{{Short description|Extinct superfamily of dinosaurs}} {{Redirect|Tyrannosaur|the film|Tyrannosaur (film)|the rifle cartridge|.577 Tyrannosaur}} {{Good article}} {{Automatic taxobox | taxon = Tyrannosauroidea | name = | fossil_range = <br/>Middle Jurassic–Late Cretaceous, {{fossilrange|166|66}}{{Period fossil range|Jurassic-Cretaceous|166|66}}Possible extended range if ''Iliosuchus'' is a tyrannosauroid. | image = Tyrannosauroidea Infobox Panoply.png | image_upright = 1.3 | image_caption = Six tyrannosauroids (top left to bottom right): ''Tyrannosaurus'', ''Dilong'', ''Alioramus'' (background) with ''Guanlong'' (foreground), ''Gorgosaurus'', and a pair of ''Yutyrannus'' | display_parents = 2 | authority = Osborn, 1906 (vide Walker, 1964) | type_genus = {{extinct}}''Tyrannosaurus'' | type_genus_authority = Osborn, 1905 | subdivision_ranks = Subgroups | subdivision = *{{extinct}}'''Proceratosauridae''' *{{extinct}}'''Pantyrannosauria''' <small>Delcourt & Grillo, 2018</small> **{{extinct}}''Alectrosaurus'' **{{extinct}}''Chingkankousaurus'' **{{extinct}}''Dilong'' **{{extinct}}''Eotyrannus'' **{{extinct}}''Jinbeisaurus''? **{{extinct}}''Juratyrant'' **{{extinct}}''Khankhuuluu'' **{{extinct}}''Moros'' **{{extinct}}''Stokesosaurus'' **{{extinct}}''Suskityrannus'' **{{extinct}}''Timurlengia'' **{{extinct}}''Xiongguanlong'' **{{extinct}}''Yutyrannus''? **{{extinct}}'''Eutyrannosauria''' <small>Delcourt & Grillo, 2018</small> ***{{extinct}}''Appalachiosaurus'' ***{{extinct}}''Bagaraatan'' <small>(possible chimera)</small> ***{{extinct}}''Bistahieversor''? ***{{extinct}}''Dryptosaurus'' ***{{extinct}}''Nanotyrannus'' ***{{extinct}}''Raptorex'' ***{{extinct}}''Stygivenator'' ***{{extinct}}'''Tyrannosauridae''' {{Collapse top|title=Possible tyrannosauroids |left=yes|padding=0|border=0|border2=0|bg=clear|bg2=clear}} *{{extinct}}''Aniksosaurus'' *{{extinct}}''Aviatyrannis'' *{{extinct}}''Coelurus'' *{{extinct}}''Gualicho'' *{{extinct}}''Iliosuchus'' *{{extinct}}''Labocania'' *{{extinct}}''Santanaraptor'' *{{extinct}}''Shaochilong'' *{{extinct}}''Siamotyrannus'' *{{extinct}}''Siats'' *{{extinct}}''Tanycolagreus'' *{{extinct}}''Timimus'' *{{extinct}}'''Megaraptora''' {{Collapse bottom}} }} '''Tyrannosauroidea''' (meaning 'tyrant lizard forms') is a superfamily (or clade) of coelurosaurian theropod dinosaurs that includes the family Tyrannosauridae as well as more basal relatives. Tyrannosauroids lived on the Laurasian supercontinent beginning in the Jurassic Period. By the end of the Cretaceous Period, tyrannosauroids were the dominant large predators in the Northern Hemisphere, culminating in the gigantic ''Tyrannosaurus''. Fossils of tyrannosauroids have been recovered on what are now the continents of North America, Europe and Asia. If Megaraptora is part of Tyrannosauroidea, this would extend the distribution of the group to Australia and South America, and possible fragmentary remains of tyrannosauroids have also been reported from these continents.
Tyrannosauroids were bipedal carnivores, as were most theropods, and were characterized by numerous skeletal features, especially of the skull and pelvis. Early in their existence, tyrannosauroids were small predators with long, three-fingered forelimbs. Late Cretaceous genera became much larger, including some of the largest land-based predators ever to exist, but most of these later genera had proportionately small forelimbs with only two digits. Primitive feathers have been identified in fossils of two species and may have been present in other tyrannosauroids as well. Prominent bony crests in a variety of shapes and sizes on the skulls of many tyrannosauroids may have served display functions.
==Description== thumb|left|Size of some small genera, compared to a human. Tyrannosauroids varied widely in size, although there was a general trend towards increasing size over time. Early tyrannosauroids were small animals.<ref name=holtz2004>{{cite book |last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |year=2004 |chapter=Tyrannosauroidea |editor= Weishampel, David B. |editor2=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> One specimen of ''Dilong'', almost fully grown, measured {{convert|1.6|m|ft|abbr=off|sp=us}} in length,<ref name=xuetal2004>{{cite journal |last1= Xu Xing |author2= Norell, Mark A.; Kuang Xuewen; Wang Xiaolin; Zhao Qi; & 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|author-link= Xu Xing (paleontologist) |bibcode= 2004Natur.431..680X |last3= Kuang |first3= Xuewen |last4= Wang |first4= Xiaolin |last5= Zhao |first5= Qi |last6= Jia |first6= Chengkai |s2cid= 4381777 |url= http://doc.rero.ch/record/15283/files/PAL_E2582.pdf }}</ref> and a fully grown ''Guanlong'' measured {{convert|3|m|ft|abbr=off|sp=us}} long.<ref name=xuetal2006>{{cite journal |last1=Xu Xing |author2=Clark, James M.; Forster, Catherine A.; Norell, Mark A.; Erickson, Gregory M.; Eberth, David A.; Jia Chengkai; & Zhao Qi. |year=2006 |title=A basal tyrannosauroid dinosaur from the Late Jurassic of China |journal=Nature |volume=439 |issue=7077 |pages=715–718 |doi=10.1038/nature04511 |pmid=16467836 |first1=X|author-link=Xu Xing (paleontologist) |bibcode=2006Natur.439..715X |last3=Forster |first3=Catherine A. |last4=Norell |first4=Mark A. |last5=Erickson |first5=Gregory M. |last6=Eberth |first6=David A. |last7=Jia |first7=Chengkai |last8=Zhao |first8=Qi |s2cid=4424849 }}</ref> Teeth from Lower Cretaceous rocks (140 to 136 million years old) of Hyogo, Japan, appear to have come from an approximately {{convert|5|m|ft}} long animal, possibly indicating an early size increase in the lineage.<ref name="jptimes">{{cite news|url=http://www.japantimes.co.jp/news/2009/06/21/national/tyrannosaurus-ancestors-teeth-found-in-hyogo/|title=Tyrannosaurus ancestor's teeth found in Hyogo|date=2009-06-21|newspaper=The Japan Times|access-date=2014-06-28|archive-date=2014-07-14|archive-url=https://web.archive.org/web/20140714173232/http://www.japantimes.co.jp/news/2009/06/21/national/tyrannosaurus-ancestors-teeth-found-in-hyogo/}}</ref> An immature ''Eotyrannus'' was over {{convert|4|m|ft|abbr=off|sp=us}} in length,<ref name=huttetal2001>{{cite journal |last=Hutt |first=Stephen |author2=Naish, Darren |year=2001 |title=A preliminary account of a new tyrannosauroid theropod from the Wessex Formation (Early Cretaceous) of southern England |journal=Cretaceous Research |volume=22 |issue=2 |pages=227–242 |doi=10.1006/cres.2001.0252 |bibcode=2001CrRes..22..227H |s2cid=16881410 |url=http://doc.rero.ch/record/14510/files/PAL_E1710.pdf |author-link2=Darren Naish |archive-date=2023-03-02 |access-date=2023-11-30 |archive-url=https://web.archive.org/web/20230302221439/https://doc.rero.ch/record/14510/files/PAL_E1710.pdf |url-status=live }}</ref> and a subadult ''Appalachiosaurus'' was estimated at more than {{convert|6|m|ft|abbr=off|sp=us}} long,<ref name=holtz2004/> indicating that both genera reached larger sizes. The Late Cretaceous tyrannosaurids ranged from the {{convert|9|m|ft|abbr=off|sp=us}} ''Albertosaurus'' and ''Gorgosaurus'' to ''Tyrannosaurus'', which exceeded {{convert|12|m|ft|abbr=off|sp=us}} in length and may have weighed more than 6,400 kilograms (7 short tons).<ref name=holtz2004/> A 2010 review of the literature concluded that tyrannosaurs were "small- to mid-sized" for their first 80 million years but were "some of the largest terrestrial carnivores to ever live" in their last 20 million years.<ref name=BrusatteEtAl2010>{{Cite journal| author = Brusatte, S.L.| title = Tyrannosaur paleobiology: new research on ancient exemplar organisms| journal = Science| volume = 329| issue = 5998| pages = 1481–1485| year = 2010| pmid = 20847260| doi = 10.1126/science.1193304| bibcode = 2010Sci...329.1481B| author-link = Stephen L. Brusatte| last2 = Norell| first2 = Mark A.| last3 = Carr| first3 = Thomas D.| last4 = Erickson| first4 = Gregory M.| last5 = Hutchinson| first5 = John R.| last6 = Balanoff| first6 = Amy M.| last7 = Bever| first7 = Gabe S.| last8 = Choiniere| first8 = Jonah N.| last9 = Makovicky| first9 = Peter J.| last10 = Xu| first10 = Xing| s2cid = 45978858| url = https://www.pure.ed.ac.uk/ws/files/8236796/PDF_Brusatteetal2010TyrannosaurPaleobiology.pdf| hdl = 20.500.11820/fc52fb23-10e8-466d-a7e9-081260d166c6| hdl-access = free| archive-date = 2021-04-01| access-date = 2018-08-06| archive-url = https://web.archive.org/web/20210401191028/https://www.pure.ed.ac.uk/ws/files/8236796/PDF_Brusatteetal2010TyrannosaurPaleobiology.pdf| url-status = live}}</ref><ref>{{cite news |title=Tyrannosaurs were human-size for 80 million years |author= Handwerk, B. |newspaper= National Geographic News |date= 16 September 2010 |url=http://news.nationalgeographic.com/news/2010/09/100916-tyrannosaurs-t-rex-human-size-science-dinosaurs/ |archive-url=https://web.archive.org/web/20100918133037/http://news.nationalgeographic.com/news/2010/09/100916-tyrannosaurs-t-rex-human-size-science-dinosaurs/ |archive-date=September 18, 2010 |access-date=17 September 2010 }}</ref>
[[File:Daspletosaurus FMNH.jpg|thumb|left|Skull and neck of ''Daspletosaurus'', from the Field Museum of Natural History in Chicago.]] Skulls of early tyrannosauroids were long, low and lightly constructed, similar to other coelurosaurs, while later forms had taller and more massive skulls. Despite the differences in form, certain skull features are found in all known tyrannosauroids. The premaxillary bone is very tall, blunting the front of the snout, a feature which evolved convergently in abelisaurids. The nasal bones are characteristically fused, arched slightly upwards and often very roughly textured on their upper surface. The premaxillary teeth at the front of the upper jaw are shaped differently from the rest of the teeth, smaller in size and with a ''D''-shaped cross section. In the lower jaw, a prominent ridge on the surangular bone extends sideways from just below the jaw joint, except in the basal ''Guanlong''.<ref name=holtz2004/><ref name=xuetal2004/><ref name=xuetal2006/>
Tyrannosauroids had ''S''-shaped necks and long tails, as did most other theropods. Early genera had long forelimbs, about 60% the length of the hindlimb in ''Guanlong'', with the typical three digits of coelurosaurs.<ref name=xuetal2006/> The long forelimb persisted at least through the Early Cretaceous ''Eotyrannus'',<ref name=huttetal2001/> but is unknown in ''Appalachiosaurus''.<ref name=carretal2005>{{cite journal |last=Carr |first=Thomas D. |author2=Williamson, Thomas E.; & 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 }}</ref> Derived tyrannosaurids have forelimbs strongly reduced in size, the most extreme example being ''Tarbosaurus'' from Mongolia, where the humerus was only one-quarter the length of the femur.<ref name=holtz2004/> The third digit of the forelimb was also reduced over time. This digit was unreduced in the basal ''Guanlong'',<ref name=xuetal2006/> while in ''Dilong'' it was more slender than the other two digits.<ref name=xuetal2004/> ''Eotyrannus'' also had three functional digits on each hand.<ref name=huttetal2001/> Tyrannosaurids had only two, although the vestigial metacarpal of the third are preserved in some well-preserved specimens.<ref name=quinlanetal2007>{{cite journal |last=Quinlan |first=Elizibeth D. |author2=Derstler, Kraig; & Miller, Mercedes M. |year=2007 |title=Anatomy and function of digit III of the ''Tyrannosaurus rex'' manus |journal=Geological Society of America Annual Meeting — Abstracts with Programs |page=77 |url=http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm |access-date=2007-12-15 |archive-date=2008-02-24 |archive-url=https://web.archive.org/web/20080224015023/http://gsa.confex.com/gsa/2007AM/finalprogram/abstract_132345.htm }} [abstract only]</ref> As in most coelurosaurs, the second digit of the hand is the largest, even when the third digit is not present. The radius in tyrannosauroids the radius is distally flattened, just like members of Maniraptora but unlike the condition seen in ornithomimosaurs and alvarezsaurids.<ref>{{Cite journal|title=A basal tyrannosauroid dinosaur from the Late Jurassic of China|url=https://www.nature.com/articles/nature04511|journal=Nature|date=February 2006|issn=1476-4687|pages=715–718|volume=439|issue=7077|doi=10.1038/nature04511|language=en|first=Xing|last=Xu|first2=James M.|last2=Clark|first3=Catherine A.|last3=Forster|first4=Mark A.|last4=Norell|first5=Gregory M.|last5=Erickson|first6=David A.|last6=Eberth|first7=Chengkai|last7=Jia|first8=Qi|last8=Zhao|url-access=subscription}}</ref><ref>{{Cite book|title=New Perspectives on the Origin and Early Evolution of Birds|last=Sereno|first=Paul|publisher=Peabody Museum of Natural History Yale University|year=2001|isbn=978-0-912532-57-8|editor-last=Gauthier|editor-first=Jacques|chapter=Alvarezsaurids: Birds or ornithomimosaurs?|editor-last2=Ostrom|editor-first2=John H.}}</ref><ref>{{Cite journal|title=The Evolution of Dinosaurs|url=https://www.science.org/doi/10.1126/science.284.5423.2137|journal=Science|date=1999-06-25|pages=2137–2147|volume=284|issue=5423|doi=10.1126/science.284.5423.2137|first=Paul C.|last=Sereno|url-access=subscription}}</ref>
Characteristic features of the tyrannosauroid pelvis include a concave notch at the upper front end of the ilium, a sharply defined vertical ridge on the outside surface of the ilium, extending upwards from the acetabulum (hip socket), and a huge "boot" on the end of the pubis, more than half as long as the shaft of the pubis itself.<ref name=holtz2004/> These features are found in all known tyrannosauroids, including basal members ''Guanlong''<ref name=xuetal2006/> and ''Dilong''.<ref name=xuetal2004/> The pubis is not known in ''Aviatyrannis'' or ''Stokesosaurus'' but both show typical tyrannosauroid characters in the ilium.<ref name=rauhut2003a>{{cite journal |last=Rauhut |first=Oliver W.M. |year=2003 |title=A tyrannosauroid dinosaur from the Upper Jurassic of Portugal |journal=Palaeontology |volume=46 |issue=5 |pages=903–910 |doi=10.1111/1475-4983.00325|bibcode=2003Palgy..46..903R |doi-access=free }}</ref> The hindlimbs of all tyrannosauroids, like most theropods, had four toes, although the first toe (the hallux) did not contact the ground. Tyrannosauroid hindlimbs are longer relative to body size than almost any other theropods, and outside of the largest forms show proportions characteristic of fast-running animals, including elongated tibiae and metatarsals.<ref name=holtz2004/> Elongated metatarsals are present even in the largest adult ''Tyrannosaurus'' in spite of the tibiae being proportionately shorter than in smaller tyrannosauroids<ref name="brochu2003">{{cite journal |last=Brochu |first=Christopher R. |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 |url=http://www.vertpaleo.org/publications/memoirs.cfm |doi=10.2307/3889334 |jstor=3889334 |archive-url=https://web.archive.org/web/20071212211311/http://www.vertpaleo.org/publications/memoirs.cfm |archive-date=2007-12-12 |url-access=subscription }}</ref> and a probable inability to run (i.e move with an aerial phase where both feet are off the ground).<ref name=hutchinsongarcia2002>{{cite journal |last=Hutchinson |first=John R. |author2=& Garcia, Mariano. |year=2002 |title=''Tyrannosaurus'' was not a fast runner |journal=Nature |volume=415 |issue=6875 |pages=1018–1021 |doi=10.1038/4151018a |pmid=11875567 |bibcode=2002Natur.415.1018H |s2cid=4389633 |url=http://doc.rero.ch/record/15515/files/PAL_E2919.pdf |archive-date=2023-02-02 |access-date=2023-01-03 |archive-url=https://web.archive.org/web/20230202192031/https://doc.rero.ch/record/15515/files/PAL_E2919.pdf |url-status=live }}</ref> The third metatarsal of tyrannosaurids, including in the very largest forms, was pinched at the top between the second and fourth, forming a structure known as the arctometatarsus that aided in energy conservation and, in smaller forms, increased speed.<ref name=holtz2004/> The arctometatarsus was also present in ''Appalachiosaurus''<ref name=carretal2005/> but it is unclear whether it was found in ''Eotyrannus''<ref name=huttetal2001/> or ''Dryptosaurus''.<ref name=carpenteretal1997>{{cite journal |doi=10.1080/02724634.1997.10011003 |last=Carpenter |first=Kenneth |author-link=Kenneth Carpenter |author2=Russell, Dale A. |year=1997 |title=Redescription of the holotype of ''Dryptosaurus aquilunguis'' (Dinosauria: Theropoda) from the Upper Cretaceous of New Jersey |journal=Journal of Vertebrate Paleontology |volume=17 |issue=3 |pages=561–573 |bibcode=1997JVPal..17..561C |url=http://www.vertpaleo.org/publications/jvp/17-561-573.cfm |author-link2=Dale Russell |archive-url=https://web.archive.org/web/20100715095911/http://www.vertpaleo.org/publications/jvp/17-561-573.cfm |archive-date=2010-07-15 |url-access=subscription }}</ref> This structure was shared by derived ornithomimids, troodontids and 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 |url=http://jpaleontol.geoscienceworld.org/cgi/content/abstract/68/5/1100 |doi=10.1017/S0022336000026706 |bibcode=1994JPal...68.1100H |s2cid=129684676 |archive-date=2008-10-13 |access-date=2007-12-15 |archive-url=https://web.archive.org/web/20081013025427/http://jpaleontol.geoscienceworld.org/cgi/content/abstract/68/5/1100 |url-status=live |url-access=subscription }}</ref> but was not present in basal tyrannosauroids like ''Dilong paradoxus'', indicating convergent evolution.<ref name=xuetal2004/>
==Classification== [[File:Proceratosaurus_holotype_skull.jpg|thumb|200x200px|Skull of ''Proceratosaurus'', a proceratosaurid tyrannosauroid from the Middle Jurassic of England.|left]] ''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 |hdl=2246/1464 |doi=10.1111/j.1468-5965.2007.00735_17.x |issue=3}}</ref> The name is derived from the Ancient Greek words ''{{lang|grc|τυραννος}}'' ''{{lang|grc-Latn|tyrannos}}'' ('tyrant') and {{lang|grc|σαυρος}} ''{{lang|grc-Latn|sauros}}'' ('lizard'). The superfamily name Tyrannosauroidea was first published in a 1964 paper by the British paleontologist Alick Walker.<ref name=walker1964>{{cite journal |last=Walker |first=Alick D. |author-link=Alick Walker |year=1964 |title=Triassic reptiles from the Elgin area: ''Ornithosuchus'' and the origin of carnosaurs |journal=Philosophical Transactions of the Royal Society of London. Series B, Biological Sciences |volume=248 |pages=53–134 |doi=10.1098/rstb.1964.0009 |bibcode=1964RSPTB.248...53W |issue=744|s2cid=86378219 |doi-access= }}</ref> The suffix ''-oidea'', commonly used in the name of animal superfamilies, is derived from the Greek ''ειδος'' ''{{lang|grc-Latn|eidos}}'' ('form').<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-access=registration |url=https://archive.org/details/lexicon00lidd }}</ref>
Scientists have commonly understood Tyrannosauroidea to include the tyrannosaurids and their immediate ancestors.<ref name=walker1964/><ref name=bonaparteetal1990>{{cite book |last=Bonaparte |first=José F. |author-link=José Bonaparte |author2=Novas, Fernando E. |year=1990 |title=''Carnotaurus sastrei'' Bonaparte, the horned, lightly built carnosaur from the Middle Cretaceous of Patagonia |series=Contributions in Science |publisher=Natural History Museum of Los Angeles County |author-link2=Fernando Novas |oclc=21966322 }}{{page needed|date=December 2019}}</ref> With the advent of phylogenetic taxonomy in vertebrate paleontology, however, the clade has received several more explicit definitions. The first was by Paul Sereno in 1998, where Tyrannosauroidea was defined as a stem-based taxon including all species sharing a more recent common ancestor with ''Tyrannosaurus rex'' than with neornithean birds.<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 |issue=1 |pages=41–83 |doi=10.1127/njgpa/210/1998/41 }}</ref> To make the family more exclusive, Thomas Holtz redefined it in 2004 to include all species more closely related to ''Tyrannosaurus rex'' than to ''Ornithomimus velox'', ''Deinonychus antirrhopus'' or ''Allosaurus fragilis''.<ref name=holtz2004/> Sereno published a new definition in 2005, using ''Ornithomimus edmontonicus'', ''Velociraptor mongoliensis'' and ''Troodon formosus'' as external specifiers.<ref name=sereno2005>{{cite web |last=Sereno |first=Paul C. |author-link=Paul Sereno |year=2005 |url=http://www.taxonsearch.org/dev/taxon_edit.php?Action=View&tax_id=350 |title=Stem Archosauria — TaxonSearch, Version 1.0 |access-date=2007-12-10 |archive-url=https://web.archive.org/web/20071226232214/http://www.taxonsearch.org/dev/taxon_edit.php?Action=View&tax_id=350 |archive-date=2007-12-26 }}</ref> The Sereno definition was adopted in a 2010 review.<ref name=BrusatteEtAl2010/>
Some studies have suggested that the clade Megaraptora, usually considered to be allosauroids, are basal tyrannosauroids.<ref name=novas2012>{{cite journal | author1=F. E. Novas | author2=F. L. Agnolín | author3=M. D. Ezcurra | author4=J. I. Canale | author5=J. D. Porfiri | year=2012 | title=Megaraptorans as members of an unexpected evolutionary radiation of tyrant-reptiles in Gondwana | url=http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/868/1618 | journal=Ameghiniana | volume=49 | issue=Suppl | pages=R33 | archive-date=2016-03-11 | access-date=2015-10-23 | archive-url=https://web.archive.org/web/20160311112309/http://www.ameghiniana.org.ar/index.php/ameghiniana/article/view/868/1618 | url-status=live }}</ref><ref name="Porfiri2014">{{cite journal |last1=Porfiri |first1=Juan D. |last2=Novas |first2=Fernando E. |last3=Calvo |first3=Jorge O. |last4=Agnolín |first4=Federico L. |last5=Ezcurra |first5=Martín D. |last6=Cerda |first6=Ignacio A. |title=Juvenile specimen of Megaraptor (Dinosauria, Theropoda) sheds light about tyrannosauroid radiation |journal=Cretaceous Research |date=September 2014 |volume=51 |pages=35–55 |doi=10.1016/j.cretres.2014.04.007 |bibcode=2014CrRes..51...35P |hdl=11336/12129|hdl-access=free }}</ref> However, other authors disputed the placement of megaraptorans within Tyrannosauroidea,<ref>{{cite journal | last1 = Yun | first1 = C | year = 2015 | title = Comments on the juvenile Megaraptor specimen and systematic positions of megaraptoran theropods | journal = PeerJ PrePrints | volume = 3 | page = e1051 | doi=10.7287/peerj.preprints.851v1 | doi-access = free }}</ref><ref name="A large-clawed theropod Dinosauria">{{cite journal |last1=Bell |first1=Phil R. |last2=Cau |first2=Andrea |last3=Fanti |first3=Federico |last4=Smith |first4=Elizabeth T. |title=A large-clawed theropod (Dinosauria: Tetanurae) from the Lower Cretaceous of Australia and the Gondwanan origin of megaraptorid theropods |journal=Gondwana Research |date=August 2016 |volume=36 |pages=473–487 |doi=10.1016/j.gr.2015.08.004 |bibcode=2016GondR..36..473B }}</ref> and a study of megaraptoran hand anatomy published in 2016 caused even the original scientists suggesting their tyrannosauroid relationships to at least partly reject their prior conclusion.<ref name=novasetal2016>{{cite journal |last1=Novas |first1=Fernando E. |last2=Rolando |first2=Alexis M. Aranciaga |last3=Agnolín |first3=Federico L. |title=Phylogenetic relationships of the Cretaceous Gondwanan theropods Megaraptor and Australovenator: the evidence afforded by their manual anatomy |journal=Memoirs of Museum Victoria |year=2016 |volume=74 |pages=49–61 |doi=10.24199/j.mmv.2016.74.05 |doi-access=free |hdl=11336/48895 |hdl-access=free }}</ref>
===Phylogeny=== While paleontologists have long recognized the family Tyrannosauridae, its ancestry has been the subject of much debate. For most of the twentieth century, tyrannosaurids were commonly accepted as members of the Carnosauria, which included almost all large theropods.<ref name=romer1956>{{cite book |last=Romer |first=Alfred S. |author-link=Alfred Sherwood Romer |year=1956 |title=Osteology of the Reptiles |location=Chicago |publisher=University of Chicago Press |isbn=978-0-89464-985-1 }}{{page needed|date=December 2019}}</ref><ref name=gauthier1986>{{cite book |last=Gauthier |first=Jacques |author-link=Jacques Gauthier |year=1986 |chapter=Saurischian monophyly and the origin of birds |editor=Padian, Kevin |title=The Origin of Birds and the Evolution of Flight |series=''Memoirs of the California Academy of Sciences'' '''8''' |pages=1–55 |isbn=978-0-940228-14-6 |publisher=Published by California Academy of Sciences |location=San Francisco, CA}}</ref> Within this group, the allosaurids were often considered to be ancestral to tyrannosaurids.<ref name=bonaparteetal1990/><ref name=molnaretal990>{{cite book |last=Molnar |first=Ralph E. |author-link=Ralph Molnar |author2=Kurzanov, Sergei M. |year=1990 |chapter=Carnosauria |editor= Weishampel, David B. |editor2=Dodson, Peter |editor3=Osmólska, Halszka |title=The Dinosauria |edition=First |publisher=University of California Press |location=Berkeley |pages=169–209 |isbn=978-0-520-06727-1|author-link2=Sergei Kurzanov }}</ref> In the early 1990s, cladistic analyses instead began to place tyrannosaurids into the Coelurosauria,<ref name=holtz1994/><ref name=novas1992>{{cite book |last=Novas |first=Fernando E. |author-link=Fernando Novas |year=1992 |chapter=La evolución de los Dinosaurios carnívoros |trans-chapter=The evolution of the carnivorous dinosaurs |language=es |editor1-last=Sanz |editor1-first=José L. |editor2-last=Buscalioni |editor2-first=Angela D. |title=Los Dinosaurios y su entorno biotico |trans-title=Dinosaurs and their biotic environment |location=Cuenca |publisher=Instituto Juan de Valdés |pages=125–163 |isbn=978-84-86788-14-8 }}</ref> echoing suggestions first published in the 1920s.<ref name=matthewbrown1922>{{cite journal |last=Matthew |first=William D. |author-link=William Diller Matthew |author2=Brown, Barnum |year=1922 |title=The family Deinodontidae, with notice of a new genus from the Cretaceous of Alberta |journal=Bulletin of the American Museum of Natural History |volume=46 |pages=367–385 |hdl=2246/1300|author-link2=Barnum Brown }}</ref><ref name=vonhuene1923>{{cite journal |last=von Huene |first=Friedrich |author-link=Friedrich von Huene |title=Carnivorous Saurischia in Europe since the Triassic |journal=Geological Society of America Bulletin |volume=34 |issue=3 |pages=449–458|bibcode=1923GSAB...34..449V |year=1923 |doi=10.1130/GSAB-34-449 }}</ref> Tyrannosaurids are now universally considered to be large coelurosaurs.<ref name=holtz2004/><ref name=xuetal2006/><ref name="senter2007">{{cite journal |last=Senter |first=Phil |year=2007 |title=A new look at the phylogeny of Coelurosauria (Dinosauria, Theropoda) |journal=Journal of Systematic Palaeontology |volume=5 |issue=4 |pages=429–463 |doi=10.1017/S1477201907002143|bibcode=2007JSPal...5..429S |s2cid=83726237 }}</ref><ref name=sereno1999>{{cite journal |last=Sereno |first=Paul C. |author-link=Paul Sereno |year=1999 |title=The evolution of dinosaurs |journal=Science |volume=284 |issue=5423 |pages=2137–2147 |doi=10.1126/science.284.5423.2137 |pmid=10381873}}</ref><ref name=rauhut2003b>{{cite book |last=Rauhut |first=Oliver W.M. |year=2003 |title=The interrelationships and evolution of basal theropod dinosaurs |journal=Special Papers in Palaeontology |volume=69 |pages=1–213 |isbn=978-0-901702-79-1}}</ref><ref name=currieetal2003>{{cite journal |last=Currie |first=Philip J. |author2=Hurum, Jørn H; & 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://app.pan.pl/archive/published/app48/app48-227.pdf |archive-date=2009-03-26 |access-date=2010-06-12 |archive-url=https://web.archive.org/web/20090326062829/http://app.pan.pl/archive/published/app48/app48-227.pdf |url-status=live }}</ref><ref name=norelletal2006>{{cite journal |last=Norell |first=Mark A. |author2=Barsbold, Rinchen |year=2006 |title=A new dromaeosaurid theropod from Ukhaa Tolgod (Ömnögov, Mongolia) |journal=American Museum Novitates |issue= 3545 |pages=1–51 |hdl=2246/5823 |doi=10.1206/0003-0082(2006)3545[1:ANDTFU]2.0.CO;2 |author-link2=Rinchen Barsbold |url=http://digitallibrary.amnh.org/bitstream/2246/5823/1//v3/dspace/updateIngest/pdfs/N3545.pdf }}</ref>
In 1994, Holtz grouped tyrannosauroids with elmisaurids, ornithomimosaurs and troodonts into a coelurosaurian clade called Arctometatarsalia based on a common ankle structure where the second and fourth metatarsals meet near the tarsal bones, covering the third metatarsal when viewed from the front.<ref name=holtz1994/> Basal tyrannosauroids like ''Dilong'', however, were found with non-arctometatarsalian ankles, indicating that this feature evolved convergently.<ref name=xuetal2004/> Arctometatarsalia has been dismantled and is no longer used by most paleontologists, with tyrannosauroids usually considered to be basal coelurosaurs outside Maniraptoriformes.<ref name=holtz2004/><ref name=rauhut2003b/><ref name=norelletal2006/> While many place tyrannosauroids as basal coelurosaurs, Paul Sereno in his 1990s analysis of theropods would find the Tyrannosaurs to be sister taxa to the Maniraptora with them being closer to birds than Ornithomimosaurs were. He called this group Tyrannoraptora (which in the absence of papers that recover a Tyrannosaur-maniraptoran clade), is a clade which contains most Coelurosaurs.<ref>{{cite journal |last1=Sereno |first1=Paul |title=The Evolution of Dinosaurs |journal=Science |date=1999 |volume=284 |issue=5423 |pages=2137–2147 |doi=10.1126/science.284.5423.2137 |pmid=10381873 |url=https://www.science.org/doi/10.1126/science.284.5423.2137 |archive-date=2022-09-21 |access-date=2022-08-30 |archive-url=https://web.archive.org/web/20220921125519/https://www.science.org/doi/10.1126/science.284.5423.2137 |url-status=live |url-access=subscription }}</ref> A 2007 analysis found the family Coeluridae, including the Late Jurassic North American genera ''Coelurus'' and ''Tanycolagreus'', to be the sister group of Tyrannosauroidea.<ref name=senter2007/>
The most basal tyrannosauroid known from complete skeletal remains is ''Guanlong,'' a representative of the family Proceratosauridae.<ref name=xuetal2006/><ref name=ORetal2009>{{cite journal |last=Rauhut|first=Oliver W. M. |author2=Milner, Angela C. |author3= Moore-Fay, Scott |year=2010 |title=Cranial osteology and phylogenetic position of the theropod dinosaur ''Proceratosaurus bradleyi'' (Woodward, 1910) from the Middle Jurassic of England |journal=Zoological Journal of the Linnean Society |volume=158 |doi=10.1111/j.1096-3642.2009.00591.x |pages=155–195|doi-access=free }}</ref> Other early taxa include ''Stokesosaurus'' and ''Aviatyrannis'', known from far less complete material.<ref name=rauhut2003a/> The better-known ''Dilong'' is considered slightly more derived than ''Guanlong'' and ''Stokesosaurus''.<ref name=xuetal2004/><ref name=xuetal2006/> ''Dryptosaurus'', long a difficult genus to classify, has turned up in several recent analyses as a basal tyrannosauroid as well, slightly more distantly related to Tyrannosauridae than ''Eotyrannus'' and ''Appalachiosaurus''.<ref name=holtz2004/><ref name=carretal2005/><ref name=holtzdml2005>{{cite web |last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |date=2005-09-20 |url=http://dml.cmnh.org/2005Sep/msg00345.html |title=RE: Burpee Conference (LONG) |work=Archives of the Dinosaur Mailing List |access-date=2007-06-18 |archive-date=2016-04-12 |archive-url=https://web.archive.org/web/20160412171657/http://dml.cmnh.org/2005Sep/msg00345.html }}</ref> ''Alectrosaurus'', a poorly known genus from Mongolia, is definitely a tyrannosauroid but its exact relationships are unclear.<ref name=holtz2004/> Other taxa have been considered possible tyrannosauroids by various authors, including ''Bagaraatan'' and ''Labocania''.<ref name=holtz2004/> ''Siamotyrannus'' from the Early Cretaceous of Thailand was originally described as an early tyrannosaurid,<ref name=buffetautetal1996>{{cite journal |last=Buffetaut |first=Eric |author2=Suteethorn, Varavudh; & Tong Haiyan |year=1996 |title=The earliest known tyrannosaur from the Lower Cretaceous of Thailand |journal=Nature |volume=381 |issue=6584 |pages=689–691 |doi=10.1038/381689a0|bibcode=1996Natur.381..689B |last3=Tong |first3=Haiyan |s2cid=7350556 }}</ref> but is usually considered a carnosaur today.<ref name=rauhut2003b/><ref name=holtzetal2004>{{cite book |last=Holtz |first=Thomas R. |author-link=Thomas R. Holtz Jr. |author2=Molnar, Ralph E. |year=2004 |chapter=Basal Tetanurae |editor=Weishampel, David B. |editor2=Dodson, Peter |editor3=Osmólska, Halszka |title=The Dinosauria |edition=Second |publisher=University of California Press |location=Berkeley |pages=71–110 |isbn=978-0-520-24209-8|author-link2=Ralph Molnar }}</ref> ''Iliosuchus'' has a vertical ridge on the ilium reminiscent of tyrannosauroids and may in fact be the earliest known member of the superfamily, but not enough material is known to be sure.<ref name=rauhut2003a/><ref name=holtzetal2004/>
Below on the left is a cladogram of Tyrannosauroidea from a 2022 study by Darren Naish and Andrea Cau on the genus ''Eotyrannus'', and on the right is a cladogram of Eutyrannosauria from a 2020 study by Jared T. Voris and colleagues on the genus ''Thanatotheristes'':<ref name=monograph>{{cite journal |last1= Naish |first1= D. |last2= Cau |first2= A. |date= July 2022 |title= The osteology and affinities of ''Eotyrannus lengi'', a tyrannosauroid theropod from the Wealden Supergroup of southern England |journal= PeerJ |volume= 10 |article-number= e12727 |doi= 10.7717/peerj.12727|pmid= 35821895 |pmc= 9271276 |doi-access= free }}</ref><ref name="Voris2020">{{Cite journal |last1=Voris |first1=Jared T. |last2=Therrien |first2=Francois |last3=Zelenitzky |first3=Darla K. |last4=Brown |first4=Caleb M. |year=2020 |title=A new tyrannosaurine (Theropoda:Tyrannosauridae) from the Campanian Foremost Formation of Alberta, Canada, provides insight into the evolution and biogeography of tyrannosaurids |journal=Cretaceous Research |volume=110 |article-number=104388 |doi=10.1016/j.cretres.2020.104388|bibcode=2020CrRes.11004388V |s2cid=213838772 }}</ref>
{| width="100%" |- valign="top" | align="left" width="50%" | {{clade| style=font-size:95%; line-height:95% |label1='''Tyrannosauroidea''' |1={{clade |1={{clade |1=''Juratyrant'' 80px |2=''Stokesosaurus'' 80px }} |2={{clade |1=Coeluridae <div style="{{MirrorH}}">80px</div> |2={{clade |label1=Proceratosauridae |1={{clade |1=''Dilong'' |2={{clade |1=''Guanlong'' 80px |2={{clade |1=''Proceratosaurus'' |2=''Sinotyrannus'' 80px }} }} }} |2={{clade |1=''Yutyrannus'' 80px |2={{clade |1=''Eotyrannus'' <div style="{{MirrorH}}">80px</div> |2={{clade |1=''Xiongguanlong'' 70px |2={{clade |label1=Megaraptora |1={{clade |1=''Siats'' 80px |2={{clade |1=''Aniksosaurus'' |2={{clade |1=''Chilantaisaurus'' <div style="{{MirrorH}}">80px</div> |2={{clade |label2=Megaraptoridae |1=''Fukuiraptor'' |2={{clade |1=''Aerosteon'' <div style="{{MirrorH}}">80px</div> |2=''Australovenator'' 80px |3=''Megaraptor'' 80px |4=''Orkoraptor'' 80px }} }} }} }} }} |2={{clade |1=''Dryptosaurus'' 80px |2={{clade |1=''Appalachiosaurus'' 80px |2={{clade |1={{clade |1=''Bistahieversor'' |2=''Teratophoneus'' <div style="{{MirrorH}}">80px</div> }} |2=Tyrannosauridae 80px }} }} }} }} }} }} }} }} }} }} }} | align="left" width="50%"| {{clade| style=font-size:95%; line-height:95% |label1='''Eutyrannosauria''' |1={{clade |1=''Dryptosaurus aquilunguis'' 80px |2={{clade |1=''Appalachiosaurus montgomeriensis'' 80px |2={{clade |1=''Bistahieversor sealeyi'' |2={{clade |label1=Tyrannosauridae |1={{clade |label1=Albertosaurinae |1={{clade |1=''Gorgosaurus libratus'' 80px |2=''Albertosaurus sarcophagus'' 80px}} |label2=Tyrannosaurinae |2={{clade |label1=Alioramini |1={{clade |1=''Qianzhousaurus sinensis'' |2={{clade |1=''Alioramus remotus'' |2=''Alioramus altai'' 80px }} }} |2={{clade |1={{clade |1=''Teratophoneus curriei'' |2=''Dynamoterror dynastes'' |3=''Lythronax argestes'' 80px }} |2={{clade |1=''Nanuqsaurus hoglundi'' 80px |2={{clade |label1=Daspletosaurini |1={{clade |1=''Thanatotheristes degrootorum'' |2={{clade |1=''Daspletosaurus torosus'' 80px |2=''Daspletosaurus horneri''}} }} |2={{clade |1=''Zhuchengtyrannus magnus'' |2={{clade |1=''Tarbosaurus bataar'' 80px |2=''Tyrannosaurus rex'' 80px }} }} }} }} }} }} }} }} }} }} }} }} | align="right" width="50%" | |}
====Phylogeography==== In 2018 authors Rafael Delcourt and Orlando Nelson Grillo published a phylogenetic analysis of Tyrannosauroidea which incorporated taxa from the ancient continent of Gondwana (which today consists of the southern hemisphere), such as ''Santanaraptor'' and ''Timimus'', whose placement in the group has been controversial.<ref name=SouthernTyrannosaur>{{Cite journal | last1 = Delcourt | first1 = R. | last2 = Grillo | first2 = O. N. | title = Tyrannosauroids from the Southern Hemisphere: Implications for biogeography, evolution, and taxonomy | doi = 10.1016/j.palaeo.2018.09.003 | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 511 | pages = 379–387 | year = 2018 | bibcode = 2018PPP...511..379D | s2cid = 133830150 }}</ref> They have found that not only ''Santanaraptor'' and ''Timimus'' were placed as tyrannosaurs more derived than ''Dilong'', but they have found in their analysis that tyrannosauroids were widespread in Laurasia and Gondwana since the Middle Jurassic.<ref name=SouthernTyrannosaur/> They have proposed new subclade names for Tyrannosaurioidea. The first is '''Pantyrannosauria''' referring to all non-proceratosaurid members of the group, while '''Eutyrannosauria''' for larger tyrannosaur taxa found in the northern hemisphere such as ''Dryptosaurus'', ''Appalachiosaurus'', ''Bistahieversor'', and Tyrannosauridae.<ref name=SouthernTyrannosaur/> Below is their phylogeographic tree they have recovered, in which displays the phylogenetic relationships of the taxa as well as the continents those taxa have been found.<ref name=SouthernTyrannosaur/>
{{clade| style=font-size:75%; line-height:75% |label1='''Tyrannosauroidea''' |1={{clade |label1=Proceratosauridae |1={{clade |1={{clade |1=''Guanlong wucaii'' 20px |2={{Clade |1=''Proceratosaurus bradleyi'' 20px |2={{Clade |1=''Kileskus aristotocus'' 20px |2={{clade |1=''Sinotyrannus kazuoensis'' 20px |2=''Yutyrannus huali'' 20px }} }} }} }} }} |label2='''Pantyrannosauria''' |2={{clade |1={{clade |1=''Aviatyrannis jurassica'' 20px |2={{clade |1=''Dilong paradoxus'' 20px |2={{clade |label1= |1={{clade |1=''Santanaraptor placidus'' 20px |2=''Timimus hermani'' 20px |3={{clade |label1= |1={{clade |1=''Stokesosaurus clevelandi'' 20px |2=''Juratyrant langhami'' 20px |3=''Eotyrannus lengi'' 20px}} |label2= |2={{clade |1=''Xiongguanlong baimoensis'' 20px |2=NMV P186046 ("Australian tyrannosaur") 20px |3={{clade |label1= |1={{clade |1=''Alectrosaurus olseni'' 20px |2=''Timurlengia euotica'' 20px}} |label2='''Eutyrannosauria''' |2={{clade |1=''Dryptosaurus aquilunguis'' 20px |2={{clade |1=''Appalachiosaurus montgomeriensis'' 20px |2={{clade |1=''Bistahieversor sealeyi'' 20px |2={{clade |label1=Tyrannosauridae |1=TYRANNOSAURIDAE }} }} }} }} }} }} }} }} }} }} }} }} }} |targetA=TYRANNOSAURIDAE |subcladeA={{clade |label1=Albertosaurinae |1={{clade |1=''Gorgosaurus libratus'' 20px |2=''Albertosaurus sarcophagus'' 20px}} |label2=Tyrannosaurinae |2={{clade |label1=Alioramini |1={{clade |1=''Qianzhousaurus sinensis'' 20px |2={{clade |1=''Alioramus remotus'' 20px |2=''Alioramus altai'' 20px}} }} |label2= |2={{clade |1=''Nanuqsaurus hoglundi'' 20px |2=''Teratophoneus curriei'' 20px |3=''Lythronax argestes'' 20px |4={{clade |label1= |1={{clade |label1= |1={{clade |1=''Daspletosaurus torosus'' 20px |2=''Daspletosaurus horneri'' 20px}} }} |label2= |2={{clade |1=''Zhuchengtyrannus magnus'' 20px |2={{clade |1=''Tarbosaurus bataar'' 20px |2=''Tyrannosaurus rex'' 20px }} }} }} }} }} }} }}
In 2021, Chase Brownstein published a research article based on more thorough descriptions of tyrannosauroid metatarsals and vertebra from the Merchantville Formation in Delaware.<ref name=Dryptosauridae>{{Cite journal | last = Brownstein | first = C. | title = Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America | doi = 10.1098/rsos.210127 | doi-access = free| journal = Royal Society Open Science | year = 2021 | volume = 8 | issue = 8 | article-number = 210127 | pmid = 34457333 | pmc = 8385347 | bibcode = 2021RSOS....810127D }}</ref> This reanalysis of phylogenetic relationships of tyrannosauroids in Appalachia has brought the rediscovery of the clade Dryptosauridae due to the similarities of metatarsals II and IV with the same bones in the ''Dryptosaurus'' holotype.<ref name=Dryptosauridae/> However. the Merchantville taxon was found to still be different enough to separate it on the genus level from ''Dryptosaurus''. In the phylogentic tree constructed Dryptosauridae is found to be a valid family of non tyrannosaurid eutyrannosaur. It currently sits in a polytomy with the Iren Dabasu taxon and more basal eutryannosaurs.<ref name=Dryptosauridae/>
==Distribution== thumb|Visual showing the geographic, cladistic, and chronological distribution of the Tyrannosauroidea clade The tyrannosauroids lived on the supercontinent Laurasia, which split from Gondwana in the Middle Jurassic. The earliest recognized tyrannosauroids lived in the Middle Jurassic, represented by the proceratosaurids ''Kileskus'' from the Western Siberia and ''Proceratosaurus'' from Great Britain. Upper Jurassic tyrannosauroids include ''Guanlong'' from China'','' ''Stokesosaurus'' from the western United States and ''Aviatyrannis'' and ''Juratyrant'' from Europe. {{cn|date=May 2026}} thumb|right|450px|Confirmed tyrannosauroid fossils have only been discovered in the northern continents, with possible basal tyrannosauroid fossils reported from Australia. Late Cretaceous tyrannosauroids are known only from North America and Asia.
Early Cretaceous tyrannosauroids are known from Laurasia, being represented by ''Eotyrannus'' from England<ref name=huttetal2001/> and ''Dilong'', ''Sinotyrannus'', and ''Yutyrannus'' from northeastern China. Early Cretaceous tyrannosauroid premaxillary teeth are known from the Cedar Mountain Formation in Utah<ref name=kirklandetal1997>{{cite journal |last=Kirkland |first=James I. |author-link=James Kirkland (paleontologist) |author2=Carpenter, Kenneth |year=1997 |title=Lower to Middle Cretaceous Dinosaur faunas of the central Colorado Plateau: a key to understanding 35 million years of tectonics, sedimentology, evolution, and biogeography |journal=Brigham Young University Geology Studies |volume=42 |issue=II |pages=69–103|author-link2=Kenneth Carpenter }}</ref> and the Tetori Group of Japan.<ref name=manabe1999>{{cite journal |last=Manabe |first=Makoto |year=1999 |title=The early evolution of the Tyrannosauridae in Asia |journal=Journal of Paleontology |volume=73 |issue=6 |pages=1176–1178 |url=http://jpaleontol.geoscienceworld.org/cgi/content/abstract/73/6/1176 |doi=10.1017/S002233600003105X |bibcode=1999JPal...73.1176M |s2cid=130306877 |archive-date=2007-12-27 |access-date=2007-12-15 |archive-url=https://web.archive.org/web/20071227070606/http://jpaleontol.geoscienceworld.org/cgi/content/abstract/73/6/1176 |url-status=live |url-access=subscription }}</ref>
The Middle Cretaceous record of Tyrannosauroidea is rather patchy. Teeth and indeterminate postcrania of this interval are known from the Cenomanian-age Dakota Formation of western North America and Potomac Formation of New Jersey,<ref name=kirklandetal1997/><ref>{{cite journal |last1=Brownstein |first1=Chase Doran |title=A Tyrannosauroid from the Lower Cenomanian of New Jersey and Its Evolutionary and Biogeographic Implications |journal=Bulletin of the Peabody Museum of Natural History |date=April 2018 |volume=59 |issue=1 |pages=95–105 |doi=10.3374/014.058.0210 |bibcode=2018BPMNH..59...95B |s2cid=90633156 }}</ref> as well as formations in Kazakhstan and Tajikistan;<ref name=nesov1995>{{cite book |last=Nesov |first=Lev A. |year=1995 |title=Dinosaurs of Northern Eurasia: new data about assemblages, ecology and paleobiogeography |publisher=Scientific Research Institute of the Earth's Crust, St. Petersburg State University |location=St. Petersburg |language=ru |page=156pp}}</ref> two genera, ''Timurlengia'' and ''Xiongguanlong'', have been found in Asia, while the Brazilian ''Santanaraptor'' may belong to this group.<ref name="A large-clawed theropod Dinosauria"/> ''Suskityrannus'' has been found in the Moreno Hill Formation of the Zuni Basin of western New Mexico.<ref>{{cite journal | last1 = Mcdonald | first1 = Wolfe | last2 = Kirkland | year = 2010 | title = A new basal hadrosauroid (Dinosauria: Ornithopoda) from the Turonian of New Mexico | journal = Journal of Vertebrate Paleontology | volume = 30 | issue = 3| pages = 799–812 | doi=10.1080/02724631003763516| bibcode = 2010JVPal..30..799M | s2cid = 86614424 }}</ref><ref>{{cite journal |author1=Sterling J. Nesbitt |author2=Robert K. Denton Jr |author3=Mark A. Loewen |author4=Stephen L. Brusatte |author5=Nathan D. Smith |author6=Alan H. Turner |author7=James I. Kirkland |author8=Andrew T. McDonald |author9=Douglas G. Wolfe |year=2019 |title=A mid-Cretaceous tyrannosauroid and the origin of North American end-Cretaceous dinosaur assemblages |journal=Nature Ecology & Evolution |volume=3 |issue=6 |pages=892–899 |doi=10.1038/s41559-019-0888-0 |pmid=31061476 |bibcode=2019NatEE...3..892N |s2cid=146115938 |url=https://www.pure.ed.ac.uk/ws/files/82474043/82473554._Brusatte._AAM.pdf |hdl=20.500.11820/a6709b34-e3ab-416e-a866-03ba1162b23d |hdl-access=free |archive-date=2021-04-13 |access-date=2019-12-10 |archive-url=https://web.archive.org/web/20210413074456/https://www.pure.ed.ac.uk/ws/files/82474043/82473554._Brusatte._AAM.pdf |url-status=live }}</ref> The first unquestionable remains of tyrannosaurids occur in the Campanian stage of the Late Cretaceous in North America and Asia. Two subfamilies are recognized. The albertosaurines are only known from North America, while the tyrannosaurines are found on both continents.<ref name=holtz2004/> Tyrannosaurid fossils have been found in Alaska, which may have served as a land bridge allowing dispersal between the two continents.<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 }}</ref> Non-tyrannosaurid tyrannosauroids like ''Alectrosaurus'' and possibly ''Bagaraatan'' were contemporaneous with tyrannosaurids in Asia, while they are absent from western North America.<ref name=holtz2004/> Eastern North America was divided by the Western Interior Seaway in the middle of the Cretaceous and isolated from the western portion of the continent. The absence of tyrannosaurids from the eastern part of the continent suggests that the family evolved after the appearance of the seaway, allowing basal tyrannosauroids like ''Dryptosaurus'' and ''Appalachiosaurus'' to survive in the east as a relict population until the end of the Cretaceous.<ref name=carretal2005/>
Basal tyrannosauroids have also been suggested to be present in Australia and South America during the Early Cretaceous. NMV P186069, a partial pubis (a hip bone) with a supposed distinctive tyrannosauroid-like form, was discovered in Dinosaur Cove in Victoria.<ref name=RBetal10>{{cite journal |last=Benson |first=R. B. J. |author2=Barrett, P. M. |author3=Rich, T. H. |author4=Vickers-Rich, P. |year=2010 |title=A southern tyrant reptile |journal=Science |pmid=20339066 |volume=327 |issue=5973 |page=1613 |doi=10.1126/science.1187456 |bibcode=2010Sci...327.1613B |s2cid=206525597 |url=http://eprints.esc.cam.ac.uk/1361/1/Benson_et_al_2010_australiantyranno.pdf |access-date=2018-08-06 |archive-date=2018-07-21 |archive-url=https://web.archive.org/web/20180721160226/http://eprints.esc.cam.ac.uk/1361/1/Benson_et_al_2010_australiantyranno.pdf }}</ref> However, a response suggested that critical tyrannosauroid characters were absent from the fossil.<ref>{{Cite journal|last1=Herne|first1=M. C.|last2=Nair|first2=J. P.|last3=Salisbury|first3=S. W.|date=2010-08-27|title=Comment on 'A Southern Tyrant Reptile'|url=https://www.science.org/doi/10.1126/science.1190100|journal=Science|language=en|volume=329|issue=5995|page=1013|doi=10.1126/science.1190100|pmid=20798297|bibcode=2010Sci...329.1013H|s2cid=6772287|url-access=subscription}}</ref> The Australian taxon ''Timimus'', known from a femur, and the Brazilian ''Santanaraptor'', known from a partial juvenile skeleton, have also been suggested to be tyrannosaurs.<ref name="SouthernTyrannosaur" /> However, these placements have been considered questionable, with the supposed tyrannosauroid characters of ''Santanaraptor'' being widely distributed within Coelurosauria, in other characters having similarities to noasaurids.<ref>{{Cite journal|last=Doran Brownstein|first=Chase|title=Dinosaurs from the Santonian–Campanian Atlantic coastline substantiate phylogenetic signatures of vicariance in Cretaceous North America|journal=Royal Society Open Science|year=2021|volume=8|issue=8|article-number=210127|doi=10.1098/rsos.210127|doi-access=free|pmid=34457333|pmc=8385347|bibcode=2021RSOS....810127D}}</ref>
==Paleobiology==
===Facial tissue=== A conference paper by Tracy Ford states that there was rough bone texture on the skulls of theropods and higher foramina frequency than lepidosaurs and mammals which would be evidential for a sensitive snout for theropods.<ref>{{Cite web |last=Ford |first=Tracy |date=January 2015 |title=Tactile Faced Theropods |url=https://www.researchgate.net/publication/314090740 |website=ResearchGate}}</ref><ref>{{Cite journal |last=Ford |first=Tracy |date=1997-11-15 |title=Ford, T. L., 1997, Did Theropods have Lizard Lips?: Southwest Paleontological Symposium – Proceedings, 1997, p. 65-78. |url=https://www.researchgate.net/publication/314090652 |journal=Mesa Southwest Museum and Southwest Paleontological Society |volume=1 |pages=65–78}}</ref> A study in 2017 study on a new tyrannosaurid named ''Daspletosaurus horneri'' was published in the journal Scientific Reports, where paleontologist Thomas Carr analyzed the craniofacial texture of ''Daspletosaurus horneri'' and observed a hummocky rugosity which compared to crocodilian skulls, suggesting ''Daspletosaurus horneri'' and with it all tyrannosaurids have flat sensory scales. The subordinate regions were analyzed to have cornified epidermis.<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|pmid=28358353|pmc=5372470|bibcode=2017NatSR...744942C}}</ref> However, a 2018 presentation has an alternative interpretation. Crocodilians do not have flat sensory scales, but rather cracked, cornified epidermis due to growth. The hummocky rugosity in the skulls of lepidosaurs have correlation with scales which this bone texture is also present in tyrannosaurid skulls. The foramina frequency in theropod skulls does not exceed 50 foramina, which shows that theropods had lips. It's been proposed that lips are a primitive trait in tetrapods and the soft tissue present in crocodilians are a derived trait because of aquatic or semiaquatic adaptations.<ref>{{cite web |last1=Witton |first1=Mark |last2=Hone |first2=David |date=2018 |title=Tyrannosaurid theropods: did they ever smile like crocodiles? p. 67 |url=https://iris.unito.it/bitstream/2318/1703198/1/SVPCA2018AbstractBooklet.pdf |access-date=9 October 2020 |website=The Annual Symposium of Vertebrate Palaeontology and Comparative Anatomy |archive-date=16 July 2022 |archive-url=https://web.archive.org/web/20220716023044/https://iris.unito.it/bitstream/2318/1703198/1/SVPCA2018AbstractBooklet.pdf |url-status=live }}</ref><ref>{{Cite web |last1=Reisz |first1=Robert |last2=Larson |first2=Derek |date=2016 |title=Dental anatomy and skull length to tooth size ratios support the hypothesis that theropod dinosaurs had lips |url=https://cansvp.files.wordpress.com/2013/08/csvp-2016-abstract-book-compressed.pdf |website=4th Annual Meeting, 2016, Canadian Society of Vertebrate Palaeontology.}}</ref><ref>{{Cite web |last=Morhardt |first=Ashely |date=2009 |title=Dinosaur smiles: Do the texture and morphology of the premaxilla, maxilla, and dentary bones of sauropsids provide osteological correlates for inferring extra-oral structures reliably in dinosaurs? |url=https://d1wqtxts1xzle7.cloudfront.net/34675659/Thesis_final_document_6-18-2009-with-cover-page-v2.pdf?Expires=1657936600&Signature=AiYeKQRvlcgeqwXYRRA8WZgsMP8hk9CGfceU5eGq1FTmK9NwmO7H-3yvbObhslIoeDlqjoozkTroKCMw5nWnIIsSB66-9yhcKoeIcxw895JSVhSGq7~Yvu8ZYbeXwjoQ-oNJ0UVxAmTSqJByZybGalNNsZjxvO8CuX6Oy7cEjTVigp4PT5UzGbWDkt2HGRhwKmfttSckj75oKBa1g-DjHcVxJNWcbKDXfy-iqRbsy2PJyV3AlnptDwJpe4Nl7wHwTiaOTH0uI2kxSXw1jPeUxIP9Hcz-J1GbVNPxBkZPn0B3vTBwDNMWUEa-CUqXw8EQT6eHTiYBVT5xoFsI~DoMZw__&Key-Pair-Id=APKAJLOHF5GGSLRBV4ZA |access-date=July 15, 2022 }}{{Dead link|date=October 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref><ref>{{Cite journal |last1=Milinkovitch |first1=Michel C. |last2=Manukyan |first2=Liana |last3=Debry |first3=Adrien |last4=Di-Poï |first4=Nicolas |last5=Martin |first5=Samuel |last6=Singh |first6=Daljit |last7=Lambert |first7=Dominique |last8=Zwicker |first8=Matthias |date=2013-01-04 |title=Crocodile Head Scales Are Not Developmental Units But Emerge from Physical Cracking |journal=Science |language=en |volume=339 |issue=6115 |pages=78–81 |doi=10.1126/science.1226265 |pmid=23196908 |bibcode=2013Sci...339...78M |s2cid=6859452 |issn=0036-8075|doi-access=free }}</ref><ref>{{Cite journal |last1=Hieronymus |first1=Tobin L. |last2=Witmer |first2=Lawrence M. |last3=Tanke |first3=Darren H. |last4=Currie |first4=Philip J. |date=August 26, 2009 |title=The Facial Integument of Centrosaurine Ceratopsids: Morphological and Histological Correlates of Novel Skin Structures |journal=The Anatomical Record: Advances in Integrative Anatomy and Evolutionary Biology |language=en |volume=292 |issue=9 |pages=1370–1396 |doi=10.1002/ar.20985|pmid=19711467 |s2cid=13465548 |doi-access=free }}</ref>
===Body integument=== Long filamentous structures have been preserved along with skeletal remains of numerous coelurosaurs from the Early Cretaceous Yixian Formation and other nearby geological formations from Liaoning, China.<ref name=zhouetal2003>{{cite journal |last1=Zhou Zhonghe |author2=Barrett, Paul M.; & 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 |last3=Hilton |first3=Jason |s2cid=4412725 }}</ref> These filaments have usually been interpreted as "protofeathers," homologous with the branched feathers found in birds and some non-avian theropods,<ref name=chenetal1998>{{cite journal |last1=Chen Peiji |author2=Dong Zhiming |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|author-link2=Dong Zhiming |last3=Zhen |first3=Shuo-Nan |s2cid=4430927 |url=http://doc.rero.ch/record/14898/files/PAL_E2040.pdf }}</ref><ref name=xuetal2003>{{cite journal |last1=Xu Xing |author-link=Xu Xing (paleontologist) |author2=Zhou Zhonghe & Prum, 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 |last=Lingham-Soliar |first=Theagarten |author2=Feduccia, Alan |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|author-link2=Alan Feduccia }}</ref> A skeleton of ''Dilong paradoxus'' was described in 2004 that included the first example of feathers in a tyrannosauroid. Similarly to down feathers of modern birds, the feathers found in ''Dilong'' were branched but not pennaceous, and may have been used for insulation.<ref name=xuetal2004/> Even large tyrannosauroids have been found with evidence of feathers. ''Yutyrannus huali'', also from the Yixian Formation, is known from three specimens, each preserving traces of feathers on various parts of the body. While not all areas of the body preserve impressions across all three specimens, these fossils demonstrate that even in this medium-sized species, most of the body was covered in feathers.<ref name=yutyrannus>{{cite journal |last1=Xu |first1=X. |last2=Wang |first2=K. |last3=Zhang |first3=K. |last4=Ma |first4=Q. |last5=Xing |first5=L. |last6=Sullivan |first6=C. |last7= Hu |first7=D. |last8=Cheng |first8=S. |last9=Wang |first9=S. |display-authors=etal |year=2012 |title=A gigantic feathered dinosaur from the Lower Cretaceous of China |url=http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |journal=Nature |volume=484 |issue=7392 |pages=92–95 |doi=10.1038/nature10906 |pmid=22481363 |bibcode=2012Natur.484...92X |s2cid=29689629 |archive-url=https://web.archive.org/web/20120417134949/http://www.xinglida.net/pdf/Xu_et_al_2012_Yutyrannus.pdf |archive-date=2012-04-17 |df=dmy-all}}</ref>
The presence of feathers in basal tyrannosauroids is not surprising since they are now known to be characteristic of coelurosaurs, found in other basal genera like ''Sinosauropteryx'',<ref name=chenetal1998/> as well as all more derived groups.<ref name=zhouetal2003/> Rare fossilized skin impressions of some Late Cretaceous tyrannosaurids lack feathers, however, instead showing skin covered in fine, non-overlapping scales.<ref name=martinczerkas2000>{{cite journal |last=Martin |first=Larry D. |author-link=Larry Martin |author2=& Czerkas, Stephan A. |year=2000 |title=The fossil record of feather evolution in the Mesozoic |journal=American Zoologist |volume=40 |issue=4 |pages=687–694 |doi=10.1668/0003-1569(2000)040[0687:TFROFE]2.0.CO;2|citeseerx=10.1.1.505.6483 |s2cid=85701665 }}</ref> Possibly, feathers were present on other areas of the body: preserved skin impressions are very small and come primarily from the legs, pelvic region, and underside of the tail, which either lack feathers or only covered in a light down in some modern large ground-dwelling birds. Alternatively, secondary loss of feathers in large tyrannosaurids may be analogous with the similar loss of hair in the largest modern mammals like elephants, where a low surface area-to-volume ratio slows down heat transfer, making insulation by a coat of hair unnecessary or even detrimental.<ref name=xuetal2004/> A scientific publication by Phil Bell and colleagues in 2017 show that tyrannosaurids such as ''Gorgosaurus'', ''Tarbosaurus'', ''Albertosaurus'', ''Daspletosaurus'', and ''Tyrannosaurus'' had scales. The Bell et al. 2017 paper notes that the scale-like integument on bird feet were actually secondarily derived feathers according to paleontological and evolutionary developmental evidence so they hypothesize that the scaly skin preserved on some tyrannosaurid specimens might be secondarily derived from filamentous appendages like on Yutyrannus although strong evidence is needed to support this hypothesis.<ref>{{Cite journal|last1=Bell|first1=Phil R.|last2=Campione|first2=Nicolás E.|last3=Persons|first3=W. Scott|last4=Currie|first4=Philip J.|last5=Larson|first5=Peter L.|last6=Tanke|first6=Darren H.|last7=Bakker|first7=Robert T.|date=2017-06-30|title=Tyrannosauroid integument reveals conflicting patterns of gigantism and feather evolution|journal=Biology Letters|volume=13|issue=6|article-number=20170092|doi=10.1098/rsbl.2017.0092|pmc=5493735|pmid=28592520}}</ref><ref>{{Cite journal|last=Dhouailly|first=Danielle|date=2009|title=A new scenario for the evolutionary origin of hair, feather, and avian scales|journal=Journal of Anatomy|language=en|volume=214|issue=4|pages=587–606|doi=10.1111/j.1469-7580.2008.01041.x|issn=1469-7580|pmc=2736124|pmid=19422430}}</ref><ref>{{Cite journal|last1=Zheng|first1=Xiaoting|last2=Zhou|first2=Zhonghe|last3=Wang|first3=Xiaoli|last4=Zhang|first4=Fucheng|last5=Zhang|first5=Xiaomei|last6=Wang|first6=Yan|last7=Wei|first7=Guangjin|last8=Wang|first8=Shuo|last9=Xu|first9=Xing|date=2013-03-15|title=Hind Wings in Basal Birds and the Evolution of Leg Feathers|url=https://www.science.org/doi/abs/10.1126/science.1228753|journal=Science|volume=339|issue=6125|pages=1309–1312|doi=10.1126/science.1228753|pmid=23493711|bibcode=2013Sci...339.1309Z|s2cid=206544531|archive-date=2021-10-05|access-date=2021-10-05|archive-url=https://web.archive.org/web/20211005015925/https://www.science.org/doi/abs/10.1126/science.1228753|url-status=live|url-access=subscription}}</ref> However, other paleontologists argue that taphonomy is the possible cause of the lack of filamentous structures in tyrannosaurid fossils.<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=2022-09-20 |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>
===Head crests=== [[File:Guanlong wucaii.jpg|thumb|The elaborate head crest of ''Guanlong'', a basal tyrannosauroid from China.]] Bony crests are found on the skulls of many theropods, including numerous tyrannosauroids. The most elaborate is found in ''Guanlong'', where the nasal bones support a single, large crest which runs along the midline of the skull from front to back. This crest was penetrated by several large foramina (openings) which reduced its weight.<ref name=xuetal2006/> A less prominent crest is found in ''Dilong'', where low, parallel ridges run along each side of the skull, supported by the nasal and lacrimal bones. These ridges curve inwards and meet just behind the nostrils, making the crest ''Y''-shaped.<ref name=xuetal2004/> The fused nasals of tyrannosaurids are often very rough-textured. ''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 bone.<ref name=holtz2004/>
These head crests may have been used for display, perhaps for species recognition or courtship behavior.<ref name=holtz2004/> An example of the handicap principle may be the case of ''Guanlong'', where the large, delicate crest may have been a hindrance to hunting in what was presumably an active predator. If an individual was healthy and successful at hunting despite the fragile crest, it would indicate the superior quality of the individual over others with smaller crests. Similarly to the unwieldy tail of a male peacock or the outsized antlers of an Irish elk, the crest of ''Guanlong'' may have evolved via sexual selection, providing an advantage in courtship that outweighed any decrease in hunting ability.<ref name=xuetal2006/>
===Reproduction=== {{expand section|date=October 2020}} Neonate sized tyrannosaur fossils have been documented in the scientific literature.<ref name="tanke-brett-surman-2001">{{cite book |last1=Tanke |first1=Darren H. |last2=Brett-Surman |first2=Michael K. |year=2001 |chapter=Evidence of hatchling and nesting-size hadrosaurs (Reptilia: Ornithischia) from Dinosaur Provincial park (Dinosaur Park Formation: Campanian), Alberta |title=Mesozoic Vertebrate Life |editor1-last=Tanke |editor1-first=D. H. |editor2-last=Carpenter |editor2-first=Kenneth |pages=206–218 |location=Bloomington, IN |publisher=Indiana University Press |hdl=10088/8045 }}</ref>
==See also== * Specimens of Tyrannosaurus
==References== {{Reflist}}
==External links== *[http://theropoddatabase.com/Tyrannosauroidea.html List of tyrannosauroid specimens and species] at The Theropod Database.
{{Theropoda|C.}} {{Subject bar|Dinosaurs|auto=1}} {{Taxonbar|from=Q131396}}
Category:Tyrannosauroidea Category:Dinosaur superfamilies