Editing Tyrannosaurus (section)

==Paleoecology==
[[File:Hell Creek Formation Fauna.png|thumb|upright=1.4|left|Fauna of Hell Creek (''Tyrannosaurus'' in dark red, left).]]
''Tyrannosaurus'' lived during what is referred to as the [[Lancian]] faunal stage ([[Maastrichtian]] age) at the end of the Late Cretaceous. ''Tyrannosaurus'' ranged from [[Canada]] in the north to at least New Mexico in the south of [[Laramidia]].<ref name="larson2008" /> During this time ''[[Triceratops]]'' was the major herbivore in the northern portion of its range, while the [[titanosaurian]] [[Sauropoda|sauropod]] ''[[Alamosaurus]]'' "dominated" its southern range. ''Tyrannosaurus'' remains have been discovered in different ecosystems, including inland and coastal subtropical, and semi-arid plains.
[[File:Hell Creek dinosaurs and pterosaurs by durbed.jpg|thumb|''Tyrannosaurus'' and other animals of the Hell Creek Formation]]
Several notable ''Tyrannosaurus'' remains have been found in the [[Hell Creek Formation]]. During the Maastrichtian this area was [[subtropical]], with a warm and humid climate. The flora consisted mostly of [[angiosperms]], but also included trees like dawn redwood (''[[Metasequoia]]'').<ref>{{cite book |last1=Arens |first1=Nan Crystal |last2=Allen |first2=Sarah E. |title=Through the End of the Cretaceous in the Type Locality of the Hell Creek Formation in Montana and Adjacent Areas |chapter=A florule from the base of the Hell Creek Formation in the type area of eastern Montana: Implications for vegetation and climate |date=January 1, 2014 |doi=10.1130/2014.2503(06) |isbn=9780813725031 }}</ref> Archosaurs discovered from this formation include the [[ceratopsia]]ns ''[[Leptoceratops]]'', ''[[Torosaurus]]'', and ''[[Triceratops]]'',<ref>{{cite book|last=Ott|first=C.J.|year=2006|chapter=Cranial Anatomy and Biogeography of the First ''Leptoceratops gracilis'' (Dinosauria: Ornithischia) Specimens from the Hell Creek Formation, Southeast Montana|editor-last=Carpenter|editor-first=K.|title=Horns and Beaks: Ceratopsian and Ornithopod Dinosaurs|publisher=Indiana University Press|pages=213–234|isbn=0-253-34817-X}}</ref> the hadrosaurid ''[[Edmontosaurus annectens]]'',<ref>{{cite journal | last1 = Campione | first1 = N.E. | last2 = Evans | first2 = D.C. | year = 2011 | title = Cranial Growth and Variation in Edmontosaurs (Dinosauria: Hadrosauridae): Implications for Latest Cretaceous Megaherbivore Diversity in North America | journal = PLOS ONE | volume = 6 | issue = 9| page = e25186 | doi = 10.1371/journal.pone.0025186 | pmid = 21969872 | pmc=3182183| bibcode = 2011PLoSO...625186C | doi-access = free }}</ref> the [[Parksosauridae|parksosaurid]] ''[[Thescelosaurus]]'',<ref>{{cite book |last1=Weishampel |first1=D.B. |last2=Barrett |first2=P.M. |last3=Coria |first3=R.A. |last4=Le Loeufff |first4=J. |last5=Xu |first5=X. |last6=Zhao |first6=X. |last7=Sahni |first7=A. |last8=Gomani |first8=E.P.M. |last9=Noto |first9=C.R. |editor1-last=Weishampel |editor1-first=D.B. |editor2-last=Osmólska |editor2-first=H. |editor3-last=Dodson |editor3-first=P. |title=The Dinosauria |date=2004 |publisher=University of California Press |isbn=0-520-24209-2 |pages=517–606 |edition=2nd |chapter=Dinosaur Distribution}}</ref> the [[ankylosaur]]s ''[[Ankylosaurus]]'' and ''[[Denversaurus]]'',<ref>{{cite thesis|author=Bruns, M.E.|year=2015|title=Intraspecific variation in the armoured dinosaurs (Dinosauria: Ankylosauria)|publisher=University of Alberta Library|degree=PhD|doi=10.7939/R39K46485}}</ref> the [[pachycephalosaur]]s ''[[Pachycephalosaurus]]'' and ''[[Sphaerotholus]]'',<ref>{{Cite journal |last1=Woodruff |first1=D. Cary |last2=Schott |first2=Ryan K. |last3=Evans |first3=David C. |date=November 15, 2023 |title=Two new species of small-bodied pachycephalosaurine (Dinosauria, Marginocephalia) from the uppermost Cretaceous of North America suggest hidden diversity in well-sampled formations |journal=Papers in Palaeontology |language=en |volume=9 |issue=6 |at=e1535 |doi=10.1002/spp2.1535 |bibcode=2023PPal....9E1535W |issn=2056-2799}}</ref> the [[Paraves|paravian]] theropods ''[[Acheroraptor]]'' and ''[[Pectinodon]]'',<ref>{{cite journal|author1=Williamson, T.E.|author2=Brusatte, S.L.|year=2014|title=Small Theropod Teeth from the Late Cretaceous of the San Juan Basin, Northwestern New Mexico and Their Implications for Understanding Latest Cretaceous Dinosaur Evolution|journal=PLOS ONE|volume=9|issue=4|at=e93190|doi=10.1371/journal.pone.0093190|doi-access=free |pmid=24709990 |pmc=3977837 |bibcode=2014PLoSO...993190W }}</ref> other [[maniraptora]]n theropods ''[[Anzu wyliei|Anzu]]'', ''[[Eoneophron]]'', ''[[Trierarchuncus]]'' and indeterminate [[ornithomimid]]s,<ref>{{Cite journal|last1=Atkins-Weltman |first1=K. L. |last2=Simon |first2=D. J. |last3=Woodward |first3=H. N. |last4=Funston |first4=G. F. |last5=Snively |first5=E. |title=A new oviraptorosaur (Dinosauria: Theropoda) from the end-Maastrichtian Hell Creek Formation of North America |year=2024 |journal=PLOS ONE |volume=19 |issue=1 |at=e0294901 |doi=10.1371/journal.pone.0294901 |doi-access=free |pmid=38266012 |pmc=10807829 |bibcode=2024PLoSO..1994901A }}</ref><ref>{{cite journal |author1=Denver W. Fowler |author2=John P. Wilson |author3=Elizabeth A. Freedman Fowler |author4=Christopher R. Noto |author5=Daniel Anduza |author6=John R. Horner |year=2020 |title=''Trierarchuncus prairiensis'' gen. et sp. nov., the last alvarezsaurid: Hell Creek Formation (uppermost Maastrichtian), Montana |journal=Cretaceous Research |volume=116 |pages=Article 104560 |doi=10.1016/j.cretres.2020.104560 |s2cid=225630913 |doi-access=free |bibcode=2020CrRes.11604560F }}</ref> and the [[pterosaur]] ''[[Infernodrakon]]''.<ref>{{Cite journal |last1=Thomas |first1=Henry N. |last2=Hone |first2=David W. E. |last3=Gomes |first3=Timothy |last4=Peterson |first4=Joseph E. |date=February 28, 2025 |title=''Infernodrakon hastacollis'' gen. et sp. nov., a new azhdarchid pterosaur from the Hell Creek Formation of Montana, and the pterosaur diversity of Maastrichtian North America |journal=[[Journal of Vertebrate Paleontology]] |pages=e2442476 |doi=10.1080/02724634.2024.2442476 |issn=0272-4634}}</ref>

Another formation with ''Tyrannosaurus'' remains is the [[Lance Formation]] of Wyoming. This has been interpreted as a [[bayou]] environment similar to today's Gulf Coast. The fauna was very similar to Hell Creek, but with ''[[Struthiomimus]]'' replacing its relative ''Ornithomimus''. The small ceratopsian ''[[Leptoceratops]]'' also lived in the area.<ref>{{Cite book |title=The Dinosaurs of Wyoming |last=Derstler |first=K. |publisher=Wyoming Geological Association Guidebook, 44th Annual Field Conference. Wyoming Geological Association |year=1994 |editor-last=Nelson |editor-first=G. E. |pages=127–146 |chapter=Dinosaurs of the Lance Formation in eastern Wyoming}}</ref>

In its southern range, specifically based on remains discovered from the [[North Horn Formation]] of [[Utah]], ''Tyrannosaurus rex'' lived alongside the [[Titanosauria|titanosaur]] ''[[Alamosaurus]]'', the [[Ceratopsidae|ceratopsid]] ''[[Torosaurus]]'' and the indeterminate [[Troodontidae|troodontid]]s and [[Hadrosauridae|hadrosaurid]]s.<ref>{{cite journal |last1=Sampson |first1=Scott D. |last2=Loewon |first2=Mark A. |title=''Tyrannosaurus rex'' from the Upper Cretaceous (Maastrichtian) North Horn Formation of Utah: Biogeographic and Paleoecologic Implications |journal=Journal of Vertebrate Paleontology |date=June 27, 2005 |volume=25 |issue=2 |pages=469–472 |doi=10.1671/0272-4634(2005)025[0469:TRFTUC]2.0.CO;2 |jstor=4524461 |s2cid=131583311 |url=https://www.jstor.org/stable/4524461 |archive-date=March 15, 2024 |access-date=June 9, 2024 |archive-url=https://web.archive.org/web/20240315212717/https://www.jstor.org/stable/4524461 |url-status=live }}</ref><ref>{{cite book |last=Cifelli |first=Richard L. |author2=Nydam, Randall L. |author3=Eaton, Jeffrey G. |author4=Gardner, James D. |author5=Kirkland, James I. |year=1999 |title=Vertebrate Paleontology in Utah |chapter=Vertebrate faunas of the North Horn Formation (Upper Cretaceous–Lower Paleocene), Emery and Sanpete Counties, Utah |editor=Gillette, David D. |pages=377–388|publisher=Utah Geological Survey |location=Salt Lake City |isbn=1-55791-634-9}}</ref> ''Tyrannosaurus mcraeensis'' from the [[McRae Group]] of [[New Mexico]] coexisted with the [[Ceratopsidae|ceratopsid]] ''[[Sierraceratops]]'' and possibly the titanosaur ''Alamosaurus''.<ref name=T.mcraeensis/> Potential remains identified as cf. ''Tyrannosaurus'' have also been discovered from the [[Javelina Formation]] of [[Texas]],<ref name=T.mcraeensis/> where the remains of the titanosaur ''Alamosaurus'', the ceratopsid ''[[Bravoceratops]]'', the [[pterosaur]]s ''[[Quetzalcoatlus]]'' and ''[[Wellnhopterus]]'', and possible species of troodontids and hadrosaurids are found.<ref>{{cite journal |last1=Wick |first1=Steven L. |last2=Lehman |first2=Thomas M. |title=A new ceratopsian dinosaur from the Javelina Formation (Maastrichtian) of West Texas and implications for chasmosaurine phylogeny |journal=Naturwissenschaften |date=July 1, 2013 |volume=100 |issue=7 |pages=667–682 |doi=10.1007/s00114-013-1063-0 |pmid=23728202 |bibcode=2013NW....100..667W |s2cid=16048008 |url=https://pubmed.ncbi.nlm.nih.gov/23728202/ |access-date=November 27, 2020}}</ref><ref name="wellnhopterus">{{cite journal |first1=B. |last1=Andres |first2=W. Jr. |last2=Langston |title=Morphology and taxonomy of ''Quetzalcoatlus'' Lawson 1975 (Pterodactyloidea: Azhdarchoidea) |journal=Journal of Vertebrate Paleontology |year=2021 |volume=41 |issue=sup1 |page=142 |doi=10.1080/02724634.2021.1907587 |bibcode=2021JVPal..41S..46A |s2cid=245125409 |issn=0272-4634|doi-access=free }}</ref><ref>{{cite journal|last1=Tweet|first1=J.S.|last2=Santucci|first2=V.L.|year=2018|title=An Inventory of Non-Avian Dinosaurs from National Park Service Areas|journal=New Mexico Museum of Natural History and Science Bulletin|volume=79|pages=703–730|url=http://npshistory.com/publications/paleontology/nmmnhs-79-703.pdf|archive-date=November 2, 2024|access-date=June 9, 2024|archive-url=https://web.archive.org/web/20241102020100/https://npshistory.com/publications/paleontology/nmmnhs-79-703.pdf|url-status=live}}</ref> Its southern range is thought to have been dominated by semi-arid inland plains, following the probable retreat of the [[Western Interior Seaway]] as global sea levels fell.<ref>{{Cite journal |last1=Jasinski |first1=S. E. |last2=Sullivan |first2=R. M. |last3=Lucas |first3=S. G. |year=2011 |title=Taxonomic composition of the Alamo Wash local fauna from the Upper Cretaceous Ojo Alamo Formation (Naashoibito Member) San Juan Basin, New Mexico |journal=Bulletin |volume=53 |pages=216–271}}</ref>

''Tyrannosaurus'' may have also inhabited Mexico's [[Lomas Coloradas Formation]] in Sonora. Though skeletal evidence is lacking, six shed and broken teeth from the fossil bed have been thoroughly compared with other theropod genera and appear to be identical to those of ''Tyrannosaurus''. If true, the evidence indicates the range of ''Tyrannosaurus'' was possibly more extensive than previously believed.<ref>{{Cite journal |last1=Serrano-Brañas |first1=C. I. |last2=Torres-Rodrígueza |first2=E. |last3=Luna |first3=P. C. R. |last4=González |first4=I. |last5=González-León |first5=C. |year=2014 |title=Tyrannosaurid teeth from the Lomas Coloradas Formation, Cabullona Group (Upper Cretaceous) Sonora, México |journal=Cretaceous Research |volume=49 |pages=163–171 |doi=10.1016/j.cretres.2014.02.018|bibcode=2014CrRes..49..163S }}</ref> It is possible that tyrannosaurs were originally Asian species, migrating to North America before the end of the Cretaceous period.<ref>{{Cite journal |last1=Brusatte |first1=S. L. |last2=Carr |first2=T. D. |year=2016 |title=The phylogeny and evolutionary history of tyrannosauroid dinosaurs |journal=[[Scientific Reports]] |volume=6 |page=20252 |doi=10.1038/srep20252 |pmc=4735739 |pmid=26830019|bibcode=2016NatSR...620252B }}</ref>

===Population estimates===
[[File:Upper Cretaceous Hell Creek dinosaur census 2.svg|thumb|Chart of the time-averaged census for large-bodied dinosaurs from the entire Hell Creek Formation in the study area]]
According to studies published in 2021 by Charles Marshall et al., the total population of adult ''Tyrannosaurus'' at any given time was perhaps 20,000 individuals, with computer estimations also suggesting a total population no lower than 1,300 and no higher than 328,000. The authors themselves suggest that the estimate of 20,000 individuals is probably lower than what should be expected, especially when factoring in that disease pandemics could easily wipe out such a small population. Over the span of the genus' existence, it is estimated that there were about 127,000 generations and that this added up to a total of roughly 2.5 billion animals until their extinction.<ref name="nytimes2021"/><ref name="Marshall2021"/>

In the same paper, it is suggested that in a population of ''Tyrannosaurus'' adults numbering 20,000, the number of individuals living in an area the size of California could be as high as 3,800 animals, while an area the size of Washington D.C. could support a population of only two adult ''Tyrannosaurus''. The study does not take into account the number of juvenile animals in the genus present in this population estimate due to their occupation of a different niche than the adults, and thus it is likely the total population was much higher when accounting for this factor. Simultaneously, studies of living carnivores suggest that some predator populations are higher in density than others of similar weight (such as jaguars and hyenas, which are similar in weight but have vastly differing population densities). Lastly, the study suggests that in most cases, only one in 80 million ''Tyrannosaurus'' would become fossilized, while the chances were likely as high as one in every 16,000 of an individual becoming fossilized in areas that had more dense populations.<ref name="nytimes2021">{{Cite news|url=https://www.nytimes.com/2021/04/15/science/tyrannosaurus-rex-population.html |archive-url=https://ghostarchive.org/archive/20211228/https://www.nytimes.com/2021/04/15/science/tyrannosaurus-rex-population.html |archive-date=December 28, 2021 |url-access=limited|title=How Many Tyrannosaurus Rexes Ever Lived on Earth? Here's a New Clue.|first=Kenneth|last=Chang|newspaper=The New York Times|date=April 15, 2021}}{{cbignore}}</ref><ref name="Marshall2021">{{Cite journal|title=Absolute abundance and preservation rate of Tyrannosaurus rex|first1=Charles R.|last1=Marshall|first2=Daniel V.|last2=Latorre|first3=Connor J.|last3=Wilson|first4=Tanner M.|last4=Frank|first5=Katherine M.|last5=Magoulick|first6=Joshua B.|last6=Zimmt|first7=Ashley W.|last7=Poust|date=April 16, 2021|journal=Science|volume=372|issue=6539|pages=284–287|doi=10.1126/science.abc8300|pmid=33859033|bibcode=2021Sci...372..284M|doi-access=free}}</ref>

Meiri (2022) questioned the reliability of the estimates, citing uncertainty in metabolic rate, body size, sex and age-specific survival rates, habitat requirements and range size variability as shortcomings Marshall et al. did not take into account.<ref>{{Cite journal|last=Meiri|first=Shai|date=2022|title=Population sizes of T. rex cannot be precisely estimated|url=https://escholarship.org/uc/item/8mj4015f|journal=Frontiers of Biogeography|volume=14|issue=2|language=en|doi=10.21425/F5FBG53781|s2cid=245288933|doi-access=free|archive-date=February 4, 2022|access-date=February 8, 2022|archive-url=https://web.archive.org/web/20220204051249/https://escholarship.org/uc/item/8mj4015f|url-status=live}}</ref> The authors of the original publication replied that while they agree that their reported uncertainties were probably too small, their framework is flexible enough to accommodate uncerainty in physiology, and that their calculations do not depend on short-term changes in population density and geographic range, but rather on their long-term averages. Finally, they remark that they did estimate the range of reasonable survivorship curves and that they did include uncertainty in the time of onset of sexual maturity and in the growth curve by incorporating the
uncertainty in the maximum body mass.<ref>{{Cite journal|last1=Marshall|first1=Charles R.|last2=Latorre|first2=Daniel V.|last3=Wilson|first3=Connor J.|last4=Frank|first4=Tanner M.|last5=Magoulick|first5=Katherine M.|last6=Zimmt|first6=Joshua P.|last7=Poust|first7=Ashley W.|date=2022|title=With what precision can the population size of Tyrannosaurus rex be estimated? A reply to Meiri|url=https://escholarship.org/uc/item/8vv2g57c|journal=Frontiers of Biogeography|volume=14|issue=2|language=en|doi=10.21425/F5FBG55042|s2cid=245314491|doi-access=free|hdl=10852/101238|hdl-access=free|archive-date=January 21, 2022|access-date=February 8, 2022|archive-url=https://web.archive.org/web/20220121045413/https://escholarship.org/uc/item/8vv2g57c|url-status=live}} [[File:CC BY icon.svg|50px|class=noviewer]] Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License] {{Webarchive|url=https://web.archive.org/web/20171016050101/https://creativecommons.org/licenses/by/4.0/ |date=October 16, 2017 }}.</ref>