual maturity]], growth slowed down considerably in adult animals. A tyrannosaurid growth curve is S-shaped, with the maximum growth rate of individuals around 14 years of age.<ref name=ericksonetal2004/>
[[File:Juvenile Tyrannosaurus skull LACM.jpg|left|upright|thumb|Skull of a juvenile ''T. rex'' formerly classified as ''Dinotyrannus megagracilis'']]
The ''[[Stygivenator]]'' holotype ([[Los Angeles County Museum of Natural History|LACM]] 28471, the "Jordan theropod"), possibly a juvenile ''T. rex'', is estimated to have weighed only {{convert|29.9|kg}} at only 2 years old, while one of the largest ''T. rex'' specimens, such as [[Field Museum of Natural History|FMNH]] PR2081 ("[[Sue (dinosaur)|Sue]]"), most likely weighed about {{convert|5654|kg|abbr=on}}, estimated to have been 28 years old, an age which may have been close to the maximum for the species.<ref name=ericksonetal2004>{{Cite journal |author=Erickson, Gregory M. |author2=Makovicky, Peter J. |author3=Currie, Philip J. |author-link3=Philip J. Currie |author4=Norell, Mark A. |author5=Yerby, Scott A. |author6=Brochu, Christopher A. |year=2004 |title=Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs |journal=Nature |volume=430 |issue=7001 |pages=772–775 |doi=10.1038/nature02699 |pmid=15306807 |first1=GM |quote=Sampled longevities for T. rex ranged from 2 to 28 years |bibcode=2004Natur.430..772E |s2cid=4404887 |url=http://doc.rero.ch/record/15279/files/PAL_E2578.pdf |archive-date=2020-07-14 |access-date=2023-01-07 |archive-url=https://web.archive.org/web/20200714024211/http://doc.rero.ch/record/15279/files/PAL_E2578.pdf |url-status=live }}{{Erratum|doi=10.1038/nature16487|pmid=26675726|http://retractionwatch.com/2016/03/01/high-profile-critic-slams-nature-letters-about-dinosaur-growth-following-corrections/ ''Retraction Watch''}} and corresponding body mass estimates ranged from 29.9 to 5654 kg</ref> ''T. rex'' juveniles remained under {{convert|1800|kg|abbr=on}} until approximately 14 years of age, when body size began to increase dramatically. During this rapid growth phase, a young ''T. rex'' would gain an average of {{convert|600|kg|abbr=on}} a year for the next four years. This slowed after 16 years, and at 18 years of age, the curve plateaus again, indicating that growth slowed dramatically.<ref name="hornerpadian2004">{{Cite journal|author1=Horner, J.R.  |author2=Padian, K. |name-list-style=amp |year=2004|title=Age and growth dynamics of Tyrannosaurus rex|journal=Proceedings of the Royal Society of London B|pmid=15347508|volume=271|issue=1551|pmc=1691809|pages=1875–1880|doi=10.1098/rspb.2004.2829}}</ref> For example, only {{convert|600|kg|abbr=on}} separated the 28-year-old "Sue" from a 22-year-old [[Canada|Canadian]] specimen ([[Royal Tyrrell Museum of Palaeontology|RTMP]] 81.12.1).<ref name="ericksonetal2004"/> This sudden change in growth rate may indicate physical maturity, a hypothesis that is supported by the discovery of medullary tissue in the [[femur]] of an 18-year-old ''T. rex'' from Montana ([[Museum of the Rockies|MOR]] 1125, also known as "B-rex").<ref name=LW08>{{Cite journal|last=Lee |first=Andrew H. |author2=Werning, Sarah |year=2008 |title=Sexual maturity in growing dinosaurs does not fit reptilian growth models |journal=Proceedings of the National Academy of Sciences |volume=105 |issue=2 |pages=582–587 |doi=10.1073/pnas.0708903105 |pmid=18195356 |pmc=2206579|bibcode=2008PNAS..105..582L |doi-access=free }}</ref> Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age.<ref name="schweitzeretal2005">{{Cite journal|author=Schweitzer, M.H., Wittmeyer, J.L., & Horner, J.R.|year=2005|title=Gender-specific reproductive tissue in ratites and ''Tyrannosaurus rex''|journal=Science|volume=308|pages=1456–1460|doi=10.1126/science.1112158|pmid=15933198|issue=5727|bibcode=2005Sci...308.1456S|s2cid=30264554}}</ref>

Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.<ref name="ericksonetal2006">{{Cite journal|author=Erickson, G.M., Currie, P.J., Inouye, B.D., & Winn, A.A.|year=2006|title=Tyrannosaur life tables: an example of nonavian dinosaur population biology|journal=Science|volume=313|pages=213–217|doi=10.1126/science.1125721|pmid=16840697|issue=5784|bibcode=2006Sci...313..213E|s2cid=34191607}}</ref> Compared to albertosaurines, ''Daspletosaurus'' showed a faster growth rate during the rapid growth period due to its higher adult weight. The maximum growth rate in ''Daspletosaurus'' was {{convert|180|kg}} per year, based on a mass estimate of {{convert|1800|kg|abbr=on}} in adults. Other authors have suggested higher adult weights for ''Daspletosaurus''; this would change the magnitude of the growth rate, but not the overall pattern.<ref name=ericksonetal2004/> The youngest known ''Albertosaurus'' is a two-year-old discovered in the Dry Island bonebed, which would have weighed about {{convert|50|kg|abbr=on}} and measured slightly more than {{convert|2|m|ft}} in length. The {{convert|10|m|adj=on}} specimen from the same quarry is the oldest and largest known, at 28 years of age. The fastest growth rate is estimated to occur around 12–16 years of age, reaching {{convert|122|kg|abbr=on}} per year, based on a {{convert|1300|kg|abbr=on}} adult, which is about a fifth of the rate for ''T.-rex''. For ''Gorgosaurus'', the calculated maximum growth rate is about {{convert|110|kg}} during the rapid growth phase, which is comparable to that of ''Albertosaurus''.<ref name=ericksonetal2004/><!--A juvenile specimen of ''[arbosaurus'', found in [[Mongolia]] 2006 (dated about 70 million years old), is believed to have died at an age of about 5 years, and measures about {{convert|2|m|ft|sigfig=1}} long.<ref>{{cite web|url=http://scienceblogs.com/laelaps/2008/07/a_new_juvenile_tarbosaurus.php|title=A new juvenile Tarbosaurus|work=Laelaps}}</ref> Some other specimens of different sizes has been found,<ref>{{cite web|url=http://www.dinocasts.com/prod_productDetails.asp?ProductId=262|title=DinoCasts.com - Juvenile Tarbosaurus bataar cast}}</ref><ref>{{cite web|url=http://www.dinocasts.com/prod_productDetails.asp?ProductId=169|title=DinoCasts.com -}}</ref> but their age at death has not been determined.-->
<!--The discovery of an embryonic tyrannosaur of unknown genera suggests that tyrannosaurids developed their distinctive skeletal features while developing in the egg. Furthermore, the size of the specimen, a 1.1-inch dentary from the lower jaw found in [[Montana]] in 1983 and described in 2020, suggests that neonate tyrannosaurids were born with skulls the size of a [[chicken]]. The specimen's size and developmental stage at the time of death combined with a lack of eggshell fragments may also suggest that tyrannosaurids laid soft-shelled eggs similar to some other dinosaur genera such as ''[[Mussaurus]]'' and ''[[Protoceratops]]''.<ref>https://www.livescience.com/baby-embryonic-tyrannosaur-fossils.html {{Bare URL inline|date=November 2021}}</ref>-->

The discovery of an embryonic tyrannosaur of an as-yet-unknown genus suggests that tyrannosaurids developed their distinctive skeletal features while developing in the egg. Furthermore, the size of the specimen, a {{convert|1.1|in|cm|abbr=on}} dentary from the lower jaw found in the [[Two Medicine Formation]] of Montana in 1983 and a foot claw found in the [[Horseshoe Canyon Formation]] in 2018 and described in 2020, suggests that neonate tyrannosaurids were born with skulls the size of a mouse or similarly sized rodents and may have been roughly the size of a small dog at birth. The jaw specimen is believed to have come from an animal roughly {{Convert|2.5|ft|m|abbr=on}} while the claw is believed to belong to a specimen measuring around {{convert|3|ft|m|abbr=on}}. While eggshells have not been found in association with either specimen, the location where these neonate tyrannosaurids were uncovered suggests these animals were using the same nest sites as other species they lived with and preyed upon.<ref>{{Cite web|url=https://www.nationalgeographic.com/science/2020/10/first-tyrannosaur-embryo-fossils-revealed/|title=First tyrannosaur embryo fossils revealed|date=October 19, 2020|website=Science|access-date=November 23, 2020|archive-date=December 5, 2020|archive-url=https://web.archive.org/web/20201205015329/https://www.nationalgeographic.com/science/2020/10/first-tyrannosaur-embryo-fossils-revealed/}}</ref> The lack of eggshells associated with these specimens has also opened up speculation to the possibility that tyrannosaurids laid soft-shelled eggs as the genera ''[[Mussaurus]]'' and ''[[Protoceratops]]'' are believed to have done.<ref>{{Cite web|url=https://www.livescience.com/baby-embryonic-tyrannosaur-fossils.html|title=1st of their kind baby tyrannosaur fossils unearthed|first=Laura|last=Geggel|website=livescience.com|date=15 October 2020|access-date=17 October 2020|archive-date=17 October 2020|archive-url=https://web.archive.org/web/20201017201213/https://www.livescience.com/baby-embryonic-tyrannosaur-fossils.html|url-status=live}}</ref>

Fossil footprints from the Wapiti Formation suggest that as tyrannosaurids grew, the feet became wider with thicker toes to support their weight. The broader feet suggest that adult tyrannosaurids were slower-moving than their offspring.<ref>{{Cite web|url=http://theconversation.com/fat-footed-tyrannosaur-parents-couldnt-keep-up-with-their-skinnier-offspring-fossil-footprints-reveal-154188|title=Fat-footed tyrannosaur parents couldn't keep up with their skinnier offspring, fossil footprints reveal|first1=Nathan James|last1=Enriquez|first2=Nicolas|last2=Campione|first3=Phil|last3=Bell|website=The Conversation|date=21 April 2021 |access-date=2021-04-28|archive-date=2021-04-26|archive-url=https://web.archive.org/web/20210426230718/https://theconversation.com/fat-footed-tyrannosaur-parents-couldnt-keep-up-with-their-skinnier-offspring-fossil-footprints-reveal-154188|url-status=live}}</ref><ref>{{Cite journal|title=Exploring possible ontogenetic trajectories in tyrannosaurids using tracks from the Wapiti Formation (upper Campanian) of Alberta, Canada|first1=Nathan J.|last1=Enriquez|first2=Nicolás E.|last2=Campione|first3=Tom|last3=Brougham|first4=Federico|last4=Fanti|first5=Matt A.|last5=White|first6=Robin L.|last6=Sissons|first7=Corwin|last7=Sullivan|first8=Matthew J.|last8=Vavrek|first9=Phil R.|last9=Bell|date=April 21, 2021|journal=Journal of Vertebrate Paleontology|volume=40|issue=6|article-number=e1878201|doi=10.1080/02724634.2021.1878201|doi-access=|s2cid=234814620 }}</ref>

===Life history===
[[Image:Gorgosaurus death pose.jpg|thumb|Nearly complete skeleton of a subadult ''Gorgosaurus libratus'', from the [[Royal Tyrrell Museum of Palaeontology]]]]
The end of the rapid growth phase suggests the onset of [[sexual maturity]] in ''Albertosaurus'', although growth continued at a slower rate throughout the animals' lives.<ref name=ericksonetal2004/><ref name=ericksonetal2006/> Sexual maturation while still actively growing appears to be a shared trait among small<ref name=ericksonetal2007>{{Cite journal|last1=Erickson |first1=Gregory M. |last2= Curry Rogers|first2=Kristi |last3=Varricchio |first3=David J. |last4=Norell |first4=Mark |last5=Xu |first5=Xing |year=2007 |title=Growth patterns in brooding dinosaurs reveals the timing of sexual maturity in non-avian dinosaurs and genesis of the avian condition |journal=Biology Letters |volume=3 |pages=558–561 |doi=10.1098/rsbl.2007.0254 |pmid=17638674 |issue=5 |pmc=2396186}}</ref> and large<ref name=lee_werning2008>{{Cite journal|last=Lee |first=Andrew H. |author2=Werning, Sarah |year=2008 |title=Sexual maturity in growing dinosaurs does not fit reptilian growth models |journal=PNAS |volume=105 |pages=582–587 |doi=10.1073/pnas.0708903105 |pmid=18195356 |issue=2 |pmc=2206579|bibcode=2008PNAS..105..582L |doi-access=free }}</ref> dinosaurs as well as in large mammals, such as humans and [[elephant]]s.<ref name=lee_werning2008/> This pattern of relatively early sexual maturation differs strikingly from the pattern in birds, which delay their sexual maturity until after they have finished growing.<ref name=lee_werning2008/><ref name=ricklefs2007>{{Cite journal|last=Ricklefs |first=Robert E. |year=2007 |title=Tyrannosaur ageing |journal=Biology Letters |volume=3 |issue=2 |pages=214–217 |doi=10.1098/rsbl.2006.0597 |pmid=17284406 |pmc=2375931}}</ref>

By tabulating the number of specimens of each age group, Erickson and his colleagues were able to draw conclusions about life history in tyranosauridae populations. Their analysis showed that while juveniles were rare in the fossil record, subadults in the rapid growth phase and adults were far more common. Over half of the known ''T. rex'' specimens appear to have died within six years of reaching sexual maturity, a pattern that is also seen in other tyrannosaurs and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. While this could be due to preservation or collection [[Biased sample|biases]], Erickson hypothesized that the difference was due to low mortality among juveniles over a certain size, which is also seen in some modern large mammals, like [[elephant]]s. This low mortality may have resulted from a lack of predation, since tyrannosaurs surpassed all contemporaneous predators in size by the age of two. Paleontologists have not found enough ''Daspletosaurus'' remains for a similar analysis, but Erickson notes that the same general trend seems to apply.<ref name=ericksonetal2006/>

The tyrannosaurids spent as much as half its life in the juvenile phase before ballooning up to near-maximum size in only a few years.<ref name=ericksonetal2004/> This, along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods, suggests these niches may have been filled by juvenile tyrannosaurids. This is seen in modern [[Komodo dragon]]s, where hatchlings start off as tree-dwelling [[insectivore]]s and slowly mature into massive [[apex predator]]s capable of taking down large vertebrates.<ref name=holtz2004/> For example, ''Albertosaurus'' have been found in aggregations that some have suggested to represent mixed-age [[pack hunter|packs]].<ref name=tankecurrie1998/><ref name=currieetal2005/>

===Locomotion===
Locomotion abilities are best studied for ''Tyrannosaurus'', and there are two main issues concerning this: how well it could turn; and what its maximum straight-line speed was likely to have been. ''Tyrannosaurus'' may have been slow to turn, possibly taking one to two seconds to turn only 45° – an amount that humans, being vertically oriented and tail-less, can spin in a fraction of a second.<ref>{{cite web |url=http://www.cosmosmagazine.com/node/1381 |title=Tyrannosaurus had poor turning circle |access-date=2007-09-25 |url-status=bot: unknown |archive-url=https://web.archive.org/web/20120507053958/http://www.cosmosmagazine.com/node/1381 |archive-date=May 7, 2012 }}</ref> The cause of the difficulty is [[Moment of inertia|rotational inertia]], since much of ''Tyrannosaurus''{{'}}s mass was some distance from its center of gravity, like a human carrying a heavy timber.<ref name="CarrierWalterLee2000TurningPerformance">{{Cite journal | title=Influence of rotational inertia on turning performance of theropod dinosaurs: clues from humans with increased rotational inertia | journal=Journal of Experimental Biology | issue=Pt 22 | pages=3917–3926 | url=http://jeb.biologists.org/cgi/content/full/204/22/3917 | author=Carrier, D.R., Walter, R.M., and Lee, D.V. | pmid=11807109 | date=15 November 2001 | volume=204 | doi=10.1242/jeb.204.22.3917 | bibcode=2001JExpB.204.3917C | access-date=12 October 2008 | archive-date=6 January 2008 | archive-url=https://web.archive.org/web/20080106180207/http://jeb.biologists.org/cgi/content/full/204/22/3917 | url-status=live | url-access=subscription }}</ref>

Scientists have produced a wide range of maximum speed estimates, mostly around {{convert|11|m/s|mph}}, but a few as low as {{convert|5|–|11|m/s|mph}}, and a few as high as {{convert|20|m/s|mph}}. Researchers have to rely on various estimating techniques because, while there are many [[trackway|tracks]] of very large theropods walking, so far none have been found of very large theropods running—and this absence ''may'' indicate that they did not run.<ref name="Hutchinson, J.R. 2004 441–461">{{Cite journal |author=Hutchinson, J.R. |title=Biomechanical Modeling and Sensitivity Analysis of Bipedal Running Ability. II. Extinct Taxa |journal=Journal of Morphology |volume=262 |issue=1 |pages=441–461 |year=2004 |url=http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf |doi=10.1002/jmor.10240 |pmid=15352202 |bibcode=2004JMorp.262..441H |s2cid=15677774 |archive-url=https://web.archive.org/web/20081031093050/http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf |archive-date=2008-10-31 }}</ref>

{{Annotated image/Skeletal anatomy of T rex right leg | float=left}}
<!--  ********  [[Image:T Rex Leg Bones.png|thumb|212px|left|Skeletal anatomy of a ''T. rex'' right leg.]]
********  -->
Jack Horner and Don Lessem argued in 1993 that ''Tyrannosaurus'' was slow and probably could not run (no airborne phase in mid-stride).<ref name="hornerlessem1993">{{Cite book |first=John R. |last=Horner |author-link=Jack Horner (paleontologist) |author2=Don Lessem |title=The complete T. rex |publisher=[[Simon & Schuster]] |location=[[New York City]] |year=1993 |pages=[https://archive.org/details/completetrexhows00horn/page/120 120] |isbn=978-0-671-74185-3 |author2-link=Don Lessem |url=https://archive.org/details/completetrexhows00horn/page/120 }}</ref> However, Holtz (1998) concluded that tyrannosaurids and their close relatives were the fastest large theropods.<ref name="Holtz1998TaxonomyCoelurosauria">{{Cite journal |first=Thomas R. |last=Holtz |author-link=Thomas R. Holtz Jr. |title=Phylogenetic taxonomy of the Coelurosauria (Dinosauria; Theropoda) |journal=Journal of Paleontology |date=1 May 1996 |volume=70 |issue=3 |pages=536–538 |url=http://jpaleontol.geoscienceworld.org/cgi/content/abstract/70/3/536 |access-date=3 October 2008 |doi=10.1017/S0022336000038506 |bibcode=1996JPal...70..536H |s2cid=87599102 |archive-date=26 October 2008 |archive-url=https://web.archive.org/web/20081026053239/http://jpaleontol.geoscienceworld.org/cgi/content/abstract/70/3/536 |url-status=live |url-access=subscription }}</ref> Christiansen (1998) estimated that the leg bones of ''Tyrannosaurus'' were not significantly stronger than those of elephants, which are relatively limited in their top speed and never actually run (there is no airborne phase), and hence proposed that the dinosaur's maximum speed would have been about {{convert|11|m/s|mph}}, which is about the speed of a human sprinter.<ref name="Christiansen1998Strength">{{Cite journal |author=Christiansen, P. |title=Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential |journal=Gaia |year=1998 |volume=15 |pages=241–255 |url=http://www.mnhn.ul.pt/geologia/gaia/19.pdf |issn=0871-5424 |access-date=2008-10-12 |archive-date=2008-10-31 |archive-url=https://web.archive.org/web/20081031093050/http://www.mnhn.ul.pt/geologia/gaia/19.pdf |url-status=live }}</ref> Farlow and colleagues (1995) have argued that a 6- to 8-ton ''Tyrannosaurus'' would have been critically or even fatally injured if it had fallen while moving quickly, since its torso would have slammed into the ground at a deceleration of 6&nbsp;''g'' (six times the acceleration due to gravity, or about 60 metres/s<sup>2</sup>) and its tiny arms could not have reduced the impact.<ref name=farlowetal1995>{{Cite journal |doi=10.1080/02724634.1995.10011257 |last=Farlow |first=James O. |author-link=James Farlow |author2=Smith, Matthew B. |author3=Robinson, John M. |year=1995 |title=Body mass, bone "strength indicator", and cursorial potential of ''Tyrannosaurus rex'' |journal=Journal of Vertebrate Paleontology |volume=15 |issue=4 |pages=713–725 |bibcode=1995JVPal..15..713F |url=http://www.vertpaleo.org/publications/jvp/15-713-725.cfm |archive-url=https://web.archive.org/web/20081023063102/http://www.vertpaleo.org/publications/jvp/15-713-725.cfm |archive-date=2008-10-23 |url-access=subscription }}</ref><ref>[https://www.newscientist.com/article/mg14819982.600-the-bigger-they-come-the-harder-they-fall.html "The bigger they come, the harder they fall"] {{Webarchive|url=https://web.archive.org/web/20150531201705/http://www.newscientist.com/article/mg14819982.600-the-bigger-they-come-the-harder-they-fall.html |date=2015-05-31 }} New Scientist, 7 October 1995, p. 18.</ref> However, [[giraffe]]s have been known to gallop at {{Convert|50|km/h|abbr=on}}, despite the risk that they might break a leg or worse, which can be fatal even in a "safe" environment such as a zoo.<ref>{{Cite web |url=http://www.wildlifesafari.info/giraffe.html |publisher=WildlifeSafari.info |title=Giraffe |access-date=29 April 2006 |archive-date=12 June 2010 |archive-url=https://web.archive.org/web/20100612080401/http://www.wildlifesafari.info/giraffe.html |url-status=live }}</ref><ref>{{Cite web|url=http://www.zoo.org/zoo_info/history/chapters/history4.html |title=The History of Woodland Park Zoo&nbsp;— Chapter 4 |access-date=29 April 2006 |archive-url=https://web.archive.org/web/20070602141617/http://www.zoo.org/zoo_info/history/chapters/history4.html |archive-date=June 2, 2007 }}</ref> Thus it is quite possible that ''Tyrannosaurus'' also moved fast when necessary and had to accept such risks; this scenario has been studied for ''Allosaurus'' too.<ref name="Alexander2006DinoBioMechanics">{{Cite journal|author=Alexander, R.M. |title=Dinosaur biomechanics |journal=Proc Biol Sci |date=August 7, 2006 |volume=273 |issue=1596 |pages=1849–1855 |doi=10.1098/rspb.2006.3532 |pmid=16822743 |pmc=1634776}}</ref><ref name="Hanna2002MultipleInjuriesBigAl">{{Cite journal|last=Hanna |first=Rebecca R. |year=2002 |title=Multiple injury and infection in a sub-adult theropod dinosaur (''Allosaurus fragilis'') with comparisons to allosaur pathology in the Cleveland-Lloyd Dinosaur Quarry collection |journal=Journal of Vertebrate Paleontology |volume=22 |issue=1 |pages=76–90 |doi=10.1671/0272-4634(2002)022[0076:MIAIIA]2.0.CO;2|s2cid=85654858 |issn=0272-4634}} catalogues the injuries of the ''[[Allosaurus]]'' known as "[[The Ballad of Big Al|Big Al]]" - at least one was attributed to a fall.</ref> Most recent research on ''Tyrannosaurus'' locomotion does not narrow down speeds further than a range from {{convert|17|to|40|km/h|abbr=on}}, i.e. from walking or slow running to moderate-speed running.<ref name="Hutchinson, J.R. 2004 441–461"/><ref name="HutchinsonGarcia2002TrexSlow">{{Cite journal |author8=Hutchinson, J. R. and Garcia, M. |date=28 February 2002 |title=''Tyrannosaurus'' was not a fast runner |journal=Nature |volume=415 |pages=1018–1021 |doi=10.1038/4151018a |author=Hutchinson, John R. |pmid=11875567 |last2=Garcia |first2=M |issue=6875 |bibcode=2002Natur.415.1018H |s2cid=4389633 |url=http://researchonline.rvc.ac.uk/id/eprint/1204/ |archive-date=9 August 2022 |access-date=7 January 2023 |archive-url=https://web.archive.org/web/20220809012102/https://researchonline.rvc.ac.uk/id/eprint/1204/ |url-status=live |url-access=subscription }}</ref><ref name="dinocards7">Hajdul, R. (1997). Tendons. ''Dinosaur Cards''. Orbis Publishing Ltd. D36044311.</ref> A computer model study in 2007 estimated running speeds, based on data taken directly from fossils, and claimed that ''T. rex'' had a top running speed of {{convert|8|m/s|mph}}.<ref name="SellersManning2007ProcRSocB">{{Cite journal |title=Estimating dinosaur maximum running speeds using evolutionary robotics |journal=Proc. R. Soc. B |doi=10.1098/rspb.2007.0846 |date=July 2007 |url=http://dinonews.net/rubriq/articles.php5?action=open&ref=2007_sellers_speed |author1=Sellers, W.I. |author2=Manning, P.L. |name-list-style=amp |volume=274 |pmid=17711833 |issue=1626 |pmc=2279215 |pages=2711–6 |access-date=2008-10-12 |archive-date=2011-02-07 |archive-url=https://web.archive.org/web/20110207142321/http://dinonews.net/rubriq/articles.php5?action=open&ref=2007_sellers_speed |url-status=live }} This may be a preliminary version of Sellers, W. I., Manning, P.L., Crompton, R.H. and Codd, J.R.,. (2007), "Exploring elastic energy storage effects in bipedal locomotion using evolutionary robotics", ''Journal of Biomechanics'', in-review</ref><ref>[https://news.bbc.co.uk/2/hi/science/nature/6956867.stm Liz Seward: "T. rex 'would outrun footballer'"] . ''BBC News'' website, Tuesday, 21 August 2007. The article quotes Dr Bill Sellers, University of Manchester, co-author of a paper published in ''Proceedings of the Royal Society B''. Retrieved 22 August 2007.</ref> (Probably a juvenile individual.<ref name=compysize>{{Cite journal|last=Callison|first=G.|author2=H. M. Quimby |year=1984|title= Tiny dinosaurs: Are they fully grown? |journal=Journal of Vertebrate Paleontology|volume=3 |pages=200–209|doi=10.1080/02724634.1984.10011975|issue=4|bibcode=1984JVPal...3..200C }}</ref>)
 
Studies by Eric Snively ''et al.,'' published in 2019 indicate that tyrannosaurids such as ''Tarbosaurus'' and ''Tyrannosaurus'' itself were more manoeuvrable than allosauroids of comparable size due to low rotational inertia compared to their body mass combined with large leg muscles. As a result, it is hypothesized that tyrannosaurids were capable of making relatively quick turns and could likely pivot their bodies more quickly when close to their prey, or that while turning, they could "pirouette" on a single planted foot while the alternating leg was held out in a suspended swing during pursuit. The results of this study potentially could shed light on how agility could have contributed to the success of tyrannosaurid evolution.<ref>{{Cite journal|title=Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods|first1=Eric|last1=Snively|first2=Haley|last2=O'Brien|first3=Donald M.|last3=Henderson|first4=Heinrich|last4=Mallison|first5=Lara A.|last5=Surring|first6=Michael E.|last6=Burns|first7=Thomas R. Holtz|last7=Jr|first8=Anthony P.|last8=Russell|first9=Lawrence M.|last9=Witmer|first10=Philip J.|last10=Currie|first11=Scott A.|last11=Hartman|first12=John R.|last12=Cotton|date=February 21, 2019|journal=PeerJ|volume=7|article-number=e6432|doi=10.7717/peerj.6432|pmid=30809441|pmc=6387760|doi-access=free}}</ref>

Additionally, a 2020 study indicates that tyrannosaurids were exceptionally efficient walkers. Studies by Dececchi ''et al.'', compared the leg proportions, body mass, and the gaits of more than 70 species of theropod dinosaurs including tyrannosaurids. The research team then applied a variety of methods to estimate each dinosaur's top speed when running as well as how much energy each dinosaur expended while moving at more relaxed speeds such as when walking. Among smaller to medium-sized species such as dromaeosaurids, longer legs appear to be an adaptation for faster running, in line with previous results by other researchers. But for theropods weighing over {{convert|1000|kg|lb|abbr=on}}, top running speed is limited by body size, so longer legs instead were found to have correlated with low-energy walking. The results of the study further indicated that smaller theropods evolved long legs for speed as a means to both aid in hunting and escape from larger predators while larger predatory theropods that evolved long legs did so to reduce the energy costs and increase foraging efficiency, as they were freed from the demands of predation pressure due to their role as apex predators. Compared to more basal groups of theropods in the study, tyrannosaurids showed a marked increase in foraging efficiency due to reduced energy expenditures during hunting and scavenging. This likely resulted in tyrannosaurs having a reduced need for hunting forays and requiring less food to sustain themselves as a result. Additionally, the research, in conjunction with studies that show tyrannosaurs were more agile than other large-bodied theropods, indicates they were quite well-adapted to a long-distance stalking approach followed by a quick burst of speed to go for the kill. Analogies can be noted between tyrannosaurids and modern wolves as a result, supported by evidence that at least some tyrannosaurids such as ''Albertosaurus'' were hunting in group settings.<ref>{{Cite journal|doi = 10.1371/journal.pone.0223698|title = The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs|year = 2020|last1 = Dececchi|first1 = T. Alexander|last2 = Mloszewska|first2 = Aleksandra M.|last3 = Holtz|first3 = Thomas R.|last4 = Habib|first4 = Michael B.|last5 = Larsson|first5 = Hans C. E.|journal = PLOS ONE|volume = 15|issue = 5|article-number = e0223698|pmid = 32401793|pmc = 7220109|bibcode = 2020PLoSO..1523698D|doi-access = free}}</ref><ref>{{Cite web|url=https://www.eurekalert.org/pub_releases/2020-05/p-trw051320.php|title=T. rex was a champion walker, super-efficient at lower speeds|website=EurekAlert!|access-date=2020-06-27|archive-date=2020-06-27|archive-url=https://web.archive.org/web/20200627052208/https://www.eurekalert.org/pub_releases/2020-05/p-trw051320.php|url-status=live}}</ref>

===Integument===
{{See also|Feathered dinosaurs}}
[[File:Gorgosaurus.png|thumb|''Gorgosaurus'' restoration with speculative plumage, a trait inferred by [[phylogenetic bracketing]]]]
An ongoing debate in the paleontological community surrounds the extent and nature of tyrannosaurid integumentary covering. Long [[Protein filament|filamentous]] structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous [[Yixian Formation]] and other nearby [[Formation (stratigraphy)|geological formations]] from [[Liaoning]], China.<ref name=zhouetal2003>{{Cite journal|last1=Zhou Zhonghe |author2=Barrett, Paul M. |author3= Hilton, Jason. |year=2003 |title=An exceptionally preserved Lower Cretaceous ecosystem |journal=Nature |volume=421 |issue=6925 |pages=807–814 |doi=10.1038/nature01420 |pmid=12594504 |first1=Z|bibcode=2003Natur.421..807Z |s2cid=4412725 }}</ref> These filaments have usually been interpreted as "protofeathers," [[Homology (biology)|homologous]] with the branched feathers found in birds and [[Feathered dinosaurs|some non-avian theropods]],<ref name=chenetal1998>{{Cite journal|last1=Chen Peiji |author2=Dong Zhiming |author3= Zhen Shuonan. |year=1998 |title=An exceptionally well-preserved theropod dinosaur from the Yixian Formation of China |journal=Nature |volume=391 |issue=6663 |pages=147–152 |doi=10.1038/34356 |first1=Pei-ji |bibcode=1998Natur.391..147C|s2cid=4430927 |url=http://doc.rero.ch/record/14898/files/PAL_E2040.pdf |author2-link=Dong Zhiming }}</ref><ref name=xuetal2003>{{Cite journal|author=Xu Xing |author-link=Xu Xing (paleontologist) |author2=Zhou Zhonghe |last3=Prum |first3=Richard A. |year=2003 |title=Branched integumental structures in Sinornithosaurus and the origin of feathers |journal=Nature |volume=410 |issue=6825 |pages=200–204 |doi=10.1038/35065589 |pmid=11242078 |first1=X |bibcode=2001Natur.410..200X|s2cid=4426803 }}</ref> although other hypotheses have been proposed.<ref name=linghamsoliaretal2007>{{Cite journal|last1=Lingham-Soliar |first1=Theagarten |author-link2=Alan Feduccia|last2=Feduccia |first2=Alan |last3=Wang |first3=Xiaolin |year=2007 |title=A new Chinese specimen indicates that 'protofeathers' in the Early Cretaceous theropod dinosaur Sinosauropteryx are degraded collagen fibres |journal=Proceedings of the Royal Society of London. Series B, Biological Sciences |pmid=17521978 |volume=274 |issue=1620 |pmc=2270928 |pages=1823–1829 |doi=10.1098/rspb.2007.0352}}</ref> A skeleton of ''Dilong'' was described in 2004 that included the first example of "protofeathers" in a tyrannosauroid. Similarly to [[down feather]]s of modern birds, the "protofeathers" found in ''Dilong'' were branched but not [[pennaceous feather|pennaceous]], and may have been used for [[Thermal insulation|insulation]].<ref name=xuetal2004/> The discovery and description of the {{convert|9|m|adj=on}} feathered tyrannosauroid ''[[Yutyrannus]]'' in 2012 indicates the possibility large tyrannosaurids were also feathered as adults.<ref>{{cite web |url=http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |title=Archived copy |access-date=2012-04-04 |archive-url=https://web.archive.org/web/20120417134949/http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |archive-date=2012-04-17 }}</ref>
[[File:Royal Tyrrell Museum 2014.6.JPG|thumb|''Albertosaurus'' sculpture from Royal Tyrrell Museum depicted with featherless skin]]
Based on the principle of [[phylogenetic bracketing]], it was predicted that tyrannosaurids might also possess such feathering. However, a study in 2017 published by a team of researchers in Biology Letters described tyrannosaurid skin impressions collected in Alberta, Montana, and Mongolia, which came from five genera (''Tyrannosaurus'', ''Albertosaurus'', ''Gorgosaurus'', ''Daspletosaurus'' and ''Tarbosaurus'').<ref name="rsbl.royalsocietypublishing.org">{{cite journal | last1 = Bell | first1 = P. R. | last2 = Campione | first2 = N. E. | last3 = Persons | first3 = W. S. | last4 = Currie | first4 = P. J. | last5 = Larson | first5 = P. L. | last6 = Tanke | first6 = D. H. | last7 = Bakker | first7 = R. T. | year = 2017 | 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 | pmid = 28592520 | pmc = 5493735 | doi-access = free }}</ref> Although the skin impressions are small, they are widely dispersed across the post-cranium, being collectively located on the abdomen, thoracic region, ilium, pelvis, tail, and neck. They show a tight pattern of fine, non-overlapping pebbly scales (which co-author Scott Persons compared to those seen on the flanks of a crocodile<ref>http://globalnews.ca/news/3506400/tyrannosaurus-rex-fossil-skin-scales-university-of-alberta/ {{Webarchive|url=https://web.archive.org/web/20170617181635/http://globalnews.ca/news/3506400/tyrannosaurus-rex-fossil-skin-scales-university-of-alberta/ |date=2017-06-17 }} What does a T. Rex feel like? U of A paleontologists find out in new fossil discovery</ref>) and preserve no hints of feathering. The basic texture is composed of tiny "basement scales" approximately 1 to 2&nbsp;mm in diameter, with some impressions showing 7&nbsp;mm "feature scales" interspersed between them. Additional scales can be seen in tyrannosaurid footprints.<ref>Currie, P.J., Badamgarav, D., Koppelhus, E.B. 2003. The First Late Cretaceous Footprints from the Nemegt Locality in the Gobi of Mongolia. Ichnos. Vol.10:1-12.Currie, P.J., Badamgarav, D., Koppelhus, E.B. 2003.</ref> Studies find that the facial integument of tyrannosaurids had scales on the dentary and maxilla, cornified epidermis and armor-like skin on the subordinate regions.<ref>Carr, T. D., Varricchio, D. J., Sedlmayr, J. C., Roberts, E. M., & Moore, J. R. (2017). A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system. ''Scientific Reports'', 7.</ref><ref>{{Cite web |last1=Witton |first1=Mark |last2=Hone |first2=David |date=September 2018 |title=Tyrannosaurid theropods: did they ever smile like crocodiles? |url=https://iris.unito.it/bitstream/2318/1703198/1/SVPCA2018AbstractBooklet.pdf |website=The Annual Symposium of Vertebrate Palaeontology and Comparative Anatomy |access-date=2022-07-18 |archive-date=2022-07-16 |archive-url=https://web.archive.org/web/20220716023044/https://iris.unito.it/bitstream/2318/1703198/1/SVPCA2018AbstractBooklet.pdf |url-status=live }}</ref>

Bell ''et al.'' performed an ancestral character reconstruction based on what is known about integument distribution in tyrannosauroids. Despite an 89% probability that tyrannosauroids started out with feathers, they determined that scaly tyrannosaurids have a 97% probability of being true. The data "provides compelling evidence of an entirely squamous covering in Tyrannosaurus," the team wrote, although they conceded that plumage may have still been present on the dorsal region where skin impressions haven't been found yet. Bell ''et al.'' hypothesizes that the scale impressions of tyrannosaurids are possibly reticula which are secondarily derived from feathers though evidence is needed to support this.<ref name="rsbl.royalsocietypublishing.org"/> However, others argue that this is because of taphonomic bias in tyrannosaurids.<ref>{{Cite journal |last1=Saitta |first1=Evan T. |last2=Fletcher |first2=Ian |last3=Martin |first3=Peter |last4=Pittman |first4=Michael |last5=Kaye |first5=Thomas G. |last6=True |first6=Lawrence D. |last7=Norell |first7=Mark A. |last8=Abbott |first8=Geoffrey D. |last9=Summons |first9=Roger E. |last10=Penkman |first10=Kirsty |last11=Vinther |first11=Jakob |date=2018-11-01 |title=Preservation of feather fibers from the Late Cretaceous dinosaur Shuvuuia deserti raises concern about immunohistochemical analyses on fossils |url=https://dspace.mit.edu/bitstream/handle/1721.1/125319/Saitta_et_al_feather_fibres_OG_AAM.pdf?sequence=2&isAllowed=y |journal=Organic Geochemistry |language=en |volume=125 |pages=142–151 |doi=10.1016/j.orggeochem.2018.09.008 |bibcode=2018OrGeo.125..142S |hdl=1721.1/125319 |s2cid=105753275 |issn=0146-6380 |archive-date=2022-08-29 |access-date=2022-08-29 |archive-url=https://web.archive.org/web/20220829004119/https://dspace.mit.edu/bitstream/handle/1721.1/125319/Saitta_et_al_feather_fibres_OG_AAM.pdf?sequence=2&isAllowed=y |url-status=live }}</ref>

It has yet to be determined why such an integumentary change might have occurred. A precedent for feather loss can be seen in other dinosaur groups such as [[ornithischia]]ns, in which filamentous structures were lost, and scales reappeared.<ref>{{Cite web|url=https://blog.thingswedontknow.com/2014/09/ten-things-we-dont-know-about-tyrannosaurs.html|title=Ten Things We Don't Know about Tyrannosaurs|first=Guest|last=blogger|access-date=2021-01-05|archive-date=2020-09-30|archive-url=https://web.archive.org/web/20200930075917/https://blog.thingswedontknow.com/2014/09/ten-things-we-dont-know-about-tyrannosaurs.html|url-status=live}}</ref> Although gigantism has been suggested as a mechanism, Phil R. Bell, who co-authored the study, noted that the feathered ''Yutyrannus'' overlapped in size with ''Gorgosaurus'' and ''Albertosaurus''. "The problem here is that we have big tyrannosaurs, some with feathers, some without that live in pretty similar climates. So what's the reason for this difference? We really don't know."<ref>{{Cite news |last=Guarino |first=Ben |date=2021-10-27 |title=Tyrannosaurus rex had scaly skin and wasn't covered in feathers, a new study says |language=en-US |newspaper=Washington Post |url=https://www.washingtonpost.com/news/speaking-of-science/wp/2017/06/06/tyrannosaurus-rex-had-scaly-skin-and-wasnt-covered-in-feathers-a-new-study-says/ |access-date=2023-08-07 |issn=0190-8286 |archive-date=2017-06-16 |archive-url=https://web.archive.org/web/20170616111207/https://www.washingtonpost.com/news/speaking-of-science/wp/2017/06/06/tyrannosaurus-rex-had-scaly-skin-and-wasnt-covered-in-feathers-a-new-study-says/ |url-status=live }}</ref>

===Vision===
[[File:Sue TRex Skull Full Frontal.JPG|thumb|upright|The eye-sockets of ''T. rex'' faced mainly forwards, giving it good [[binocular vision]]]]
The eye-sockets of ''Tyrannosaurus'' are positioned so that the eyes would point forward, giving them [[binocular vision]] slightly better than that of modern [[hawk]]s. While predatory theropods in general had binocular vision directly in front of their skull, tyrannosaurs had a significantly larger area of overlap. [[Jack Horner (paleontologist)|Jack Horner]] also pointed out that the tyrannosaur lineage had a history of steadily improving binocular vision. It is hard to see how [[natural selection]] would have favored this long-term trend if tyrannosaurs had been pure scavengers, which would not have needed the advanced [[depth perception]] that [[Stereopsis|stereoscopic vision]] provides.<ref name="Stevens2006Binocular">{{Cite journal |last=Stevens |first=Kent A. |date=June 2006 |title=Binocular vision in theropod dinosaurs |journal=Journal of Vertebrate Paleontology |issue=2 |pages=321–330 |url=http://reocities.com/Athens/Bridge/4602/theropod_binocularvision.pdf |doi=10.1671/0272-4634(2006)26[321:BVITD]2.0.CO;2 |volume=26 |s2cid=85694979 |issn=0272-4634 |archive-url=https://web.archive.org/web/20120323155306/http://reocities.com/Athens/Bridge/4602/theropod_binocularvision.pdf |archive-date=2012-03-23 }}</ref><ref name=jaffe>{{Cite journal |last=Jaffe |first=Eric |date=1 July 2006 |title=Sight for 'Saur Eyes: ''T. rex'' vision was among nature's best |journal=[[Science News]] |volume=170 |issue=1 |url=http://www.sciencenews.org/view/generic/id/7500/title/Sight_for_Saur_Eyes_%3Ci%3ET._rex%3Ci%3E_vision_was_among_natures_best |access-date=6 October 2008 |doi=10.2307/4017288 |jstor=4017288 |pages=3–4 |archive-date=29 September 2012 |archive-url=https://web.archive.org/web/20120929190336/http://www.sciencenews.org/view/generic/id/7500/title/Sight_for_Saur_Eyes_%3Ci%3ET._rex%3Ci%3E_vision_was_among_natures_best |url-status=live |url-access=subscription }}</ref> In modern animals, binocular vision is found mainly in predators (the principal exceptions are [[primate]]s, which need it for leaping from branch to branch). Unlike ''Tyrannosaurus'', ''Tarbosaurus'' had a narrower skull more typical of other tyrannosaurids in which the eyes faced primarily sideways. All of this suggests that ''Tarbosaurus'' relied more on its senses of smell and hearing than on its eyesight.<ref name=savelievalifanov2005>{{Cite journal|last=Saveliev |first=Sergei V. |author2=Alifanov, Vladimir R. |year=2005 |title=A new study of the brain of the predatory dinosaur ''Tarbosaurus bataar'' (Theropoda, Tyrannosauridae) |journal=Paleontological Journal |volume=41 |issue=3 |pages=281–289 |doi=10.1134/S0031030107030070|bibcode=2007PalJ...41..281S |s2cid=53529148 }}</ref> In ''Gorgosaurus'' specimens, the [[orbit (anatomy)|eye socket]] was circular rather than oval or keyhole-shaped as in other tyrannosaurid genera.<ref name=currie2003a/> In ''Daspletosaurus'', this was a tall oval, somewhere in between the circular shape seen in ''Gorgosaurus'' and the 'keyhole' shape of ''Tyrannosaurus''.<ref name=holtz2004/><ref name=currie2003a/><ref name=carr1999>{{Cite journal |doi=10.1080/02724634.1999.10011161 |last=Carr |first=Thomas D. |year=1999 |title=Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria) |journal=Journal of Vertebrate Paleontology |volume=19 |issue=3 |pages=497–520 |bibcode=1999JVPal..19..497C |s2cid=83744433 |url=https://zenodo.org/record/3371479 |access-date=2019-12-02 |archive-date=2020-02-20 |archive-url=https://web.archive.org/web/20200220183407/https://zenodo.org/record/3371479 |url-status=live }}</ref>

=== Facial sensitivity ===
Based on comparisons of [[Osteological correlate|bone texture]] of ''[[Daspletosaurus]]'' with extant [[crocodilians]], a detailed study in 2017 by [[Thomas Carr (paleontologist)|Thomas D. Carr]] ''et al.'' found that tyrannosaurs had large, flat [[reptile scale|scales]] on their [[snouts]].<ref name="ReferenceA">{{Cite journal|last1=Carr|first1=Thomas D.|last2=Varricchio|first2=David J.|last3=Sedlmayr|first3=Jayc C.|last4=Roberts|first4=Eric M.|last5=Moore|first5=Jason R.|date=2017-03-30|title=A new tyrannosaur with evidence for anagenesis and crocodile-like facial sensory system|journal=Scientific Reports|language=en|volume=7|doi=10.1038/srep44942|pmid=28358353|issn=2045-2322|article-number=44942|bibcode=2017NatSR...744942C|pmc=5372470}}</ref><ref name="Complex neuroanatomy in the rostrum of the Isle of Wight theropod Neovenator salerii">{{cite journal |last1=Barker |first1=Chris |last2=Naish |first2=Darren |last3=Katsamenis |first3=Orestis |last4=Dyke |first4=Gareth |title=Complex neuroanatomy in the rostrum of the Isle of Wight theropod Neovenator salerii |journal=Scientific Reports |date=June 16, 2017 |volume=7 |issue=1 |page=3749 |doi=10.1038/s41598-017-03671-3 |pmid=28623335 |pmc=5473926 |bibcode=2017NatSR...7.3749B |doi-access=free }}</ref>
At the center of these [[reptile scale|scales]] were small [[keratin]]ised patches. In [[crocodilians]], such patches cover bundles of [[sensory neurons]] that can detect mechanical, thermal and chemical [[Stimulus (physiology)|stimuli]].<ref>{{Cite journal|last1=Leitch|first1=Duncan B.|last2=Catania|first2=Kenneth C.|date=2012-12-01|title=Structure, innervation and response properties of integumentary sensory organs in crocodilians|journal=Journal of Experimental Biology|language=en|volume=215|issue=23|pages=4217–4230|doi=10.1242/jeb.076836|issn=0022-0949|pmid=23136155|pmc=4074209|bibcode=2012JExpB.215.4217L }}</ref><ref>{{Cite journal|last1=Di-Poï|first1=Nicolas|last2=Milinkovitch|first2=Michel C.|date=2013-07-02|title=Crocodylians evolved scattered multi-sensory micro-organs|journal=EvoDevo|volume=4|issue=1|page=19|doi=10.1186/2041-9139-4-19|pmid=23819918|pmc=3711810|issn=2041-9139 |doi-access=free }}</ref> They proposed that [[tyrannosaurs]] probably also had bundles of [[sensory neurons]] under their facial [[reptile scale|scales]] and may have used them to identify objects, measure the [[temperature]] of their [[nests]] and gently pick-up [[egg]]s and [[hatchlings]].<ref name="ReferenceA"/>

===Bony crests===
[[Image:Alioramus skull steveoc.png|thumb|The skull of ''Alioramus'' with distinct nasal bumps]]
Bony crests are found on the skulls of many theropods, including many tyrannosaurids. ''[[Alioramus]]'', a possible tyrannosaurid from Mongolia, bears a single row of five prominent bony bumps on the nasal bones; a similar row of much lower bumps is present on the skull of ''Appalachiosaurus'', as well as some specimens of ''[[Daspletosaurus]]'', ''Albertosaurus'', and ''Tarbosaurus''.<ref name=carretal2005/> In ''Albertosaurus'', ''Gorgosaurus'' and ''Daspletosaurus'', there is a prominent horn in front of each eye on the lacrimal bone. The lacrimal horn is absent in ''Tarbosaurus'' and ''Tyrannosaurus'', which instead have a crescent-shaped crest behind each eye on the [[Postorbital|postorbital bone]]. These head crests may have been used for [[Display (zoology)|display]], perhaps for species recognition or [[Courtship display|courtship]] behavior.<ref name=holtz2004/>

===Thermoregulation===
''Tyrannosaurus'', like most dinosaurs, was long thought to have an [[ectotherm]]ic ("cold-blooded") reptilian [[metabolism]] but was challenged by scientists like [[Robert T. Bakker]] and [[John Ostrom]] in the early years of the "[[Dinosaur renaissance|Dinosaur Renaissance]]", beginning in the late 1960s.<ref name="bakker1968">{{Cite journal|last=Bakker |first=Robert T. |author-link=Robert T. Bakker |year=1968 |title=The superiority of dinosaurs |journal=Discovery |volume=3 |issue=2 |pages=11–12}}</ref><ref name="bakker1972">{{Cite journal|last=Bakker |first=Robert T. |author-link=Robert T. Bakker |year=1972 |title=Anatomical and ecological evidence of endothermy in dinosaurs |journal=[[Nature (journal)|Nature]] |volume=238 |pages=81–85 |doi=10.1038/238081a0 |bibcode=1972Natur.238...81B|issue=5359|s2cid=4176132 }}</ref> ''Tyrannosaurus rex'' itself was claimed to have been [[Warm-blooded|endothermic]] ("warm-blooded"), implying a very active lifestyle.<ref name=bakker1986>{{Cite book |last=Bakker |first=Robert T. |author-link=Robert T. Bakker |year=1986 |title=The Dinosaur Heresies |location=New York |publisher=Kensington Publishing |isbn=978-0-688-04287-5 |oclc=13699558 |url=https://archive.org/details/dinosaurheresies00robe }}{{Page needed|date=September 2010}}</ref> Since then, several paleontologists have sought to determine the ability of ''Tyrannosaurus'' to [[thermoregulation|regulate]] its body [[temperature]]. Histological evidence of high growth rates in young ''T. rex'', comparable to those of mammals and birds, may support the hypothesis of a high metabolism. Growth curves indicate that, as in mammals and birds, ''T. rex'' growth was limited mostly to immature animals, rather than the [[indeterminate growth]] seen in most other [[vertebrate]]s.<ref name="hornerpadian2004"/> It has been indicated that the temperature difference may have been no more than 4 to 5&nbsp;°C (7 to 9&nbsp;°F) between the vertebrae of the torso and the [[tibia]] of the lower leg. This small temperature range between the body core and the extremities was claimed by paleontologist Reese Barrick and [[geochemistry|geochemist]] William Showers to indicate that ''T. rex'' maintained a constant internal body temperature ([[Warm-blooded|homeothermy]]) and that it enjoyed a metabolism somewhere between ectothermic reptiles and endothermic mammals.<ref name="barrettshowers1994">{{Cite journal|first=Reese E. |last=Barrick |author2=William J. Showers |title=Thermophysiology of Tyrannosaurus rex: Evidence from Oxygen Isotopes |journal=[[Science (journal)|Science]] |location=[[New York City]] |volume=265 |issue=5169 |pages=222–224 |date=July 1994 |pmid=17750663 |doi=10.1126/science.265.5169.222 |bibcode=1994Sci...265..222B |s2cid=39392327 }}</ref> Later they found similar results in ''[[Giganotosaurus]]'' specimens, who lived on a different continent and tens of millions of years earlier in time.<ref name="barrickshowers1999">{{Cite journal |last=Barrick |first=Reese E. |author2=William J. Showers |date=October 1999 |title=Thermophysiology and biology of ''Giganotosaurus'': comparison with ''Tyrannosaurus'' |journal=Palaeontologia Electronica |volume=2 |issue=2 |url=http://palaeo-electronica.org/1999_2/gigan/issue2_99.htm |access-date=2008-10-12 |archive-date=2011-05-17 |archive-url=https://web.archive.org/web/20110517220816/http://palaeo-electronica.org/1999_2/gigan/issue2_99.htm |url-status=live }}</ref> Even if ''Tyrannosaurus rex'' does exhibit evidence of homeothermy, it does not necessarily mean that it was endothermic. Such thermoregulation may also be explained by [[gigantothermy]], as in some living [[sea turtle]]s.<ref name="paladinoetal1997">{{Cite book|editor=[[James Farlow|James O. Farlow]] |editor2=M. K. Brett-Surman |title=The Complete Dinosaur |publisher=Indiana University Press |location=Bloomington |year=1999 |pages=491–504 |isbn=978-0-253-21313-6 |chapter=A blueprint for giants: modeling the physiology of large dinosaurs |first1=Frank V. |last1=Paladino |first2=James R. |last2=Spotila |first3=Peter |last3=Dodson}}</ref><ref name="chinsamyhillenius2004">{{Cite book|editor=David B. Weishampel |editor2=Peter Dodson |editor3=Halszka Osmólska |title=The dinosauria |publisher=University of California Press |location=Berkeley |year=2004 |pages=643–659 |isbn=978-0-520-24209-8 |chapter=Physiology of nonavian dinosaurs |first=Anusuya |last=Chinsamy |author2=Willem J. Hillenius }}</ref><ref>{{Cite journal|last=Seymour|first=Roger S.|date=2013-07-05|title=Maximal Aerobic and Anaerobic Power Generation in Large Crocodiles versus Mammals: Implications for Dinosaur Gigantothermy|journal=PLOS ONE|volume=8|issue=7|article-number=e69361|doi=10.1371/journal.pone.0069361|pmid=23861968|pmc=3702618|issn=1932-6203|bibcode=2013PLoSO...869361S|doi-access=free}}</ref>

==Paleoecology==

===Coexistence of ''Daspletosaurus'' and ''Gorgosaurus''===
[[Image:Daspletosaurus FMNH.jpg|thumb|Skeleton of ''Daspletosaurus'' (specimen FMNH PR308) at the [[Field Museum of Natural History|Field Museum]] in Chicago]]
In the Dinosaur Park Formation, ''Gorgosaurus'' lived alongside a rarer species of the tyrannosaurine ''Daspletosaurus''. This is one of the few examples of two tyrannosaur genera coexisting. Similarly sized predators in modern predator [[Guild (ecology)|guilds]] are separated into different [[ecological niche]]s by anatomical, behavioral or geographical differences that limit competition. [[Niche differentiation]] between the Dinosaur Park tyrannosaurids is not well understood.<ref name=farlowpianka2002>{{Cite journal |last=Farlow |first=James O. |author-link=James Farlow |author2=Pianka, Eric R. |year=2002 |title=Body size overlap, habitat partitioning and living space requirements of terrestrial vertebrate predators: implications for the paleoecology of large theropod dinosaurs |journal=Historical Biology |volume=16 |issue=1 |pages=21–40 |doi=10.1080/0891296031000154687 |bibcode=2002HBio...16...21F |s2cid=18114585 |url=http://doc.rero.ch/record/15105/files/PAL_E2372.pdf }}</ref> In 1970, Dale Russell [[hypothesis|hypothesized]] that the more common ''Gorgosaurus'' actively hunted fleet-footed [[Hadrosauridae|hadrosaurs]], while the rarer and more troublesome [[ceratopsia]]ns and [[ankylosauria]]ns (horned and heavily [[Armour (zoology)|armoured]] dinosaurs) were left to the more heavily built ''[[Daspletosaurus]]''.<ref name=russell1970/> However, a specimen of ''Daspletosaurus'' ([[Old Trail Museum|OTM]] 200) from the contemporaneous [[Two Medicine Formation]] of Montana preserves the digested remains of a juvenile hadrosaur in its gut region.<ref name=varricchio2001>{{Cite journal|last=Varricchio |first=David J. |year=2001 |title=Gut contents from a Cretaceous tyrannosaurid: implications for theropod dinosaur digestive tracts |journal=Journal of Paleontology |volume=75 |issue=2 |pages=401–406 |doi=10.1666/0022-3360(2001)075<0401:GCFACT>2.0.CO;2|s2cid=86113170 |issn=0022-3360|url=http://doc.rero.ch/record/14907/files/PAL_E2049.pdf }}</ref>
Unlike some other groups of dinosaurs, neither genus was more common at higher or lower elevations than the other.<ref name=farlowpianka2002/> However, ''Gorgosaurus'' appears more common in northern formations like the Dinosaur Park, with species of ''Daspletosaurus'' more abundant to the south. The same pattern is seen in other groups of dinosaurs. Chasmosaurine ceratopsians and hadrosaurine hadrosaurs are also more common in the Two Medicine Formation of Montana and in southwestern North America during the Campanian, while centrosaurines and lambeosaurines dominate in northern latitudes. Holtz has suggested that this pattern indicates shared ecological preferences between tyrannosaurines, chasmosaurines and hadrosaurines. At the end of the later Maastrichtian stage, tyrannosaurines like ''Tyrannosaurus rex'', hadrosaurines like ''[[Edmontosaurus]]'' and chasmosaurines like ''[[Triceratops]]'' were widespread throughout western North America, while albertosaurines and centrosaurines became extinct, and lambeosaurines were rare.<ref name=holtz2004/>

===Social behavior===
There is limited evidence of social behavior among the tyrannosaurids.  Researchers reported that a subadult and a juvenile skeleton were found in the same quarry as the "Sue" specimen, which has been used to support the hypothesis that tyrannosaurs may have lived in social groups of some kind.<ref name="sue">Guinness World Records Ltd. (2003). ''2003 Guinness World Records''. pg 90.</ref> While there is no evidence of gregarious behavior in ''Gorgosaurus'',<ref name=tankecurrie1998/><ref name=currieetal2005/> there is evidence of some pack behavior for ''Albertosaurus'' and ''Daspletosaurus''.

A young specimen of the Dinosaur Park ''Daspletosaurus'' species ([[Royal Tyrrell Museum of Palaeontology|TMP]] 94.143.1) shows bite marks on the face that were inflicted by another tyrannosaur. The bite marks are healed over, indicating that the animal survived the bite. A full-grown Dinosaur Park ''Daspletosaurus'' (TMP 85.62.1) also exhibits tyrannosaur bite marks, showing that attacks to the face were not limited to younger animals. While it is possible that the bites were attributable to other species, intraspecific aggression, including facial biting, is very common among predators. Facial bites are seen in other tyrannosaurs like ''Gorgosaurus'' and ''Tyrannosaurus'', as well as in other theropod genera like ''[[Sinraptor]]'' and ''[[Saurornitholestes]]''. [[Darren Tanke]] and Phil Currie hypothesize that the bites are due to [[intraspecific competition]] for territory or resources, or for dominance within a social group.<ref name=tankecurrie1998/>
[[Image:Albertosaurus.jpg|thumb|left|Full size model diorama of a group of ''Albertosaurus'', [[Royal Tyrrell Museum of Palaeontology|Royal Tyrrell Museum]]]]
Evidence that ''Daspletosaurus'' lived in social groups comes from a bonebed found in the Two Medicine Formation of Montana. The bonebed includes the remains of three ''Daspletosaurus'', including a large adult, a small juvenile, and another individual of intermediate size. At least five hadrosaurs are preserved at the same location. Geologic evidence indicates that the remains were not brought together by [[Current (stream)|river currents]] but that all of the animals were buried simultaneously at the same location. The hadrosaur remains are scattered and bear many marks from tyrannosaur teeth, indicating that the ''Daspletosaurus'' were feeding on the hadrosaurs at the time of death. The cause of death is unknown. Currie speculates that the daspletosaurs formed a [[pack hunter|pack]], although this cannot be stated with certainty.<ref name=currieetal2005/> Other scientists are skeptical of the evidence for social groups in ''Daspletosaurus'' and other large theropods;<ref name=eberthmccrea2001>{{Cite journal|last=Eberth |first=David A. |author2=McCrea, Richard T. |year=2001 |title=Were large theropods gregarious? |journal=Journal of Vertebrate Paleontology |volume=21 |issue=Supplement to Number 3 |pages=46A|doi=10.1080/02724634.2001.10010852|s2cid=220414868 }}</ref> Brian Roach and Daniel Brinkman have suggested that ''Daspletosaurus'' social interaction would have more closely resembled the modern [[Komodo dragon]], where non-cooperative individuals mob carcasses, frequently attacking and even [[cannibalism (zoology)|cannibalizing]] each other in the process.<ref name=BRDB07>{{Cite journal|last=Roach|first=Brian T.|author2=Brinkman, Daniel L. |year=2007|title=A reevaluation of cooperative pack hunting and gregariousness in ''Deinonychus antirrhopus'' and other nonavian theropod dinosaurs|journal=Bulletin of the Peabody Museum of Natural History|volume=48|issue=1|pages=103–138|doi=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2|s2cid=84175628 }}</ref>

The Dry Island bonebed discovered by Barnum Brown and his crew contains the remains of 22 ''Albertosaurus'', the most individuals found in one locality of any Cretaceous theropod, and the second-most of any large theropod dinosaur behind the ''[[Allosaurus]]'' assemblage at the [[Cleveland-Lloyd Dinosaur Quarry]] in [[Utah]]. The group seems to be composed of one very old adult; eight adults between 17 and 23 years old; seven sub-adults undergoing their rapid growth phases at between 12 and 16 years old; and six juveniles between the ages of 2 and 11 years, who had not yet reached the growth phase.<ref name=ericksonetal2006/> The near-absence of [[herbivore]] remains and the similar state of preservation between the many individuals at the ''Albertosaurus'' bonebed quarry led Phil Currie to conclude that the locality was not a predator trap like the [[La Brea Tar Pits]] in [[California]], and that all of the preserved animals died at the same time. Currie claims this as evidence of pack behavior.<ref name=currie1998>{{Cite journal |last=Currie |first=Philip J. |author-link=Phil Currie |year=1998 |title=Possible evidence of gregarious behavior in tyrannosaurids |journal=Gaia |volume=15 |pages=271–277 |url=http://www.mnhn.ul.pt/geologia/gaia/21.pdf |access-date=2008-09-13 |archive-date=2009-03-26 |archive-url=https://web.archive.org/web/20090326062833/http://www.mnhn.ul.pt/geologia/gaia/21.pdf |url-status=live }}(not printed until 2000)</ref> Other scientists are skeptical, observing that the animals may have been driven together by drought, flood or for other reasons.<ref name=ericksonetal2006/><ref name=eberthmccrea2001 /><ref name=roachbrinkman2007>{{Cite journal|last=Roach |first= Brian T. |author2=Brinkman, Daniel T. |year=2007 |title=A reevaluation of cooperative pack hunting and gregariousness in ''Deinonychus antirrhopus'' and other nonavian theropod dinosaurs |journal=Bulletin of the Peabody Museum of Natural History |volume=48 |issue=1 |pages=103–138 |doi=10.3374/0079-032X(2007)48[103:AROCPH]2.0.CO;2 |s2cid= 84175628 }}</ref>

While it generally remains controversial, evidence does exist that supports the theory that at least some tyrannosaurids were social. In [[British Columbia]]'s [[Wapiti Formation]], a [[trackway]] composed of the footprints of three individual tyrannosaurids (named as the ichnogenus ''[[Bellatoripes fredlundi]]'') was discovered by a local outfitter named Aaron Fredlund and described in the journal [[PLOS One]] by Richard McCrea et al. An examination of the trackway found no evidence of one trackway being left long after another had been made, further supporting the hypothesis that three individual tyrannosaurs were traveling together as a group. Further research revealed the animals were traveling at a speed of between {{convert|3.9|and|5.2|mph|abbr=on}} and likely had a hip height of around 7 to 9 feet. As three different genera of tyrannosaurids (''Gorgosaurus'', ''Daspletosaurus'', and ''Albertosaurus'', respectively) are known from the formation, it is unknown which genus was the maker of the trackway.<ref>{{Cite journal | doi=10.1371/journal.pone.0103613| pmid=25054328| pmc=4108409|title = A 'Terror of Tyrannosaurs': The First Trackways of Tyrannosaurids and Evidence of Gregariousness and Pathology in Tyrannosauridae| journal=PLOS ONE| volume=9| issue=7| article-number=e103613|year = 2014|last1 = McCrea|first1 = Richard T.| last2=Buckley| first2=Lisa G.| last3=Farlow| first3=James O.| last4=Lockley| first4=Martin G.| last5=Currie| first5=Philip J.| last6=Matthews| first6=Neffra A.| last7=Pemberton| first7=S. George| bibcode=2014PLoSO...9j3613M| doi-access=free}}</ref><ref>{{cite web| url=http://www.popularmechanics.com/science/environment/tyrannosaurus-trackways-reveal-a-dinosaurs-walk-17016027| title=Tyrannosaurus Tracks Show Dinosaur's Walk| date=2014-07-23| access-date=2015-01-16| archive-date=2014-09-30| archive-url=https://web.archive.org/web/20140930213639/http://www.popularmechanics.com/science/environment/tyrannosaurus-trackways-reveal-a-dinosaurs-walk-17016027| url-status=live}}</ref><ref>{{cite web| url=http://phenomena.nationalgeographic.com/2014/07/23/tracks-hint-at-the-social-life-of-tyrant-dinosaurs/| title=Tracks Hint at the Social Life of Tyrant Dinosaurs| date=2014-07-23| access-date=2015-01-16| archive-date=2015-01-08| archive-url=https://web.archive.org/web/20150108013825/http://phenomena.nationalgeographic.com/2014/07/23/tracks-hint-at-the-social-life-of-tyrant-dinosaurs/}}</ref> Additional evidence in the form of a bone-bed from the Rainbows and Unicorns Quarry in Southern Utah's Kaiparowits Formation described in 2021 attributed to ''[[Teratophoneus]]'' suggests other tyrannosaurids were also social animals. The fossils, consisting of four or possibly five different animals ranging from 4–22 years of age, suggest a mass mortality event, possibly caused by flooding, or less likely by [[cyanobacterial toxicosis]], fire, or drought. The fact that all of the animals preserved seemed to have perished within a short timespan further strengthens the argument for gregarious behavior in tyrannosaurids, with the bone beds of such genera as ''Teratophoneus'', ''Albertosaurus'', ''Tyrannosaurus'' and ''Daspletosaurus'' showcasing suggested social behavior may have been widespread amongst tyrannosauridae in general.<ref>{{Cite journal|title=Geology and taphonomy of a unique tyrannosaurid bonebed from the upper Campanian Kaiparowits Formation of southern Utah: implications for tyrannosaurid gregariousness|first1=Alan L.|last1=Titus|first2=Katja|last2=Knoll|first3=Joseph J. W.|last3=Sertich|first4=Daigo|last4=Yamamura|first5=Celina A.|last5=Suarez|first6=Ian J.|last6=Glasspool|first7=Jonathan E.|last7=Ginouves|first8=Abigail K.|last8=Lukacic|first9=Eric M.|last9=Roberts|date=April 19, 2021|journal=PeerJ|volume=9|article-number=e11013|doi=10.7717/peerj.11013|pmid=33976955|pmc=8061582|doi-access=free}}</ref><ref>{{cite news|url=https://www.washingtonpost.com/climate-environment/2021/04/19/grand-staircase-tyrannosaur/|title=Tyrannosaurs likely hunted in packs rather than heading out solo, scientists find|last=Eilperin|first=Juliet|date=April 19, 2021|newspaper=[[The Washington Post]]|archive-url=https://archive.today/20210420094932/https://www.washingtonpost.com/climate-environment/2021/04/19/grand-staircase-tyrannosaur/|archive-date=April 20, 2021|url-status=live|access-date=September 27, 2021}}</ref><ref>{{Cite web|url=https://www.telegraph.co.uk/news/science/dinosaurs/8589113/Tyrannosaurus-Rex-hunted-in-packs.html|title=Tyrannosaurus Rex 'hunted in packs'|date=22 June 2011 |access-date=2021-09-27|archive-date=2021-09-27|archive-url=https://web.archive.org/web/20210927165533/https://www.telegraph.co.uk/news/science/dinosaurs/8589113/Tyrannosaurus-Rex-hunted-in-packs.html|url-status=live}}</ref>

===Feeding===
[[Tyrannosaurus|Tyrannosaur]] tooth marks are the most commonly preserved feeding traces of carnivorous dinosaurs.<ref name="saurornitholestes" /> They have been reported from [[ceratopsia]]ns, [[Hadrosauridae|hadrosaurs]] and other tyrannosaurs.<ref name="saurornitholestes" /> [[Tyrannosaurus|Tyrannosaurid]] bones with tooth marks represent about 2% of known fossils with preserved tooth marks.<ref name="saurornitholestes">Jacobsen, A.R. 2001. Tooth-marked small theropod bone: An extremely rare trace. p. 58-63. In: Mesozoic Vertebrate Life. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.</ref> Tyrannosaurid teeth were used as holdfasts for pulling [[meat]] off a body, rather than [[knife]]-like cutting functions.<ref name="alberto-tooth">Abler, W.L. 2001. A kerf-and-drill model of tyrannosaur tooth serrations. p. 84-89. In: ''Mesozoic Vertebrate Life''. Ed.s Tanke, D. H., Carpenter, K., Skrepnick, M. W. Indiana University Press.</ref> Tooth wear patterns hint that complex head shaking behaviors may have been involved in tyrannosaur feeding.<ref name="alberto-tooth"/>
[[File:GorgosaurusDB.jpg|thumb|left|''[[Teratophoneus|Teratophoneus curriei]]'' attacking a ''[[Parasaurolophus cyrtocristatus]]'']]
Speculation on the pack-hunting habits of ''Albertosaurus'' were made by a few researchers who suggest that the younger members of the pack may have been responsible for driving their prey towards the adults, who were larger and more powerful, but also slower.<ref name=currie1998/> Juveniles may also have had different lifestyles than adults, filling predator [[Ecological niche|niches]] between those of the enormous adults and the smaller contemporaneous theropods, the largest of which were two [[Order of magnitude|orders of magnitude]] smaller than an adult ''Albertosaurus'' in mass.<ref name=holtz2004/> However, as the preservation of behavior in the fossil record is exceedingly rare, these ideas cannot readily be tested. [[Philip J. Currie|Phil Currie]] speculates that the ''Daspletosaurus'' formed [[pack hunter|packs to hunt]], although this cannot be stated with certainty.<ref name=currieetal2005/> There is no evidence of such gregarious behavior in ''Gorgosaurus''.<ref name=tankecurrie1998>{{Cite journal |last=Tanke |first=Darren H. |author2=Currie, Philip J. |author-link2=Philip J. Currie |year=1998 |title=Head-biting behavior in theropod dinosaurs: paleopathological evidence |journal=Gaia |volume=15 |pages=167–184 |url=http://www.mnhn.ul.pt/geologia/gaia/12.pdf |access-date=2008-09-13 |archive-date=2008-02-27 |archive-url=https://web.archive.org/web/20080227134632/http://www.mnhn.ul.pt/geologia/gaia/12.pdf |url-status=live }} [not printed until 2000]</ref><ref name=currieetal2005>{{Cite book|last1=Currie |first1=Philip J. |author-link=Phil Currie |last2=Trexler |first2=David |author-link3=Eva Koppelhus|last3=Koppelhus |first3=Eva B. |last4=Wicks |first4=Kelly |last5=Murphy |first5=Nate |year=2005 |chapter=An unusual multi-individual tyrannosaurid bonebed in the Two Medicine Formation (Late Cretaceous, Campanian) of Montana (USA) |editor=[[Kenneth Carpenter|Carpenter, Kenneth]] |title=The Carnivorous Dinosaurs |publisher=Indiana University Press |location=Bloomington |pages=313–324 |isbn=978-0-253-34539-4}}</ref>

The debate about whether ''Tyrannosaurus'' was a [[predation|predator]] or a pure [[scavenger]] is as old as the debate about its locomotion. Lambe (1917) described a good skeleton of ''Tyrannosaurus''{{'}}s close relative ''Gorgosaurus'' and concluded that it and therefore also ''Tyrannosaurus'' was a pure scavenger, because the ''Gorgosaurus''{{'}}s teeth showed hardly any wear.<ref name="Lambe1917Gorgosaurus">{{Cite journal|author=Lambe, L. B.|year=1917|title=The Cretaceous theropodous dinosaur ''Gorgosaurus''|journal=Memoirs of the Geological Survey of Canada|volume=100|pages=1–84|doi=10.4095/101672|url=https://www.biodiversitylibrary.org/item/252624|access-date=2021-09-23|archive-date=2021-09-09|archive-url=https://web.archive.org/web/20210909121735/https://www.biodiversitylibrary.org/item/252624|url-status=live}}</ref> This argument is no longer taken seriously, because theropods replaced their teeth quite rapidly. Ever since the first discovery of ''Tyrannosaurus'' most scientists have agreed that it was a predator, although like modern large predators it would have been happy to scavenge or steal another predator's kill if it had the opportunity.<ref name="FarlowHoltz2002FossilRecordPredation">{{Cite web|editor=Kowalewski, M.|editor2=Kelley, P.H|title=The Fossil Record of Predation|year=2002|series=The Paleontological Society Papers|volume=8|pages=251–266|url=http://www.yale.edu/ypmip/predation/Chapter_09.pdf|author1=Farlow, J. O.|author2=Holtz, T. R.|archive-url=https://web.archive.org/web/20081031093048/http://www.yale.edu/ypmip/predation/Chapter_09.pdf|archive-date=2008-10-31}}</ref><ref name="dinocards2">Dorey, M. (1997). Tyrannosaurus. ''Dinosaur Cards''. Orbis Publishing Ltd. D36045907.</ref>

Noted [[Hadrosaurid|hadrosaur]] expert [[Jack Horner (paleontologist)|Jack Horner]] is currently the major advocate of the idea that ''Tyrannosaurus'' was exclusively a scavenger and did not engage in active hunting at all.<ref name="hornerlessem1993" /><ref name="Horner1994SteakKnives">{{Cite journal|author=Horner, J.R.|year=1994|title=Steak knives, beady eyes, and tiny little arms (a portrait of ''Tyrannosaurus'' as a scavenger)|journal=The Paleontological Society Special Publication|volume=7|pages=157–164|doi=10.1017/S2475262200009497}}</ref><ref name="BBC2003TrexOnTrial">{{Cite news|url=https://news.bbc.co.uk/2/hi/science/nature/3112527.stm|title=T. rex goes on trial|author=Amos, J.|publisher=BBC|date=31 July 2003|access-date=12 October 2008|archive-date=13 March 2012|archive-url=https://web.archive.org/web/20120313130020/http://news.bbc.co.uk/1/hi/sci/tech/3112527.stm|url-status=live}}</ref> Horner has presented several arguments to support the pure scavenger hypothesis. The presence of large [[olfactory bulb]]s and [[olfactory nerve]]s suggests a highly developed sense of smell for sniffing out carcasses over great distances. The teeth could crush bone, and therefore could extract as much food ([[bone marrow]]) as possible from carcass remnants, usually the least nutritious parts. At least some of its potential prey could move quickly, while evidence suggests that Tyrannosaurus walked instead of ran.<ref name="Horner1994SteakKnives" /><ref name="dinodictionary"/>

Other evidence suggests hunting behavior in ''Tyrannosaurus''. The eye-sockets of tyrannosaurs are positioned so that the eyes would point forward, giving them [[binocular vision]] slightly better than that of modern [[hawk]]s. Tyrannosaur-inflicted damage has been found on skeletons of hadrosaurs and ''[[Triceratops]]'' that seemed to have survived initial attacks.<ref name="erickson1996">{{cite journal | author1 = Erickson G. M. | author2 = Olson K. H. | year = 1996 | title = Bite marks attributable to ''Tyrannosaurus rex'': preliminary description and implications | url = https://zenodo.org/record/3732430 | journal = Journal of Vertebrate Paleontology | volume = 16 | issue = 1 | pages = 175–178 | doi = 10.1080/02724634.1996.10011297 | bibcode = 1996JVPal..16..175E | access-date = 2020-09-12 | archive-date = 2021-10-19 | archive-url = https://web.archive.org/web/20211019153802/https://zenodo.org/record/3732430 | url-status = live }}</ref><ref name=carpenter1998>{{Cite journal|last=Carpenter |first=K. |author-link=Kenneth Carpenter |year=1998 |title=Evidence of predatory behavior by theropod dinosaurs |journal=Gaia |volume=15 |pages=135–144 |url=http://vertpaleo.org/publications/jvp/15-576-591.cfm|access-date=5 December 2007 |archive-url=https://web.archive.org/web/20071117132451/http://vertpaleo.org/publications/jvp/15-576-591.cfm <!--Added by H3llBot--> |archive-date=17 November 2007}}</ref><ref name="fowler2006">{{Cite journal|first=Denver W. |last= Fowler |author2=Robert M. Sullivan |year=2006 |title=A ceratopsid pelvis with toothmarks from the Upper Cretaceous Kirtland Formation, New Mexico: evidence of late Campanian tyrannosaurid feeding behavior |journal=New Mexico Museum of Natural History and Science Bulletin |volume=35 |pages=127–130}}</ref> Some researchers argue that if ''Tyrannosaurus'' were a scavenger, another dinosaur had to be the top predator in the Amerasian Upper Cretaceous. The top prey were the larger [[marginocephalia]]ns and [[ornithopod]]s. The other tyrannosaurids share so many characteristics with ''Tyrannosaurus'' that only small [[Dromaeosauridae|dromaeosaurs]] remain as feasible top predators. In this light, scavenger hypothesis adherents have suggested that the size and power of tyrannosaurs allowed them to [[kleptoparasitism|steal kills]] from smaller predators.<ref name="dinodictionary">Walters, M., Paker, J. (1995). Dictionary of Prehistoric Life. Claremont Books. {{ISBN|1-85471-648-4}}.</ref>

[[File:Gorgosaurus TMP 2009.12.14.jpg|thumb|''Gorgosaurus'' juvenile specimen TMP 2009.12.14, featuring stomach contents comprising remains of ''[[Citipes]]'']]
In 2023, a juvenile ''Gorgosaurus'' with its ''[[in situ]]'' stomach contents containing two ''[[Citipes]]'' juveniles about a year old intact has been reported from the [[Dinosaur Park Formation]]. This juvenile would have been 5–7 years old at the time of death, measuring about {{convert|4|m|ft}} long and weighing around {{convert|335|kg|lb}}. It is much larger than the two ''Citipes'' juveniles that weigh about {{convert|9|-|12|kg}}, contrary to the assumption that tyrannosaurids fed on prey of their size once they reached {{convert|16|-|32|kg|lb}}, indicating that juvenile tyrannosaurids still consumed much smaller prey after exceeding a certain size threshold. The discovery of this specimen indicated that tyrannosaurids probably did not hunt in multigenerational packs, since its prey size is too small to share with the conspecifics. It is also a direct dietary evidence that reinforces the theory of 'ontogenetic dietary shift' for tyrannosaurids, as previously inferred by ecological modeling and anatomical features among different age groups. Only the remains of the hindlimbs and caudal vertebrae of juvenile ''Citipes'' were present in the tyrannosaurid's stomach cavity, suggesting that a juvenile ''Gorgosaurus'' may have had preferential consumption of the muscular hindlimbs.<ref>{{Cite journal|last1=Therrien |first1=F. |last2=Zelenitsky |first2=D. K. |last3=Tanaka |first3=K. |last4=Voris |first4=J. T. |last5=Erickson |first5=G. M. |last6=Currie |first6=P. J. |last7=DeBuhr |first7=C. L. |last8=Kobayashi |first8=Y. |title=Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator |year=2023 |journal=Science Advances |volume=9 |issue=49 |article-number=eadi0505 |doi=10.1126/sciadv.adi0505 |doi-access=free |pmid=38064561 |bibcode=2023SciA....9I.505T |pmc=10846869 }}</ref>

====Cannibalism==== 
Evidence also strongly suggests that tyrannosaurids were at least occasionally cannibalistic. ''Tyrannosaurus'' itself has strong evidence pointing towards it having been cannibalistic in at least a scavenging capacity based on tooth marks on the foot bones, humerus, and metatarsals of one specimen.<ref name="HornerCurrie_et.al._2010_Trex_cannibalism">{{Cite journal |last1=Longrich |first1=N. R. |last2=Horner |first2=J. R. |last3=Erickson |first3=G. M. |last4=Currie |first4=P. J. |year=2010 |title=Cannibalism in ''Tyrannosaurus rex'' |journal=PLOS ONE |volume=5 |issue=10 |article-number=e13419 |doi=10.1371/journal.pone.0013419 |pmc=2955550 |pmid=20976177|bibcode=2010PLoSO...513419L |doi-access=free }}</ref> Fossils from the [[Fruitland Formation]], [[Kirtland Formation]] (both Campanian in age), and Maastichtian-aged [[Ojo Alamo Formation]] suggest that cannibalism was present in various tyrannosaurid genera of the San Juan Basin. The evidence gathered from the specimens suggests opportunistic feeding behavior in tyrannosaurids that cannibalized members of their own species.<ref>{{Cite web|url=https://www.researchgate.net/publication/348002335|title=NEW EVIDENCE FOR CANNIBALISM IN TYRANNOSAURID DINOSAURS FROM THE UPPER CRETACEOUS (CAMPANIAN/MAASTRICHTIAN) SAN JUAN BASIN OF NEW MEXICO|website=ResearchGate|access-date=2021-01-06|archive-date=2021-11-10|archive-url=https://web.archive.org/web/20211110091047/https://www.researchgate.net/publication/348002335_NEW_EVIDENCE_FOR_CANNIBALISM_IN_TYRANNOSAURID_DINOSAURS_FROM_THE_UPPER_CRETACEOUS_CAMPANIANMAASTRICHTIAN_SAN_JUAN_BASIN_OF_NEW_MEXICO|url-status=live}}</ref>

===Distribution===
[[Image:Tyrannosauroid fossil localities map.png|thumb|right|450px|While earlier tyrannosauroids are found on all three northern continents, with possible remains from Australia, tyrannosaurid fossils (blue dots) are known only from North America and Asia]]The earliest known tyranosaur remains occurred between 129.4 and 125 million years ago in Ishikawa, Japan near Lat 36.166668	lng 136.633331. Found by [https://paleobiodb.org/classic/displayCollResults?a=basicCollectionSearch&collection_no=32324 Marsh in 1881] and identified by H.F. Osborne in 1906, the age of the remains was determined by H. Matsuoka et al. in 2002. 
While earlier tyrannosauroids are found on all three northern continents, tyrannosaurid fossils are known only from North America and Asia. Sometimes fragmentary remains uncovered in the Southern Hemisphere have been reported as "Southern Hemisphere tyrannosaurids," although these seem to have been misidentified [[Abelisauridae|abelisaurid]] fossils.<ref name="ageofdinosaursabelisaurus">{{Cite book|chapter=Abelisaurus|author1=Dodson, Peter |author2=Britt, Brooks |author3=Carpenter, Kenneth |author4=Forster, Catherine A. |author5=Gillette, David D. |author6=Norell, Mark A. |author7=Olshevsky, George |author8=Parrish, J. Michael |author9= Weishampel, David B.  |name-list-style=amp |title=Age of Dinosaurs|publisher=Publications International, LTD|page=105|isbn=978-0-7853-0443-2|year=1993}}</ref> 

Tyrannosaurid remains have never been recovered from eastern North America, while more basal tyrannosauroids, like ''[[Dryptosaurus]]'' and ''[[Appalachiosaurus]]'', persisted there until the end of the Cretaceous, indicating that tyrannosaurids must have evolved in or [[biological dispersal|dispersed]] into western North America after the continent was divided in half by the [[Western Interior Seaway]] in the middle of the Cretaceous.<ref name=carretal2005/> Tyrannosaurid fossils have been found in [[Alaska]], which may have provided a route for dispersal between North America and Asia.<ref name=fiorillogangloff2000>{{Cite journal|last=Fiorillo |first=Anthony R. |author2=Gangloff, Roland A. |year=2000 |title=Theropod teeth from the Prince Creek Formation (Cretaceous) of northern Alaska, with speculations on arctic dinosaur paleoecology |journal=Journal of Vertebrate Paleontology |volume=20 |issue=4 |pages=675–682 |doi=10.1671/0272-4634(2000)020[0675:TTFTPC]2.0.CO;2|s2cid=130766946 |issn=0272-4634}}</ref> ''Alioramus'' and ''Tarbosaurus'' are found to be related in one cladistic analysis, forming a unique Asian branch of the family.<ref name=currieetal2003/> This was later disproven with the discovery of ''[[Qianzhousaurus]]'' and the description of the tyrannosaur family Alioramini. Tyrannosaurid teeth from a large species of unknown variety were discovered in the Nagasaki Peninsula by researchers from the Fukui Prefectural Dinosaur Museum, further expanding the range of the group. The teeth were estimated to be 81&nbsp;million years old ([[Campanian]] Age).<ref>{{Cite web |url=http://www.irishexaminer.com/examviral/science-world/these-81-million-year-old-teeth-are-the-first-bit-of-evidence-of-japans-largest-ever-dinosaur-342857.html |title=These 81-million-year-old teeth are the first bit of evidence of Japan's largest ever dinosaur &#124; Irish Examiner |date=16 July 2015 |access-date=2016-03-10 |archive-date=2016-04-12 |archive-url=https://web.archive.org/web/20160412104057/http://www.irishexaminer.com/examviral/science-world/these-81-million-year-old-teeth-are-the-first-bit-of-evidence-of-japans-largest-ever-dinosaur-342857.html |url-status=live }}</ref>
[[Image:TarbosaurusP1050352.jpg|thumb|left|Skeleton cast of ''Tarbosaurus bataar'', a tyrannosaurid from Asia]]
Of the two subfamilies, tyrannosaurines appear to have been more widespread. Albertosaurines are unknown in Asia, which was home to the tyrannosaurines, such as ''Tarbosaurus'' and ''Zhuchengtyrannus'', and ''Qianzhousaurus'' and ''Alioramus'' of the [[#Taxonomy|Alioramini]]. Both the Tyrannosaurinae and Albertosaurinae subfamilies were present in the Campanian and early [[Maastrichtian]] stages of North America, with tyrannosaurines like ''Daspletosaurus'' ranging throughout the Western Interior, while the albertosaurines ''Albertosaurus'' and ''Gorgosaurus'' are currently known only from the northwestern part of the continent.<ref>{{Cite journal|title=The Phylogenetic Position of the Tyrannosauridae: Implications for Theropod Systematics|author=Thomas R. Holtz Jr.|journal=Journal of Paleontology|volume=68|issue=5|year=1994|pages=1100–1117|jstor=1306180|doi=10.1017/S0022336000026706|bibcode=1994JPal...68.1100H |s2cid=129684676 }}</ref>

By the late Maastrichtian, albertosaurines appear to have gone extinct, while the tyrannosaurine ''Tyrannosaurus'' roamed from [[Saskatchewan]] to [[Texas]]. This pattern is mirrored in other North American dinosaur taxa. During the Campanian and early Maastrichtian, [[Hadrosaurid|lambeosaurine]] [[Hadrosauridae|hadrosaurs]] and [[centrosaurinae|centrosaurine]] [[ceratopsia]]ns are common in the northwest, while [[Hadrosauridae|hadrosaurines]] and [[Ceratopsidae|chasmosaurines]] were more common to the south. By the end of the Cretaceous, centrosaurines are unknown and lambeosaurines are rare, while hadrosaurines and chasmosaurines were common throughout the Western Interior.<ref name=holtz2004/> A study published in the journal ''Scientific Reports'' on February 2, 2016, by Steve Brusatte, Thomas Carr ''et al''. indicates that during the later Maastrichtian, ''Tyrannosaurus'' itself might have been partially responsible for the extinction of the other tyrannosaurids in most of western North America. The study indicates that ''Tyrannosaurus'' might have been an immigrant from Asia as opposed to having evolved in North America (possibly a descendant of the closely related ''Tarbosaurus'') that supplanted and outcompeted other tyrannosaurids. This theory is further supported by the fact that few to no other types of tyrannosaurid are found within ''Tyrannosaurus''' known range.<ref>{{Cite web|url=https://www.livescience.com/53877-t-rex-was-invasive-species.html|title=T. Rex Was Likely an Invasive Species|first=Laura Geggel 29|last=February 2016|website=livescience.com|date=29 February 2016|access-date=5 January 2021|archive-date=14 July 2019|archive-url=https://web.archive.org/web/20190714170020/https://www.livescience.com/53877-t-rex-was-invasive-species.html|url-status=live}}</ref>

==Timeline of genera==

<timeline>
ImageSize  = width:800px height:auto barincrement:15px
PlotArea   = left:10px bottom:50px top:10px right:10px

Period      = from:-100.5 till:-60
TimeAxis    = orientation:horizontal
ScaleMajor  = unit:year increment:10 start:-100
ScaleMinor  = unit:year increment:1 start:-100
TimeAxis    = orientation:hor
AlignBars   = justify

Colors =
 #legends
  id:CAR   value:claret
  id:ANK   value:rgb(0.4,0.3,0.196)
  id:HER   value:teal
  id:HAD   value:green
  id:OMN   value:blue
  id:black        value:black
  id:white        value:white
  id:latecretaceous   value:rgb(0.74,0.82,0.37)

BarData=
 bar:eratop
 bar:space
 bar:periodtop
 bar:space
 bar:NAM1
 bar:NAM2
 bar:NAM3
 bar:NAM4
 bar:NAM5
 bar:NAM6
 bar:NAM7
 bar:NAM8
 bar:NAM9
 bar:NAM10
 bar:NAM11
 bar:NAM12
 bar:NAM13
 bar:NAM14

 bar:space
 bar:period
 bar:space
 bar:era

PlotData=
 align:center textcolor:black fontsize:M mark:(line,black) width:25
 shift:(7,-4)

 bar:periodtop
 from: -100.5   till: -93.9    color:latecretaceous    text:[[Cenomanian]]
 from: -93.9    till: -89.8    color:latecretaceous    text:[[Turonian]]
 from: -89.8    till: -86.3    color:latecretaceous    text:[[Coniacian|Coniac.]]
 from: -86.3    till: -83.6    color:latecretaceous    text:[[Santonian|Sant.]]
 from: -83.6    till: -72.1    color:latecretaceous    text:[[Campanian]]
 from: -72.1    till: -66      color:latecretaceous    text:[[Maastrichtian]]

 bar:eratop
 from: -100.5    till: -66     color:latecretaceous    text:[[Late Cretaceous]]

PlotData=
 align:left fontsize:M mark:(line,white) width:5 anchor:till align:left

 color:ANK bar:NAM1   from:-80.6   till:-79.9 text:[[Lythronax]]
 color:ANK bar:NAM2   from:-78.5   till:-78.0 text:[[Dynamoterror]]
 color:ANK bar:NAM3   from:-77    till:-76 text:[[Teratophoneus]]
 color:ANK bar:NAM4   from:-77    till:-74 text:[[Daspletosaurus]]
 color:OMN bar:NAM5   from:-76.6    till:-75.1 text:[[Gorgosaurus]]
 color:ANK bar:NAM6   from:-74.84   till:-74.26 text:[[Bistahieversor]]
 color:ANK bar:NAM7   from:-73.6    till:-73.4 text:[[Zhuchengtyrannus]]
 color:OMN bar:NAM8   from:-71    till:-68 text:[[Albertosaurus]]
 color:ANK bar:NAM9   from:-70.1    till:-69.9 text:[[Alioramus]]
 color:ANK bar:NAM10   from:-70.1    till:-69.9 text:[[Tarbosaurus]]
 color:ANK bar:NAM11   from:-69.1    till:-69.2 text:[[Nanuqsaurus]]
 color:ANK bar:NAM12   from:-67    till:-66.7 text:[[Asiatyrannus]]
 color:ANK bar:NAM13   from:-67    till:-66 text:[[Qianzhousaurus]]
 color:ANK bar:NAM14   from:-68    till:-66 text:[[Tyrannosaurus]]

PlotData=
 align:center textcolor:black fontsize:M mark:(line,black) width:25

 bar:period
 from: -100.5    till: -93.9    color:latecretaceous    text:[[Cenomanian]]
 from: -93.9    till: -89.8    color:latecretaceous    text:[[Turonian]]
 from: -89.8    till: -86.3    color:latecretaceous    text:[[Coniacian|Coniac.]]
 from: -86.3    till: -83.6    color:latecretaceous    text:[[Santonian|Sant.]]
 from: -83.6    till: -72.1    color:latecretaceous    text:[[Campanian]]
 from: -72.1    till: -66    color:latecretaceous    text:[[Maastrichtian]]

 bar:era
 from: -100.5    till: -66    color:latecretaceous    text:[[Late Cretaceous]]

</timeline>

==See also==
* [[Timeline of tyrannosaur research]]

{{Clear}}

==References==
{{Reflist}}
<ref name="The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures">{{cite journal |last1=Hieronymus |first1=Tobin |last2=Witmer |first2=Lawrence |last3=Tanke |first3=Darren |last4=Currie |first4=Philip |title=The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures |journal=The Anatomical Record |date=August 26, 2009 |volume=292 |issue=9 |pages=1370–1396 |doi=10.1002/ar.20985
|pmid=19711467 |doi-access=free }}</ref>

==External links==
{{Wikispecies|Tyrannosauridae}}
{{Commons category|Tyrannosauridae}}
* [https://web.archive.org/web/20130929074932/http://archosaur.us/theropoddatabase/Tyrannosauroidea.html#Tyrannosauridae Tyrannosauridae] specimen list and discussion at The Theropod Database

{{Theropoda|C.}}
{{Taxonbar|from=Q131050}}
{{Authority control}}

[[Category:Tyrannosauridae| ]]
[[Category:Dinosaur families]]
[[Category:Late Cretaceous dinosaurs]]