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'''''{{Infobox
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<br />{{Infobox
|Box title = Tyrannosaurus Rex
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|Box title = [[File:Tyrannoname.png]]
|image = Image:JW_T-Rex.png
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|image = File:Accurate_Rex.jpg|thumb
 
|Row 1 title = Suborder:
 
|Row 1 title = Suborder:
 
|Row 1 info = Therapoda
 
|Row 1 info = Therapoda
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|Row 3 title = Period:
 
|Row 3 title = Period:
 
|Row 3 info = Late Cretaceous (68-65 mya)
 
|Row 3 info = Late Cretaceous (68-65 mya)
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|Row 4 title = Length:|Row 4 info = 42-49 feet long(12.8-14.9 meters)|Row 5 title = Height:|Row 5 info = 15-21 feet tall (4.5-6.4 meters)|Row 6 title = Weight:|Row 6 info = 6.6-9 tonnes|caption = ''Accurate Tyrannosaurus''}}'''''Tyrannosaurus''''' (pronounced /tɨˌrænəˈsɔːrəs/ or /taɪˌrænoʊˈsɔːrəs/, meaning 'tyrant lizard') is a genus of [[wikipedia:Theropod|theropod]] dinosaur. The famous species '''''Tyrannosaurus rex''''' ('rex' meaning 'king' in Latin), commonly abbreviated to '''''T. rex''''', is a fixture in popular culture around the world, and is extensively used in scientific television and movies, such as documentaries and ''[[community:Jurassic Park|Jurassic Park]]'', and in children's series such as ''[[The Land Before Time]]''. ''Tyrannosaurus'' lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils of ''T. rex'' are found in a variety of [[wikipedia:geologic formation|rock formations]] dating to the last three million years of the [[wikipedia:Cretaceous|Cretaceous Period]], approximately 68 to 65&nbsp;million years ago; it was among the last non-[[wikipedia:aves|avian]] dinosaurs to exist prior to the [[wikipedia:Cretaceous–Tertiary extinction event|Cretaceous–Tertiary extinction event]].
|Row 4 title = Length:|Row 4 info = 42-49 feet long(12.8-14.9 meters)|Row 5 title = Height:|Row 5 info = 15-21 feet tall (4.6-6.4 meters)|Row 6 title = Weight:|Row 6 info = 6.6-9 tonnes|caption = ''Tyrannosaurus'' as it appeared in ''Jurassic World''}}'''''
 
'''''Tyrannosaurus Rex '''''meaning "king tyrant lizard" (Greek ''tyrannos'' = tyrant + ''sauros'' = lizard + ''rex'' = king), also known and simply as '''''T. rex''''', was a large carnivorous'' ''[[Theropoda|theropod]] [[dinosaur]] that lived'' ''from 68-66 million years ago. ''Tyrannosaurus'' is the most-known- and famous dinosaur that has ever lived. Its [[fossil]] remains are relatively rare, as of 2012 only 44 specimens had been found,'' ''including three complete skulls. ''Tyrannosaurus rex'' measures from 37 to 43 feet (11.2–13.1 meters) long stands 13 feet (3.9 m) tall at hips, and weighs between 7 and 9 tons (14,000-18,000&nbsp;lb), meaning this dinosaur was even bigger than the average African Elephant, and by far one of the largest carnivores ever in North America.
 
   
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Like other tyrannosaurids, ''Tyrannosaurus'' was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, ''Tyrannosaurus'' forelimbs were small, though unusually powerful for their size, and bore two primary digits, along with a possible third [[wikipedia:vestigial|vestigial]] digit. Although other theropods rivaled or exceeded ''T. rex'' in [[wikipedia:dinosaur size|size]], it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 13 metres (43 ft.) in length,<ref name="brochu2003">Brochu, Christopher A. and Richard A. Ketcham ''Osteology of Tyrannosaurus Rex: Insights from a Nearly Complete Skeleton and High-resolution Computed Tomographic Analysis of the Skull''. 2003, Society of Vertebrate Paleontology, in Northbrook, Illinois.</ref> up to 4 metres (13 ft.) tall at the hips,<ref name=SueFMNH/> and up to 6.8 metric tonnes (7.5 short tons) in weight.<ref name=ericksonetal2004>Erickson, Gregory M., Makovicky, Peter J.; [[wikipedia:Phil Currie|Currie, Philip J.]]; Norell, Mark A.; Yerby, Scott A.; & Brochu, Christopher A., 2004. ''Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs'', from the Journal of Nature, vol. 430, issue 7001, pp. 772–775.</ref> By far the largest carnivore in its environment, ''T. rex'' may have been an [[wikipedia:Apex predator|apex predator]], preying upon [[hadrosaur]]s and [[Wikipedia:Ceratopsians|ceratopsians,]] although some experts have suggested it was primarily a scavenger.
[[File:Outrun-t-rex-orig.jpg|thumb|left|King of The Dinosaurs]]What's more is it's speculated that dinosaurs grew their whole lives, so its possible we'll find even bigger specimens in the near future. It lived throughout what is now western North America, with a much wider range than most other [[Tyrannosauridae|tyrannosaurids]], including the states of Wyoming, Montana, North and South Dakota, Colorado, Canada, and even Texas. It was among the last non-[[Aves|avian]] dinosaurs to exist prior to the [[Cretaceous–Tertiary extinction event|Cretaceous–Tertiary&nbsp;<span id="cke_bm_70S" style="display: none;">&nbsp;</span><span style="display: none;">&nbsp;</span><span id="cke_bm_72S" style="display: none;">&nbsp;</span><span style="display: none;">&nbsp;</span>]][[Extinction]] Event.''' '''While ''Tyrannosaurus'' and its relatives ruled the north, abelisaurs such as ''[[Carnotaurus]]'' ruled the south. In fact, the tyrannosaurids were so successful, that whenever a tyrannosaur moved into an area anywhere within the northern hemisphere, all other large theropods were soon wiped out due to being in direct competition with them. So people have speculated about whether there may be more than one type of tyrannosaur in ''T.rex''<nowiki/><nowiki>'s environment.</nowiki>
 
   
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More than 30&nbsp;specimens of ''T. rex'' have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and [[wikipedia:biomechanics|biomechanics]]. The feeding habits, physiology and potential speed of ''T. rex'' are a few subjects of debate. Its [[wikipedia:Taxonomy|taxonomy]] is also controversial, with some scientists considering ''[[wikipedia:Tarbosaurus|Tarbosaurus bataar]]'' from Asia to represent a second species of ''Tyrannosaurus'' and others maintaining ''Tarbosaurus'' as a separate genus. Several other genera of North American tyrannosaurids have also been [[wikipedia:synonym (biology)|synonymized]] with ''Tyrannosaurus''.
''[[File:Tyrannosaurus rex by teratophoneus-d9bnkd0.png|thumb|250px|Size comparision between Tyrannosaurus and human]]''
 
 
[[Tyrannosaurus Chicks]]
''Tyrannosaurus rex ''is one of the most most well-known dinosaurs, ranging from toys to television shows. Its name still brings fear even today, and it's also celebrate<span style="font-size:14px;">d as the "King of the Dinosaurs". It has become the quintessential dinosaur/monster, and an icon in dinosaur culture. </span><span style="font-size:14px;">In 1892, </span>[[Edward Drinker Cope|Edward Cope]]<span style="font-size:14px;"> described the f</span><span style="font-size:14px;">irst known </span>''Tyrannosaurus rex''<span style="font-size:14px;"> skeleton as </span>''Manospondylus gigas''<span style="font-size:14px;">, </span><span style="font-size:14px;">but this is now considered a </span>''Nomen oblitum''<span style="font-size:14px;">. Barnum Brown's 1902 discovery of "</span>''Dynamosaurus imperiosus''<span style="font-size:14px;">," is also now called </span>''Tyrannosaurus rex''<span style="font-size:14px;">, </span>''<nowiki>Tyrannosaurus'</nowiki>''<span style="font-size:14px;"> type species. He found two more specimens, in 1902 and 1905. </span>''[[Tarbosaurus]]''<span style="font-size:14px;"> was at one point considered to be a second Asian species of </span>''Tyrannosaurus''<span style="font-size:14px;">, but, despite similarities between the two, Tarbosaurus is now usually referred to as it's own species, Tarbosaurus bataar</span>
 
 
==Description==
 
[[Image:Tyrannosaurusscale.png|thumb|right|200px|Various specimens of ''Tyrannosaurus rex'' with a human for scale.]]
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[[Image:Theropodscalewithhuman.png|thumb|right|200px|Size comparison of selected giant theropod dinosaurs, with ''Tyrannosaurus'' in purple.]]
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''Tyrannosaurus rex'' was one of the largest land carnivores of all time; the largest complete specimen, [[wikipedia:Field Museum of Natural History|FMNH]] PR2081 ("[[wikipedia:Sue (dinosaur)|Sue]]"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13 ft) tall at the hips.<ref name=SueFMNH>[http://www.fieldmuseum.org/sue/about_vital.asp Sue's vital statistics] Sue at the Field Museum. [[Wikipedia:Field Museum of Natural History|Field Museum of Natural History.]]</ref> Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons),<ref name=henderson1999>Henderson, DM, 1999. ''Estimating the masses and centers of mass of extinct animals by 3-D mathematical slicing'', from the Journal of Paleobiology, vol. 25, issue 1, pp. 88–106 [http://paleobiol.geoscienceworld.org/cgi/content/abstract/25/1/88].</ref> to less than 4.5 metric tons (5.0 short tons),<ref name=andersonetal1985>Anderson, JF and Hall-Martin AJ, [[wikipedia:Dale Russell|Russell, Dale A.]] 1985. ''Long bone circumference and weight in mammals, birds and dinosaurs'', from the Journal of Zoology, vol. 207, issue 1, pp. 53–61.</ref><ref name=bakker1986>Bakker, Robert T., 1986. ''The Dinosaur Heresies''. New York, Kensington Publishing, ISBN 0-688-04287-2</ref> with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons).<ref name=farlowetal1995>Farlow, James O., Smith MB, & Robinson, JM, 1995. Body mass, bone "strength indicator", and cursorial potential of ''Tyrannosaurus rex'', from the Journal of Vertebrate Paleontology, vol. 15, issue 4, pp. 713–725. [http://www.vertpaleo.org/publications/jvp/15-713-725.cfm]</ref><ref name=seebacher2001>Seebacher, Frank. 2001. ''A new method to calculate allometric length-mass relationships of dinosaurs'', from the Journal of Vertebrate Paleontology, vol. 21, issue 1, pp. 51–60.</ref><ref name=christiansenfarina2004>Christiansen, Per & Fariña, Richard A., 2004. ''Mass prediction in theropod dinosaurs'', from the Journal of Historical Biology, vol. 16, issues 2-4, pp. 85–92.</ref><ref name=ericksonetal2004>Erickson, Gregory M., Makovicky, Peter J.; [[wikipedia:Phil Currie|Currie, Philip J.]]; Norell, Mark A.; Yerby, Scott A.; & Brochu, Christopher A. 2004. ''Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs'', from the Journal of Nature, vol. 430, issue 7001, pp. 772–775.</ref> Although ''Tyrannosaurus rex'' was larger than the well known Jurassic theropod ''[[Allosaurus]]'', it was slightly smaller than Cretaceous carnivores ''[[Spinosaurus]]'' and ''[[Giganotosaurus]]''.<ref name=dalsassoetal2005>dal Sasso, Cristiano and Maganuco, Simone; Buffetaut, Eric; & Mendez, Marcos A. 2005. New information on the skull of the enigmatic theropod ''Spinosaurus'', with remarks on its sizes and affinities, from the Journal of Vertebrate Paleontology vol. 25, issue 4, pp. 888–896. [http://www.bioone.org/perlserv/?request=get-abstract&doi=10.1671%2F0272-4634%282005%29025%5B0888%3ANIOTSO%5D2.0.CO%3B2]</ref><ref name=calvocoria1998>Calvo, Jorge O., and Rodolfo Coria, 1998, December. New specimen of ''Giganotosaurus carolinii'' (Coria & Salgado, 1995), supports it as the as the largest theropod ever found, from the Journal of Gaia Revista de Geociências, vol. 15, pp. 117–122. [http://www.mnhn.ul.pt/geologia/gaia/7.pdf]</ref>
   
 
The neck of ''T. rex'' formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs were long thought to bear only two digits, but there is an unpublished report of a third, vestigial digit in one specimen.<ref name=quinlanetal2007/> In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.<ref name="brochu2003"/>
[[File:638px-T-rex ve triceratops.svg.png|thumb|left]]
 
   
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[[File:Tyrannosaurus.gif|thumb|258px]]The largest known ''T. rex'' skulls measure up to 5 feet (1.5 m) in length.<ref>[http://www.montana.edu/cpa/news/nwview.php?article=3607 Museum unveils world's largest T-rex skull] (2006-04-07) Montana State University.</ref> Large ''fenestrae'' (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects ''Tyrannosaurus''’ skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good [[wikipedia:Binocular vision|binocular vision]].<ref name="Stevens2006Binocular">Stevens, Kent A. 2006, June. ''Binocular vision in theropod dinosaurs'', from the Journal of Vertebrate Paleontology, vol. 26, issue 2, pp. 321–330. [http://www.webcitation.org/query?id=1256480784253462&url=www.geocities.com/Athens/Bridge/4602/theropod_binocularvision.pdf]</ref><ref name=jaffe>Jaffe, Eric (2006-07-01). Sight for 'Saur Eyes: ''T. rex'' vision was among nature's best, from the Journal of Science , vol. 170, issue 1, page 3. [http://www.sciencenews.org/view/generic/id/7500/title/Sight_for_Saur_Eyes_%3Ci%3ET._rex%3Ci%3E_vision_was_among_natures_best]</ref> The skull bones were massive and the [[wikipedia:nasal bone|nasals]] and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids.<ref name="SnivelyHendersonPhillips2006FusedVaultedNasals">2006, ''Fused and vaulted nasals of tyrannosaurid dinosaurs: Implications for cranial strength and feeding mechanics'', from the Acta Palaeontologica Polonica, vol. 51, issue 3, pp. 435–454. Eric Snively, Donald M. Henderson, and Doug S. Phillips. [http://www.app.pan.pl/archive/published/app51/app51-435.pdf]</ref><ref name=GEetal96>Erickson, G.M. Van Kirk, S.D.; Su, J.; Levenston, M.E.; Caler, W.E.; and Carter, D.R. 1996. Bite-force estimation for ''Tyrannosaurus rex'' from tooth-marked bones, from the Journal of Nature, vol. 382, pp. 706–708.</ref><ref name=MM03>Meers, M.B., August, 2003. [http://www.ingentaconnect.com/content/tandf/ghbi/2003/00000016/00000001/art00001 Maximum bite force and prey size of ''Tyrannosaurus rex'' and their relationships to the inference of feeding behavior,] from the journal of Historical Biology: A Journal of Paleobiology, vol. 16, issue 1, pp. 1–12.</ref> The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.<ref name="holtz1994" /><ref name="paul1988" />
''Tyrannosaurus rex ''was not the undisputed biggest carnivorous dinosaur, however. ''[[Spinosaurus]]'' may have been the biggest carnivore ever discovered, with the largest estimates being 52 feet (15.8 m), long though its habits indicate a more aquatic than terrestrial lifestyle, similar to those of crocodilians, and it's only based on fragments for the time being, so its exact size isn't truly known, but ''Tyrannosaurus'' was by far the biggest carnivore ever in North America. Three carnosaurs called [[Mapusaurus]], ''[[Giganotosaurus]]'' and ''[[Carcharodontosaurus]]'' also compete against ''T. rex'' for the title of largest carnivorous dinosaur, but recent study on body structure shows that due to excessive body mass, the tyrant lizard was likely heavier than either contenders.
 
   
 
[[Image:T rex restoration.jpg|thumb|Life restoration of a ''Tyrannosaurus rex''.]]
'''''<nowiki/>'''''
 
[[File:Ls shutterstock 105146921 free.jpg|thumb|330x330px]]
 
==Description==
 
[[File:Tyrannosaurusscale.png|thumb|Various specimens of ''Tyrannosaurus rex'' with a human for scale.]]
 
''Tyrannosaurus rex'' was one of the largest land carnivores of all time; the largest complete specimen, [[wikipedia:Field Museum of Natural History|FMNH]] PR2081 ("[[wikipedia:Sue (dinosaur)|Sue]]"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13 ft) tall at the hips. Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons), to less than 4.5 metric tons (5.0 short tons), with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons). Although ''Tyrannosaurus rex'' was larger than the well known Jurassic theropod ''[[Allosaurus]]'', it was slightly smaller than Cretaceous carnivores ''[[Spinosaurus]]'' and ''[[Giganotosaurus]]''.
 
   
 
The teeth of ''T. rex'' displayed marked [[wikipedia:Heterodont|heterodonty]] (differences in shape).<ref name="Smith2005HeterodontyTRex">Smith, J.B. Heterodonty in ''Tyrannosaurus rex'': implications for the taxonomic and systematic utility of theropod dentitions, from the Journal of Vertebrate Paleontology, vol. 25, issue 4, pp. 865–887. December, 2005. [http://www.webcitation.org/query?id=1256456620451304&url=www.geocities.com/Athens/Bridge/4602/trexteeth.pdf]</ref><ref name="brochu2003">Brochu C.R., 2003. Osteology of ''Tyrannosaurus rex'': insights from a nearly complete skeleton and high-resolution computed tomographic analysis of the skull, from the journal of Society of Vertebrate Paleontology Memoirs, vol. 7, pp. 1–138.</ref> The [[Wikipedia:Premaxilla|premaxillary]] teeth at the front of the upper jaw were closely packed, D-shaped in cross-section, had reinforcing ridges on the rear surface, were [[wikipedia:Incisor|incisiform]] (their tips were chisel-like blades) and curved backwards. The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when ''Tyrannosaurus'' bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers; more widely spaced and also had reinforcing ridges.<ref name="New Scientist1998DinosaurDetectives">''The dinosaur detectives,'' 1998, fromt the Journal of New Scientist. Douglas K, Young S. [http://www.newscientist.com/channel/life/dinosaurs/mg15821305.300] "One palaeontologist memorably described the huge, curved teeth of T. rex as 'lethal bananas'".</ref> Those in the upper jaw were larger than those in all but the rear of the lower jaw. The largest found so far is estimated to have been 30 centimetres (12 in) long including the root when the large reptile was alive, making it the largest tooth of any carnivorous dinosaur.<ref name=SueFMNH/>
The neck of ''T. rex'' formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs were long thought to bear only two digits, but there is an unpublished report of a third, vestigial digit in one specimen. In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.
 
   
 
==Paleobiology==
The largest known ''T. rex'' skulls measure up to 5 feet (1.5 m) in length. Large ''fenestrae'' (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects ''Tyrannosaurus''’ skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good [[wikipedia:Binocular vision|binocular vision]]. The skull bones were massive and the [[wikipedia:nasal bone|nasals]] and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids. The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.
 
 
===Life history===
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[[Image:T-rex graph.png|thumb|300px|right|A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids. ''Tyrannosaurus rex'' is drawn in black. Based on Erickson et al. 2004.]]
 
The identification of several specimens as juvenile ''Tyrannosaurus rex'' has allowed scientists to document [[wikipedia:ontogeny|ontogenetic]] changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual ([[wikipedia:Los Angeles County Museum of Natural History|LACM]] 28471, the "Jordan theropod") is estimated to have weighed only 29.9&nbsp;kg (66&nbsp;lb), while the largest, such as [[Wikipedia:Field Museum of Natural History|FMNH]] PR2081 ("[[wikipedia:Sue (dinosaur)|Sue]]") most likely weighed over 5400&nbsp;kg (6&nbsp;short tons). [[wikipedia:Histology|Histologic]] analysis of ''T. rex'' bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.<ref name="ericksonetal2004">Erickson, G.M., Makovicky, P.J., Currie, P.J., Norell, M.A., Yerby, S.A. & Brochu, C.A. 2004. Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs. ''Nature'' 430: 772–775.</ref>
   
 
Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A ''T. rex'' growth curve is S-shaped, with juveniles remaining under 1800&nbsp;kg (2&nbsp;short tons) 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 600&nbsp;kg (1,300&nbsp;lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600&nbsp;kg (1,300&nbsp;lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen ([[wikipedia:Royal Tyrrell Museum of Palaeontology|RTMP]] 81.12.1).<ref name="ericksonetal2004"/> Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age.<ref name="hornerpadian2004">Horner JR, Padian K. ''Age and growth dynamics of Tyrannosaurus rex'', from the journal of Proceedings. Biological sciences / the Royal Society, vol. 271, issue 1551, pp. 1875–1880. 2004, September. [http://journals.royalsociety.org/openurl.asp?genre=article&issn=0962-8452&volume=271&issue=1551&spage=1875]</ref> This sudden change in growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old ''T. rex'' from Montana ([[wikipedia:Museum of the Rockies|MOR]] 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age.<ref name="schweitzeretal2005">Schweitzer MH, Wittmeyer JL, Horner JR. ''Gender-specific reproductive tissue in ratites and Tyrannosaurus rex'', from the Journal of Science (New York, N.Y.), vol. 308, issue 5727, pages 1456–1460. June, 2005, [http://www.sciencemag.org/cgi/pmidlookup?view=long&pmid=15933198].</ref> Further study indicates an age of 18 for this specimen.<ref name=LW08>Lee, Andrew H. and Werning, Sarah, 2008. ''Sexual maturity in growing dinosaurs does not fit reptilian growth models'', from the Journal of Proceedings of the National Academy of Sciences, vol. 105, issue 2, pp. 582–587.</ref> Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.<ref name="ericksonetal2006">Erickson GM, Currie PJ, Inouye BD, Winn AA. ''Tyrannosaur life tables: an example of nonavian dinosaur population biology'', from the Journal of Science (New York, N.Y.), vol. 313, issue 5784, pp. 213–7. 2006, July.</ref>
The teeth of ''T. rex'' displayed marked [[wikipedia:Heterodont|heterodonty]] (differences in shape). The [[Wikipedia:Premaxilla|premaxillary]] teeth at the front of the upper jaw were closely packed, D-shaped in cross-section, had reinforcing ridges on the rear surface, were [[wikipedia:Incisor|incisiform]] (their tips were chisel-like blades) and curved backwards. The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when ''Tyrannosaurus'' bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers; more widely spaced and also had reinforcing ridges. Those in the upper jaw were larger than those in all but the rear of the lower jaw. The largest found so far is estimated to have been 30 centimetres (12 in) long including the root when the animal was alive, making it the largest tooth of any carnivorous dinosaur.
 
   
 
Over half of the known ''T. rex'' specimens appear to have died within six years of reaching sexual maturity, a pattern which 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. One study suggests that the rarity of juvenile ''T. rex'' fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the [[wikipedia:Fossil record|fossil record]] or to the bias of fossil collectors towards larger, more spectacular specimens.<ref name="ericksonetal2006"/>
==Classification==
 
''Tyrannosaurus'' is the [[wikipedia:Biological type|type]] genus of the superfamily [[wikipedia:Tyrannosauroidea|Tyrannosauroidea]], the [[wikipedia:Family (biology)|family]] [[wikipedia:Tyrannosauridae|Tyrannosauridae]], and the subfamily Tyrannosaurinae; in other words it is the standard by which paleontologists decide whether to include other species in the same group. Other members of the tyrannosaurine subfamily include the North American ''[[Daspletosaurus]]'' and the Asian ''[[Tarbosaurus]]'', both of which have occasionally been synonymized with ''Tyrannosaurus''. Tyrannosaurids were once commonly thought to be descendants of earlier large theropods such as [[wikipedia:Spinosauroidea|megalosaurs]] and [[wikipedia:Carnosauria|carnosaurs]], although more recently they were reclassified with the generally smaller [[wikipedia:Coelurosauria|coelurosaurs]].
 
   
 
===Posture===
[[Image:Tyrannoskull.jpg|thumb|Profile view of a ''Tyrannosaurus'' skull (AMNH 5027).]]
 
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{| align="right" | cellspacing="0" | cellpadding="0"
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|- valign="top"
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|[[Image:Outdated Trex Posture.jpg|thumb|200px|right|Outdated reconstruction (by [[Wikipedia:Charles R. Knight|Charles R. Knight]]), showing 'tripod' pose.]]
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|[[Image:Updated Trex posture.jpg|thumb|200px|right|Replica at [[wikipedia:Senckenberg Museum|Senckenberg Museum]], showing modern view of posture.]]
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|}
 
Like many bipedal dinosaurs, ''Tyrannosaurus rex'' was historically depicted as a 'living tripod', with the body at 45 degrees or less from the vertical and the tail dragging along the ground, similar to a kangaroo. This concept dates from [[wikipedia:Joseph Leidy|Joseph Leidy]]'s 1865 reconstruction of ''[[wikipedia:Hadrosaurus|Hadrosaurus]]'', the first to depict a dinosaur in a bipedal posture.<ref name="leidy1865">Leidy, J, 1865. ''Memoir on the extinct reptiles of the Cretaceous formations of the United States'', from the journal of Smithsonian Contributions to Knowledge, vol. 14, pp. 1–135.</ref> [[wikipedia:Henry Fairfield Osbourn|Henry Fairfield Osborn]], former president of the [[wikipedia:American Museum of Natural History|American Museum of Natural History]] (AMNH) in New York City, who believed the creature stood upright, further reinforced the notion after unveiling the first complete ''T. rex'' skeleton in 1915. It stood in this upright pose for nearly a century, until it was dismantled in 1992.<ref name="amnhsite">[http://www.amnh.org/exhibitions/expeditions/treasure_fossil/Treasures/Tyrannosaurus/tyrannos.html?dinos Tyrannosaurus,] from the American Museum of Natural History. Retrieved on January 25th, 2009.</ref> By 1970, scientists realized this pose was incorrect and could not have been maintained by a living animal, as it would have resulted in the [[wikipedia:dislocation (medicine)|dislocation]] or weakening of several joints, including the hips and the articulation between the head and the [[wikipedia:spinal column|spinal column]].<ref name="newman1970">Newman, BH, 1970. "Stance and gait in the flesh-eating ''Tyrannosaurus''", from the Biological Journal of the Linnean Society, vol. 2, pp. 119–123.</ref> The inaccurate AMNH mount inspired similar depictions in many films and paintings (such as [[wikipedia:Rudolph F. Zallinger|Rudolph Zallinger]]'s famous mural ''The Age Of Reptiles'' in [[wikipedia:Yale University|Yale University]]'s [[wikipedia:Peabody Musuem of Natural History|Peabody Museum of Natural History]])<ref>[http://www.yale.edu/peabody/explore/reptiles.html The Age of Reptiles Mural], 2008, from Yale University.</ref> until the 1990s, when films such as ''[[wikipedia:Jurassic Park (film)|Jurassic Park]]'' introduced a more accurate posture to the general public. Modern representations in museums, art, and film show ''T. rex'' with its body approximately parallel to the ground and tail extended behind the body to balance the head.<ref name="paul1988"/>
   
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===Arms===
In 1955, Soviet paleontologist [[wikipedia:Evgeny Maleev|Evgeny Maleev]] named a new species, ''Tyrannosaurus bataar'', from Mongolia. By 1965, this species had been renamed ''Tarbosaurus bataar''. Despite the renaming, many [[wikipedia:phylogeny|phylogenetic]] analyses have found ''Tarbosaurus bataar'' to be the [[wikipedia:sister taxon|sister taxon]] of ''Tyrannosaurus rex'', and it has often been considered an Asian species of ''Tyrannosaurus''. A recent redescription of the skull of ''Tarbosaurus bataar'' has shown that it was much narrower than that of ''Tyrannosaurus rex'' and that during a bite, the distribution of stress in the skull would have been very different, closer to that of ''[[wikipedia:Alioramus|Alioramus]]'', another Asian tyrannosaur. A related [[wikipedia:Clade|cladistic]] analysis found that ''Alioramus'', not ''Tyrannosaurus'', was the sister taxon of ''Tarbosaurus'', which, if true, would suggest that ''Tarbosaurus'' and ''Tyrannosaurus'' should remain separate.
 
  +
[[Image:T rex arm.jpg|thumb|right|300px|Closeup of forelimb; specimen at [[Wikipedia:National Museum of Natural History|National Museum of Natural History]], Washington, DC.]]
 
When ''Tyrannosaurus rex'' was first discovered, the humerus was the only element of the forelimb known.<ref name="osborn1905">Osborn, H. F., 1905. ''Tyrannosaurus and other Cretaceous carnivorous dinosaurs'', from the Journal of the Bulletin of the AMNH, vol. 21, issue 14, pp. 259–265. Published by the American Museum of Natural History, in New York City. [http://hdl.handle.net/2246/1464].</ref> For the initial mounted skeleton as seen by the public in 1915, Osborn substituted longer, three-fingered forelimbs like those of ''[[Allosaurus]]''.<ref name="osborn1917"/> However, a year earlier, [[wikipedia:Lawrence Lambe|Lawrence Lambe]] described the short, two-fingered forelimbs of the closely related ''[[wikipedia:Gorgosaurus|Gorgosaurus]]''.<ref name="lambe1914">Lambe, L. M., 1914. "On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of the skull of ''Stephanosaurus marginatus'' from the same horizon", from the Journal of the Ottawa Naturalist, vol. 27, pp. 129–135.</ref> This strongly suggested that ''T. rex'' had similar forelimbs, but this hypothesis was not confirmed until the first complete ''T. rex'' forelimbs were identified in 1989, belonging to MOR 555 (the "Wankel rex").<ref name="hornerlessem1993"/> The remains of "Sue" also include complete forelimbs.<ref name="brochu2003"/> ''T. rex'' arms are very small relative to overall body size, measuring only 1 metre (3.3 ft) long. However, they are not [[wikipedia:vestigial organ|vestigial]] but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation.<ref name="osborn1906">Osborn, Henry Fairfield and Barnum Brown, 1906. ''Tyrannosaurus, Upper Cretaceous carnivorous dinosaur'', from the Journal of the Bulletin of the AMNH, vol. 22, issue 16, pp. 281–296. Published by the American Museum of Natural History, in New York City. [http://hdl.handle.net/2246/1473].</ref> It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position.<ref name="newman1970"/> Another possibility is that the forelimbs held struggling prey while it was dispatched by the tyrannosaur's enormous jaws. This hypothesis may be supported by [[wikipedia:biomechanics|biomechanical]] analysis. ''T. rex'' forelimb bones exhibit extremely thick [[wikipedia:Bone#Structure|cortical bone]], indicating that they were developed to withstand heavy loads. The [[wikipedia:biceps brachii|biceps brachii]] muscle of a full-grown ''Tyrannosaurus rex'' was capable of lifting 199 kilograms (439 lb) by itself; this number would only increase with other muscles (like the [[wikipedia:brachialis|brachialis]]) acting in concert with the biceps. A ''T. rex'' forearm also had a reduced range of motion, with the shoulder and elbow joints allowing only 40 and 45 degrees of motion, respectively. In contrast, the same two joints in ''[[wikipedia:Deinonychus|Deinonychus]]'' allow up to 88 and 130 degrees of motion, respectively, while a human arm can rotate 360 degrees at the shoulder and move through 165 degrees at the elbow. The heavy build of the arm bones, extreme strength of the muscles, and limited range of motion may indicate a system designed to hold fast despite the stresses of a struggling prey animal.<ref name="carpentersmith2001">Kenneth Carpenter & Matt Smith. Edited by [[wikipedia:Darren Tanke|Darren Tanke]] and Kenneth Carpenter. ''Mesozoic vertebrate life'', published by the Indiana University Press in Bloomington, 2001. Pages 90–116. ISBN 0-253-33907-3 Chapter: Forelimb Osteology and Biomechanics of ''Tyrannosaurus rex''.</ref>
   
 
===Soft tissue===
Other tyrannosaurid fossils found in the same formations as ''T. rex'' were originally classified as separate taxa, including ''Aublysodon'' and ''Albertosaurus megagracilis'', the latter being named ''Dinotyrannus megagracilis'' in 1995. However, these fossils are now universally considered to belong to juvenile ''T. rex''. A small but nearly complete skull from Montana, 60 centimetres (2.0 ft) long, may be an exception. This skull was originally classified as a species of ''[[Gorgosaurus]]'' (''G. lancensis'') by [[wikipedia:Charles W. Gilmore|Charles W. Gilmore]] in 1946, but was later referred to a new genus, ''[[Nanotyrannus]]''. Opinions remain divided on the validity of ''N. lancensis''. Many paleontologists consider the skull to belong to a juvenile ''T. rex''. There are minor differences between the two species, including the higher number of teeth in ''N. lancensis'', which lead some scientists to recommend keeping the two genera separate until further research or discoveries clarify the situation.
 
 
In the March 2005 issue of ''[[wikipedia:Science (journal)|Science]]'', [[wikipedia:Mary Higby Schweitzer|Mary Higby Schweitzer]] of [[wikipedia:North Carolina State University|North Carolina State University]] and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone, from a 68-million-year-old ''Tyrannosaurus''. The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue.<ref name=smithsonian-fields>''Dinosaur Shocker'', by Fields, Helen. From the Journal of ''Smithsonian Magazine'', May, 2006. [http://www.smithsonianmag.com/science-nature/10021606.html].</ref> Designated as the Museum of the Rockies specimen 1125, or MOR 1125, the dinosaur was previously excavated from the [[wikipedia:Hell Creek Formation|Hell Creek Formation]]. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The structures bear resemblance to ostrich blood cells and vessels. Whether an unknown process, distinct from normal fossilization, preserved the material, or the material is original, the researchers do not know, and they are careful not to make any claims about preservation.<ref name=MHSetalb>Mary H. Schweitzer, Jennifer L. Wittmeyer, John R. Horner and Jan K. Toporski. ''Soft-tissue vessels and cellular preservation in Tyrannosaurus rex'' from the Journal of ''Science'', vol. 307, issue 5717, pp. 1952–5. March, 2005. [http://www.sciencemag.org/cgi/content/abstract/307/5717/1952].</ref> If it is found to be original material, any surviving proteins may be used as a means of indirectly guessing some of the DNA content of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of previous finds may merely be the result of people assuming preserved tissue was impossible, therefore simply not looking. Since the first, two more tyrannosaurs and a hadrosaur have also been found to have such tissue-like structures.<ref name=smithsonian-fields/> Research on some of the tissues involved has suggested that birds are closer relatives to tyrannosaurs than other modern animals.<ref>Paul Rincon, ''Protein links T. rex to chickens'' [http://news.bbc.co.uk/2/hi/science/nature/6548719.stm] from BBC News. (2007-04-12).</ref>
   
 
In studies reported in the journal ''Science'' in April 2007, Asara and colleagues concluded that seven traces of collagen proteins detected in purified ''T. rex'' bone most closely match those reported in chickens, followed by frogs and newts. The discovery of proteins from a creature tens of millions of years old, along with similar traces the team found in a mastodon bone at least 160,000 years old, upends the conventional view of fossils and may shift paleontologists' focus from bone hunting to biochemistry. Until these finds, most scientists presumed that fossilization replaced all living tissue with inert minerals. Paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies, called the finds "a milestone", and suggested that dinosaurs could "enter the field of molecular biology and really slingshot paleontology into the modern world."<ref>Dan Vergano, ''Yesterday's T. Rex is today's chicken''. [http://www.usatoday.com/tech/science/discoveries/2007-04-12-trex-protein_N.htm]. ''USA Today'' (2007-04-13).</ref>
===''Manospondylus''===
 
[[Image:Trex skull.gif|thumb|right|Skull of ''T. rex'', type specimen at the [[wikipedia:Cernegie Museum of Natural History|Carnegie Museum of Natural History]]. This was heavily and inaccurately restored with plaster using ''[[Allosaurus]]'' as a model, and has since been disassembled.]]
 
The first fossil specimen which can be attributed to ''Tyrannosaurus rex'' consists of two partial vertebrae (one of which has been lost) found by [[wikipedia:Edward Drinker Cope|Edward Drinker Cope]] in 1892 and described as ''Manospondylus gigas''. Osborn recognized the similarity between ''M. gigas'' and ''T. rex'' as early as 1917 but, due to the fragmentary nature of the ''Manospondylus'' vertebrae, he could not synonymize them conclusively.
 
   
 
Subsequent studies in April 2008 confirmed the close connection of ''T. rex'' to modern birds. Postdoctoral biology researcher Chris Organ at [[wikipedia:Harvard University|Harvard University]] announced, "With more data, they would probably be able to place ''T. rex'' on the evolutionary tree between alligators and chickens and ostriches." Co-author John M. Asara added, "We also show that it groups better with birds than modern reptiles, such as alligators and [[wikipedia:anole lizard|green anole lizards]]."<ref>Randolph E. Schmid, ''Associated Press''. ''Scientists study evidence modern birds came from dinosaurs'', [http://www.newsvine.com/_news/2008/04/24/1450460-scientists-study-evidence-modern-birds-came-from-dinosaurs], from ''Newsvine''. (2008-04-24).</ref>
In June 2000, the [[wikipedia:Black Hills Institute|Black Hills Institute]] located the type locality of ''M. gigas'' in South Dakota and unearthed more tyrannosaur bones there. These were judged to represent further remains of the same individual, and to be identical to those of ''T. rex''. According to the rules of the [[wikipedia:International Code of Zoological Nomenclature|International Code of Zoological Nomenclature]] (ICZN), the system that governs the scientific naming of animals, ''Manospondylus gigas'' should therefore have priority over ''Tyrannosaurus rex'', because it was named first. However, the Fourth Edition of the ICZN, which took effect on 1 January 2000, states that "the prevailing usage must be maintained" when "the senior synonym or homonym has not been used as a valid name after 1899" and "the junior synonym or homonym has been used for a particular taxon, as its presumed valid name, in at least 25 works, published by at least 10 authors in the immediately preceding 50 years..." ''Tyrannosaurus rex'' may qualify as the valid name under these conditions and would most likely be considered a ''nomen protectum'' ("protected name") under the ICZN if it was ever challenged, which it has not yet been. ''Manospondylus gigas'' would then be deemed a ''nomen oblitum'' ("forgotten name").
 
   
 
The presumed soft tissue was called into question by Thomas Kaye of the [[wikipedia:Universiy of Washington|University of Washington]] and his co-authors in 2008. They contend that what was really inside the tyrannosaur bone was slimy [[wikipedia:Biofilm|biofilm]] created by bacteria that coated the voids once occupied by blood vessels and cells.<ref>2008, July. ''Dinosaurian Soft Tissues Interpreted as Bacterial Biofilms'', from the Journal of PLoS ONE, vol. 3, issue 7, pp. e2808. By Thomas G. Kaye, Gary Gaugler, and Zbigniew Sawlowicz.</ref> The researchers found that what previously had been identified as remnants of blood cells, because of the presence of iron, were actually framboids; microscopic mineral spheres bearing iron. They found similar spheres in a variety of other fossils from various periods, including an [[wikipedia:ammonite|ammonite]]. In the ammonite they found the spheres in a place where the iron they contain could not have had any relationship to the presence of blood.<ref>''New Research Challenges Notion That Dinosaur Soft Tissues Still Survive''. Published by Newswise, (2008-07-24) [http://newswise.com/articles/view/542898/].</ref>
==Paleobiology==
 
===Life history===
 
The identification of several specimens as juvenile ''Tyrannosaurus rex'' has allowed scientists to document [[wikipedia:ontogeny|ontogenetic]] changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual ([[wikipedia:Los Angeles County Museum of Natural History|LACM]] 28471, the "Jordan theropod") is estimated to have weighed only 29.9&nbsp;kg (66&nbsp;lb), while the largest, such as [[Wikipedia:Field Museum of Natural History|FMNH]] PR2081 ("[[wikipedia:Sue (dinosaur)|Sue]]") most likely weighed over 5400&nbsp;kg (6&nbsp;short tons). [[wikipedia:Histology|Histologic]] analysis of ''T. rex'' bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.
 
   
 
===Skin and feathers===
Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A ''T. rex'' growth curve is S-shaped, with juveniles remaining under 1800&nbsp;kg (2&nbsp;short tons) 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 600&nbsp;kg (1,300&nbsp;lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600&nbsp;kg (1,300&nbsp;lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen ([[wikipedia:Royal Tyrrell Museum of Palaeontology|RTMP]] 81.12.1). Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age. This sudden change in growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old ''T. rex'' from Montana ([[wikipedia:Museum of the Rockies|MOR]] 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age. Further study indicates an age of 18 for this specimen. Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.
 
  +
In 2004, the scientific journal ''[[wikipedia:Nature (journal)|Nature]]'' published a report describing an early tyrannosauroid, ''[[wikipedia:Dilong paradoxus|Dilong paradoxus]]'', from the famous [[wikipedia:Yixian Formation|Yixian Formation]] of China. As with many other theropods discovered in the Yixian, the fossil skeleton was preserved with a coat of filamentous structures which are commonly recognized as the precursors of feathers. It has also been proposed that ''Tyrannosaurus'' and other closely related tyrannosaurids had such protofeathers. However, rare skin impressions from adult tyrannosaurids in Canada and Mongolia show pebbly scales typical of other dinosaurs.<ref>[http://www.dinosauria.com/jdp/trex/skin.htm Tyrannosaur Skin Impression Found In Alberta.] (1996-03-25). D. Tanke.</ref> While it is possible that protofeathers existed on parts of the body which have not been preserved, a lack of [[wikipedia:thermal insulation|insulatory]] body covering is consistent with modern multi-ton mammals such as elephants, hippopotamus, and most species of rhinoceros. As an object increases in size, its ability to retain heat increases due to its decreasing surface area-to-volume ratio. Therefore, as large animals evolve in or [[wikipedia:Biological dispersal#Dispersal in animals|disperse]] into warm climates, a coat of fur or feathers loses its [[wikipedia:natural selection|selective]] advantage for thermal insulation and can instead become a disadvantage, as the insulation traps excess heat inside the body, possibly overheating the animal. Protofeathers may also have been secondarily lost during the evolution of large tyrannosaurids like ''Tyrannosaurus'', especially in warm Cretaceous climates.<ref name="xuetal2004">Xing Xu, Mark A. Norell, Xuewen Kuang, Xiaolin Wang, Qi Zhao and Chengkai Jia. ''Basal tyrannosauroids from China and evidence for protofeathers in tyrannosauroids'', from the Journal of Nature, vol. 431, issue 7009, pp. 680–684 (2004-10-07).</ref>
   
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===Thermoregulation===
Over half of the known ''T. rex'' specimens appear to have died within six years of reaching sexual maturity, a pattern which 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. One study suggests that the rarity of juvenile ''T. rex'' fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the [[wikipedia:Fossil record|fossil record]] or to the bias of fossil collectors towards larger, more spectacular specimens.
 
  +
''Tyrannosaurus'', like most dinosaurs, was long thought to have an ectothermic ("cold-blooded") reptilian metabolism. The idea of dinosaur ectothermy was challenged by scientists like [[wikipedia:Robert T. Bakker|Robert T. Bakker]] and [[wikipedia:John Ostrom|John Ostrom]] in the early years of the "[[wikipedia:Dinosaur Renaissance|Dinosaur Renaissance]]", beginning in the late 1960s.<ref name="bakker1968">Bakker, Robert T. 1968, ''The superiority of dinosaurs'', from the Journal of ''Discovery'', vol. 3, issue 2, pp. 11–12 [http://bio.fsu.edu/~amarquez/Evolutionary%20Morphology%20fall%202004/Bakker/Bakker%201968%20-%20Superiority%20of%20DInos.pdf]</ref><ref name="bakker1972">Robert T. Bakker, 1972. ''Anatomical and ecological evidence of endothermy in dinosaurs'', from the Journal of Nature, vol. 238, pp. 81–85. [http://bio.fsu.edu/~amarquez/Evolutionary%20Morphology%20fall%202004/Bakker/14-%20Bakker%201972%20-%20dino%20endothermy.pdf].</ref> ''Tyrannosaurus rex'' itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle.<ref name="bakker1986"/> Since then, several paleontologists have sought to determine the ability of ''Tyrannosaurus'' to [[wikipedia: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 [[wikipedia:Indeterminate growth|indeterminate growth]] seen in most other vertebrates.<ref name="hornerpadian2004"/>
   
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Oxygen isotope ratios in fossilized bone are sometimes used to determine the temperature at which the bone was deposited, as the ratio between certain isotopes correlates with temperature. In one specimen, the isotope ratios in bones from different parts of the body indicated a temperature difference of no more than 4 to 5°C (7 to 9°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 [[wikipedia:geochemistry|geochemist]] William Showers to indicate that ''T. rex'' maintained a constant internal body temperature ([[wikipedia:Homeotherm|homeothermy]]) and that it enjoyed a metabolism somewhere between ectothermic reptiles and endothermic mammals.<ref name="barrettshowers1994">Reese E. Barrick & William J. Showers. ''Thermophysiology of Tyrannosaurus rex: Evidence from Oxygen Isotopes'', from the Journal of Science, in New York City, vol. 265, issue 5169, pp. 222–224. 1994, July. [http://www.sciencemag.org/cgi/content/abstract/265/5169/222].</ref> Other scientists have pointed out that the ratio of oxygen isotopes in the fossils today does not necessarily represent the same ratio in the distant past, and may have been altered during or after fossilization (diagenesis).<ref name="truemanetal2003">Clive Trueman, Carolyn Chenery, David A. Eberth and Baruch Spiro, 2003. ''Diagenetic effects on the oxygen isotope composition of bones of dinosaurs and other vertebrates recovered from terrestrial and marine sediments'', from the Journal of the Geological Society, vol. 160, issue 6, page 895.</ref> Barrick and Showers have defended their conclusions in subsequent papers, finding similar results in another theropod dinosaur from a different continent and tens of millions of years earlier in time (''[[Giganotosaurus]]'').<ref name="barrickshowers1999">Barrick, Reese E. & William J. Showers, October 1999. "Thermophysiology and biology of ''Giganotosaurus'': comparison with ''Tyrannosaurus''", from the Journal of ''Palaeontologia Electronica'', vol. 2, issue 2, [http://palaeo-electronica.org/1999_2/gigan/issue2_99.htm].</ref> [[wikipedia:Ornithischia|Ornithischian]] dinosaurs also showed evidence of homeothermy, while [[wikipedia:varanidae|varanid]] lizards from the same formation did not.<ref name="barrickstevens1997">James O. Farlow and M. K. Brett-Surman, ''The Complete Dinosaur'', published by the Indiana University Press in Bloomington, 1999. pp. 474–490. ISBN 0-253-21313-4 Chapter: Oxygen isotopes in dinosaur bones. By Reese E. Barrick, Michael K. Stoskopf, and William J. Showers.</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 [[wikipedia:Gigantothermy|gigantothermy]], as in some living sea turtles.<ref name="paladinoetal1997">James O. Farlow and M. K. Brett-Surman, ''The Complete Dinosaur'', published by Indiana University Press in Bloomington, 1999. pp. 491–504. ISBN 0-253-21313-4 Chapter: A blueprint for giants: modeling the physiology of large dinosaurs, by Frank V. Paladino, James R. Spotila and Peter Dodson.</ref><ref name="chinsamyhillenius2004">David B. Weishampel, Peter Dodson and Halszka Osmólska ''The dinosauria'' University of California Press, in Berkeley, 2004. pp. 643–659. ISBN 0-520-24209-2 Chapter: Physiology of nonavian dinosaurs, by Anusuya Chinsamy, and Willem J. Hillenius.</ref>
===Sexual dimorphism===
 
[[Image:Courting Trex fossils.jpg|thumb|''Tyrannosaurus'' skeleton casts mounted in a mating position, Jurassic Museum of Asturias.]]
 
As the number of specimens increased, scientists began to analyze the variation between individuals and discovered what appeared to be two distinct body types, or ''morphs'', similar to some other theropod species. As one of these morphs was more solidly built, it was termed the 'robust' morph while the other was termed '[[Wikt:gracile|gracile]].' Several [[wikipedia:morphology (biology)|morphological]] differences associated with the two morphs were used to analyze [[wikipedia:Sexual dimorphism|sexual dimorphism]] in ''Tyrannosaurus rex'', with the 'robust' morph usually suggested to be female. For example, the pelvis of several 'robust' specimens seemed to be wider, perhaps to allow the passage of [[wikipedia:Egg (biology)|eggs]]. It was also thought that the 'robust' morphology correlated with a reduced [[wikipedia:chevron (anatomy)|chevron]] on the first tail vertebra, also ostensibly to allow eggs to pass out of the [[wikipedia:reproductive system|reproductive tract]], as had been erroneously reported for crocodiles.
 
   
  +
===Footprints===
In recent years, evidence for sexual dimorphism has been weakened. A 2005 study reported that previous claims of sexual dimorphism in crocodile chevron anatomy were in error, casting doubt on the existence of similar dimorphism between ''T. rex'' genders. A full-sized chevron was discovered on the first tail vertebra of "Sue," an extremely robust individual, indicating that this feature could not be used to differentiate the two morphs anyway. As ''T. rex'' specimens have been found from Saskatchewan to New Mexico, differences between individuals may be indicative of geographic variation rather than sexual dimorphism. The differences could also be age-related, with 'robust' individuals being older animals.
 
  +
[[Image:New Mexico Trex Footprint.jpg|200px|right|thumb|The probable ''Tyrannosaurus rex'' footprint from New Mexico.]]
  +
Two isolated fossilized footprints have been tentatively assigned to ''Tyrannosaurus rex''. The first was discovered at [[wikipedia:Philmont Scout Ranch|Philmont Scout Ranch]], New Mexico, in 1983 by American geologist Charles Pillmore. Originally thought to belong to a [[hadrosaurid]], examination of the footprint revealed a large 'heel' unknown in [[wikipedia:ornithopod|ornithopod]] dinosaur tracks, and traces of what may have been a hallux, the dewclaw-like fourth digit of the tyrannosaur foot. The footprint was published as the [[wikipedia:ichnogenus|ichnogenus]] ''Tyrannosauripus pillmorei'' in 1994, by Martin Lockley and Adrian Hunt. Lockley and Hunt suggested that it was very likely the track was made by a ''Tyrannosaurus rex'', which would make it the first known footprint from this species. The track was made in what was once a vegetated wetland mud flat. It measures 83 centimetres (33 in) long by 71 centimetres (28 in) wide.<ref name="lockley&hunt1994">Lockley, MG and Hunt, AP, 1994. "A track of the giant theropod dinosaur ''Tyrannosaurus'' from close to the Cretaceous/Tertiary boundary, northern New Mexico", from the Journal of ''Ichnos'', vol. 3, pp. 213-218.</ref>
   
  +
A second footprint that may have been made by a ''Tyrannosaurus'' was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana. This second track measures 76 centimetres (30 in) long, shorter than the track described by Lockley and Hunt. Whether or not the track was made by ''Tyrannosaurus'' is unclear, though ''Tyrannosaurus'' and ''Nanotyrannus'' are the only large theropods known to have existed in the Hell Creek Formation. Further study of the track (a full description has not yet been published) will compare the Montana track with the one found in New Mexico.<ref name="rextrack2007">[http://www.nhm.ac.uk/about-us/news/2007/october/news_12515.html T.rex footprint discovered.] (2007). Published by the [http://www.nhm.ac.uk/index.html Natural History Museum.]</ref>
Only a single ''T. rex'' specimen has been conclusively shown to belong to a specific gender. Examination of "B-rex" demonstrated the preservation of soft tissue within several bones. Some of this tissue has been identified as medullary tissue, a specialized tissue grown only in modern birds as a source of calcium for the production of eggshell during ovulation. As only female birds lay eggs, medullary tissue is only found naturally in females, although males are capable of producing it when injected with female reproductive hormones like estrogen. This strongly suggests that "B-rex" was female, and that she died during ovulation.<ref name="schweitzeretal2005"/> Recent research has shown that medullary tissue is never found in crocodiles, which are thought to be the closest living relatives of dinosaurs, aside from birds. The shared presence of medullary tissue in birds and theropod dinosaurs is further evidence of the close evolutionary relationship between the two.
 
   
===Posture===
+
===Locomotion===
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[[Image:Sauropod tracks.png|thumb|right|A sequence of [[sauropod]] footprints. No such sequence has yet been reported for tyrannosaurs, making gait and speed estimates difficult.|link=Special:FilePath/Sauropod_tracks.png]]
Like many bipedal dinosaurs, ''Tyrannosaurus rex'' was historically depicted as a 'living tripod', with the body at 45 degrees or less from the vertical and the tail dragging along the ground, similar to a kangaroo. This concept dates from [[wikipedia:Joseph Leidy|Joseph Leidy]]'s 1865 reconstruction of ''[[wikipedia:Hadrosaurus|Hadrosaurus]]'', the first to depict a dinosaur in a bipedal posture. [[wikipedia:Henry Fairfield Osbourn|Henry Fairfield Osborn]], former president of the [[wikipedia:American Museum of Natural History|American Museum of Natural History]] (AMNH) in New York City, who believed the creature stood upright, further reinforced the notion after unveiling the first complete ''T. rex'' skeleton in 1915. It stood in this upright pose for nearly a century, until it was dismantled in 1992. By 1970, scientists realized this pose was incorrect and could not have been maintained by a living animal, as it would have resulted in the [[wikipedia:dislocation (medicine)|dislocation]] or weakening of several joints, including the hips and the articulation between the head and the [[wikipedia:spinal column|spinal column]]. The inaccurate AMNH mount inspired similar depictions in many films and paintings (such as [[wikipedia:Rudolph F. Zallinger|Rudolph Zallinger]]'s famous mural ''The Age Of Reptiles'' in [[wikipedia:Yale University|Yale University]]'s [[wikipedia:Peabody Musuem of Natural History|Peabody Museum of Natural History]]) until the 1990s, when films such as ''[[wikipedia:Jurassic Park (film)|Jurassic Park]]'' introduced a more accurate posture to the general public. Modern representations in museums, art, and film show ''T. rex'' with its body approximately parallel to the ground and tail extended behind the body to balance the head.
 
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[[Image:T.rex. Hind foot.jpg|thumb|Foot of a ''Tyrannosaurus rex''.|link=Special:FilePath/T.rex._Hind_foot.jpg]]
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There are two main issues concerning the locomotory abilities of ''Tyrannosaurus'': how well it could turn; and what its maximum straight-line speed was likely to have been. Both are relevant to the debate about whether it was a hunter or a scavenger (see below).
   
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''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>Hutchinson JR, Ng-Thow-Hing V, Anderson FC. ''A 3D interactive method for estimating body segmental parameters in animals: application to the turning and running performance of Tyrannosaurus rex'', from the Journal of theoretical biology, vol. 246, issue 4, pp. 660–80. 2007, June.</ref> The cause of the difficulty is [[wikipedia:rotational inertia|rotational inertia]], since much of ''Tyrannosaurus''’ mass was some distance from its center of gravity, like a human carrying a heavy timber—although it might have reduced the average distance by arching its back and tail and pulling its head and forelimbs close to its body, rather like the way ice skaters pull their arms closer in order to spin faster.<ref name="CarrierWalterLee2000TurningPerformance">''Influence of rotational inertia on turning performance of theropod dinosaurs: clues from humans with increased rotational inertia'', from the [[wikipedia:Journal of Experimental Biology|Journal of Experimental Biology,]] vol. 204, issue 22, pp. 3917–3926. Published by the Company of Biologists, [http://jeb.biologists.org/cgi/content/full/204/22/3917]. Written by David R. Carrier, Rebecca M. Walter and David V. Lee (2001-11-15).</ref>
===Arms===
 
When ''Tyrannosaurus rex'' was first discovered, the humerus was the only element of the forelimb known. For the initial mounted skeleton as seen by the public in 1915, Osborn substituted longer, three-fingered forelimbs like those of ''[[Allosaurus]]''. However, a year earlier, [[wikipedia:Lawrence Lambe|Lawrence Lambe]] described the short, two-fingered forelimbs of the closely related ''[[Gorgosaurus]]''. This strongly suggested that ''T. rex'' had similar forelimbs, but this hypothesis was not confirmed until the first complete ''T. rex'' forelimbs were identified in 1989, belonging to MOR 555 (the "Wankel rex"). The remains of "Sue" also include complete forelimbs. ''T. rex'' arms are very small relative to overall body size, measuring only 1 metre (3.3 ft) long. However, they are not [[wikipedia:vestigial organ|vestigial]] but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation. It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position. Another possibility is that the forelimbs held struggling prey while it was dispatched by the tyrannosaur's enormous jaws. This hypothesis may be supported by [[wikipedia:biomechanics|biomechanical]] analysis. ''T. rex'' forelimb bones exhibit extremely thick [[wikipedia:Bone#Structure|cortical bone]], indicating that they were developed to withstand heavy loads. The [[wikipedia:biceps brachii|biceps brachii]] muscle of a full-grown ''Tyrannosaurus rex'' was capable of lifting 199 kilograms (439 lb) by itself; this number would only increase with other muscles (like the [[wikipedia:brachialis|brachialis]]) acting in concert with the biceps. A ''T. rex'' forearm also had a reduced range of motion, with the shoulder and elbow joints allowing only 40 and 45 degrees of motion, respectively. In contrast, the same two joints in ''[[Deinonychus]]'' allow up to 88 and 130 degrees of motion, respectively, while a human arm can rotate 360 degrees at the shoulder and move through 165 degrees at the elbow. The heavy build of the arm bones, extreme strength of the muscles, and limited range of motion may indicate a system designed to hold fast despite the stresses of a struggling prey animal.
 
   
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Scientists have produced a wide range of maximum speed estimates, mostly around 11 metres per second (25 mph), but a few as low as 5–11 metres per second (11–25 mph), and a few as high as 20 metres per second (45 mph). Researchers have to rely on various estimating techniques because, while there are many [[wikipedia: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>Hutchinson, J.R., ''Biomechanical Modeling and Sensitivity Analysis of Bipedal Running Ability. II. Extinct Taxa'', from the Journal of Morphology, vol. 262, issue 1, pp. 441–461. 2004. [http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf].</ref> Scientists who think that ''Tyrannosaurus'' was able to run point out that hollow bones and other features that would have lightened its body may have kept adult weight to a mere 5&nbsp;tons or so, or that other animals like ostriches and horses with long, flexible legs are able to achieve high speeds through slower but longer strides. Additionally, some have argued that ''Tyrannosaurus'' had relatively larger leg muscles than any animal alive today, which could have enabled fast running 40–70 kilometres per hour (25–43 mph).<ref name="HutchinsonGarcia2002TrexSlow">Hutchinson JR, Garcia M, ''Tyrannosaurus was not a fast runner'', from the Journal of Nature, vol. 415, issue 6875, pp. 1018–21. 2002, February.</ref>
===Soft tissue===
 
In the March 2005 issue of ''[[wikipedia:Science (journal)|Science]]'', [[wikipedia:Mary Higby Schweitzer|Mary Higby Schweitzer]] of [[wikipedia:North Carolina State University|North Carolina State University]] and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone, from a 68-million-year-old ''Tyrannosaurus''. The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue. Designated as the Museum of the Rockies specimen 1125, or MOR 1125, the dinosaur was previously excavated from the [[wikipedia:Hell Creek Formation|Hell Creek Formation]]. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The structures bear resemblance to ostrich blood cells and vessels. Whether an unknown process, distinct from normal fossilization, preserved the material, or the material is original, the researchers do not know, and they are careful not to make any claims about preservation. If it is found to be original material, any surviving proteins may be used as a means of indirectly guessing some of the DNA content of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of previous finds may merely be the result of people assuming preserved tissue was impossible, therefore simply not looking. Since the first, two more tyrannosaurs and a hadrosaur have also been found to have such tissue-like structures.<ref name=smithsonian-fields/> Research on some of the tissues involved has suggested that birds are closer relatives to tyrannosaurs than other modern animals.
 
   
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Jack Horner and Don Lessem argued in 1993 that ''Tyrannosaurus'' was slow and probably could not run (no airborne phase in mid-stride), because its ratio of femur (thigh bone) to tibia (shin bone) length was greater than 1, as in most large theropods and like a modern elephant.<ref name="hornerlessem1993" /> However, Holtz (1998) noted that tyrannosaurids and some closely related groups had significantly longer [[wikipedia:distal|distal]] hindlimb components (shin plus foot plus toes) relative to the femur length than most other theropods), and that tyrannosaurids and their close relatives had a tightly interlocked [[wikipedia:Metatarsus|metatarsus]] that more effectively transmitted locomotory forces from the foot to the lower leg than in earlier theropods ("metatarsus" means the foot bones, which function as part of the leg in [[wikipedia:digitigrade|digitigrade]] animals). He therefore concluded that tyrannosaurids and their close relatives were the fastest large theropods.<ref name="Holtz1998TaxonomyCoelurosauria">Thomas R. Holtz, ''Phylogenetic taxonomy of the Coelurosauria (Dinosauria; Theropoda)'', from the Journal of Paleontology, (1996-05-01), vol. 70, issue 3, pp. 536–538. [http://jpaleontol.geoscienceworld.org/cgi/content/abstract/70/3/536].</ref>
In studies reported in the journal ''Science'' in April 2007, Asara and colleagues concluded that seven traces of collagen proteins detected in purified ''T. rex'' bone most closely match those reported in chickens, followed by frogs and newts. The discovery of proteins from a creature tens of millions of years old, along with similar traces the team found in a mastodon bone at least 160,000 years old, upends the conventional view of fossils and may shift paleontologists' focus from bone hunting to biochemistry. Until these finds, most scientists presumed that fossilization replaced all living tissue with inert minerals. Paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies, called the finds "a milestone", and suggested that dinosaurs could "enter the field of molecular biology and really slingshot paleontology into the modern world."
 
   
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[[Image:T-rex Leg Bone structures.png|thumb|200px|left|Skeletal anatomy of a ''T. rex'' right leg.]]
Subsequent studies in April 2008 confirmed the close connection of ''T. rex'' to modern birds. Postdoctoral biology researcher Chris Organ at [[wikipedia:Harvard University|Harvard University]] announced, "With more data, they would probably be able to place ''T. rex'' on the evolutionary tree between alligators and chickens and ostriches." Co-author John M. Asara added, "We also show that it groups better with birds than modern reptiles, such as alligators and [[wikipedia:anole lizard|green anole lizards]].
 
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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 11 metres per second (25 mph), which is about the speed of a human sprinter. But he also noted that such estimates depend on many dubious assumptions.<ref name="Christiansen1998Strength">Christiansen, P., ''Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential'', from the Journal of ''Gaia'', (1998), vol. 15, pp. 241–255. [http://www.mnhn.ul.pt/geologia/gaia/19.pdf]. ISSN 0871-5424</ref>
   
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Farlow and colleagues (1995) have argued that a 6 short tons (5.4 t) to 8 short tons (7.3 t) ''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&nbsp;meters/s²) and its tiny arms could not have reduced the impact.<ref name="farlowetal1995"/><ref>[http://www.newscientist.com/article/mg14819982.600-the-bigger-they-come-the-harder-they-fall.html The bigger they come, the harder they fall.] J. Hecht. (1995-10-05). Published by NewScientist; page 18.</ref> However, giraffes have been known to gallop at 50 kilometres per hour (31 mph), 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>[http://www.wildlifesafari.info/giraffe.html Giraffe.] WildlifeSafari.info.</ref><ref>[http://www.zoo.org/zoo_info/history/chapters/history4.html The History of Woodland Park Zoo - Chapter 4.]</ref> Thus it is quite possible that ''Tyrannosaurus'' also moved fast when necessary and had to accept such risks.<ref name="Alexander2006DinoBioMechanics">Alexander, R.M., ''Dinosaur biomechanics'', from the journal of Proc Biol Sci., (August 7 2006), vol. 273, issue 1596, pp. 1849–1855. Published by The Royal Society.</ref><ref name="Hanna2002MultipleInjuriesBigAl">Hanna, Rebecca R., 2002. ''Multiple injury and infection in a sub-adult theropod dinosaur (''Allosaurus fragilis'') with comparisons to allosaur pathology in the Cleveland-Lloyd dinosaur quarry collection'', from the Journal of Vertebrate Paleontology, vol. 22, issue 1, pp. 76–90. (catalogs the injuries of the ''[[Allosaurus]]'' known as "[[wikipedia:The Ballad of Big Al|Big Al]]" - at least one was attributed to a fall.)</ref>
The presumed soft tissue was called into question by Thomas Kaye of the [[wikipedia:Universiy of Washington|University of Washington]] and his co-authors in 2008. They contend that what was really inside the tyrannosaur bone was slimy [[wikipedia:Biofilm|biofilm]] created by bacteria that coated the voids once occupied by blood vessels and cells. The researchers found that what previously had been identified as remnants of blood cells, because of the presence of iron, were actually framboids; microscopic mineral spheres bearing iron. They found similar spheres in a variety of other fossils from various periods, including an [[wikipedia:ammonite|ammonite]]. In the ammonite they found the spheres in a place where the iron they contain could not have had any relationship to the presence of blood.
 
   
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Most recent research on ''Tyrannosaurus'' locomotion does not narrow down speeds further than a range from 17 to 40 kilometres per hour (11 to 25 mph), i.e. from walking or slow running to moderate-speed running. For example, a 2002 paper in the journal ''[[wikipedia:Nature (journal)|Nature]]'' used a mathematical model (validated by applying it to three living animals, [alligators, chickens, and humans; additionally later eight more species including emus and ostriches<ref>Hutchinson, J.R., ''Biomechanical Modeling and Sensitivity Analysis of Bipedal Running Ability. II. Extinct Taxa'', from the Journal of Morphology, vol. 262, issue 1, pp. 441–461. (2004). [http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf]</ref>) to gauge the leg muscle mass needed for fast running (over 40 kilometres per hour (25 mph)).<ref name="HutchinsonGarcia2002TrexSlow"/> They found that proposed top speeds in excess of 40 kilometres per hour (25 mph) were unfeasible, because they would require very large leg muscles (more than approximately 40&ndash;86%&nbsp;of total body mass.) Even moderately fast speeds would have required large leg muscles. This discussion is difficult to resolve, as it is unknown how large the leg muscles actually were in ''Tyrannosaurus''. If they were smaller, only 18 kilometres per hour (11 mph) walking/jogging might have been possible.<ref name="HutchinsonGarcia2002TrexSlow"/>
===Skin and feathers===
 
[[File:Dilong dinosaur.jpeg|thumb|left|Dilong]]
 
In 2004, the scientific journal ''[http://en.wikipedia.org/wiki/Nature_%28journal%29 Nature]'' published a report describing an early tyrannosauroid, ''[[Dilong|Dilong paradoxus]]'', from the famous [http://en.wikipedia.org/wiki/Yixian_Formation Yixian Formation] of China. As with many other theropods discovered in the
 
Yixian, the fossil skeleton was preserved with a coat of filamentous structures which are commonly recognized as the precursors of [http://en.wikipedia.org/wiki/Feather feathers]. It has also been proposed that ''Tyrannosaurus'' and other closely related tyrannosaurids had such protofeathers. However, skin impressions from large tyrannosaurid specimens show mosaic scales. While it is possible that protofeathers existed on parts of the body which have not been preserved, a lack of [http://en.wikipedia.org/wiki/Thermal_insulation insulatory] body covering is consistent with modern multi-ton mammals such as [http://en.wikipedia.org/wiki/Elephants elephants], [http://en.wikipedia.org/wiki/Hippopotamus hippopotamus], and most species of [http://en.wikipedia.org/wiki/Rhinoceros rhinoceros]. And in 2012, another feathered tyrannosaurid, ''[[Yutyrannus]] huali'', was discovered.
 
   
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A study in 2007 used computer models to estimate running speeds, based on data taken directly from fossils, and claimed that ''T. rex'' had a top running speed of 8 metres per second (18 mph). An average professional football (soccer) player would be slightly slower, while a human sprinter can reach 12 metres per second (27 mph). Note that these computer models predict a top speed of 17.8 metres per second (40 mph) for a 3 kilograms (6.6 lb) ''[[wikipedia:Compsognathus|Compsognathus]]''<ref name="SellersManning2007ProcRSocB"</ref>''Estimating dinosaur maximum running speeds using evolutionary robotics'', from the Journal of Proc. R. Soc. B. Published by The Royal Society, (July 2007). [http://dinonews.net/rubriq/articles.php5?action=open&ref=2007_sellers_speed]. Written by Sellers, W.I., and Manning, P.L. (vol. 274, pp. 2711.</ref><ref>[http://news.bbc.co.uk/2/hi/science/nature/6956867.stm ''T. rex 'would outrun footballer''',] by Seward, L. (2007-08-21). Publishing by BBCNews.</ref> (probably a juvenile individual).<ref name=compysize>Callison, G., and H. M. Quimby (1984) ''Tiny dinosaurs: Are they fully grown?'', from the Journal of Vertebrate Paleontology, vol. 3 , pp. 200–209.</ref>
[[File:800px-Young Tyrannosaurus rex 02.jpg|thumb|Restoration of a young Tyrannosaurus, depicted with filamentous feathers.]]
 
   
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Those who argue that ''Tyrannosaurus'' was incapable of running estimate the top speed of ''Tyrannosaurus'' at about 17 kilometres per hour (11 mph). This is still faster than its most likely prey species, [[hadrosaurid]]s and [[wikipedia:Ceratopsia|ceratopsians.]]<ref name="HutchinsonGarcia2002TrexSlow"/> In addition, some advocates of the idea that ''Tyrannosaurus'' was a predator claim that tyrannosaur running speed is not important, since it may have been slow but still faster than its probable prey.<ref name ="manning2008">Manning P, Carpenter, Kenneth; & Larson, Peter E. ''Tyrannosaurus rex, the Tyrant King (Life of the Past)'', chapter 12, T. rex speed trap. Publisher: Indiana University Press, in Bloomington ,(2008), Pages 205-228. ISBN 0-253-35087-5</ref> However, Paul and Christiansen (2000) argued that at least the later ceratopsians had upright forelimbs and the larger species may have been as fast as rhinos.<ref name="PaulChristiansen2000NeoceratopsianForelimbPosture">''Forelimb posture in neoceratopsian dinosaurs: implications for gait and locomotion'', from the Journal of Paleobiology, vol. 26, issue 3, page 450, (September, 2000). [http://www.bioone.org/perlserv/?request=get-document&doi=10.1666%2F0094-8373(2000)026%3C0450%3AFPINDI%3E2.0.CO%3B2]. By Paul, G.S., and Christiansen, P.</ref> Healed ''Tyrannosaurus'' bite wounds on ceratopsian fossils are interpreted as evidence of attacks on living ceratopsians (see below). If the ceratopsians that lived alongside ''Tyrannosaurus'' were fast, that casts doubt on the argument that ''Tyrannosaurus'' did not have to be fast to catch its prey.<ref name="Hanna2002MultipleInjuriesBigAl"/>
As an object increases in size, its ability to retain heat increases due to its decreasing [http://en.wikipedia.org/wiki/Surface_area surface area]-to-[http://en.wikipedia.org/wiki/Volume volume] ratio. Therefore, as large animals [http://en.wikipedia.org/wiki/Evolution evolve] in or [http://en.wikipedia.org/wiki/Biological_dispersal disperse] into warm climates, a coat of fur or feathers loses its [http://en.wikipedia.org/wiki/Natural_selection selective] advantage for thermal insulation and can instead become a disadvantage, as the insulation traps excess heat inside the body, possibly overheating the animal. Protofeathers may also have been secondarily lost during the evolution of large tyrannosaurids like ''Tyrannosaurus'', especially in warm Cretaceous climates. If anything, the feathers would've been used to show off during courtship to attract mates in large tyrannosaurs. Even though the larger adult tyrannosaurs probably didn't have any feathers, the babies, which were much smaller and needed more warmth than the adults, probably hatched with a full coat of downy feathers and lost them as they grew. [[File:Tyr.png|thumb|left|A Feathered Tyrannosaurus]]
 
   
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==History==
== Killer Instinct ==
 
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[[Image:Tyrannosaurus skeleton.jpg|thumb|Skeletal restoration by William D. Matthew from 1905, which was the first reconstruction of ''Tyrannosaurus rex'' ever published<ref name="LindaHall">''The First ''Tyrannosaurus'' Skeleton, 1905'', published by Linda Hall, of the Library of Science, Engineering and Technology. [http://www.lindahall.org/events_exhib/exhibit/exhibits/dino/osb1905.htm].</ref>]]
There has been ongoing debate as to how ''Tyrannosaurus'' found its food. Most people believe it was a predator, hunting down and killing its food in the same way modern lions do. However, others believe it was a scavenger, as evidenced by its large olfactory bulbs (which indicate a phenomenal sense of smell). The best [[File:Imgret-rex.jpg|thumb|left]]possible conclusion is that ''T. rex ''was both a part time hunter and scavenger, since no carnivore relies on just one of those things alone. Evidence has shown that T. rex was also cannibalistic (It may shock us, but Lions do this quite often) when the situation demanded it, or after killing its own kind for mating or territory. There's also evidence that ''Tyrannosaurus rex ''hunted in groups, from when Phil Currie found a large number of ''<nowiki>Tyrannosaurus'</nowiki>'' close, more primitive relative ''Albertosaurus ''in Canada that were all of different ages, and since ''Albertosaurus'', which was more primitive and not as smart as its more famous cousin, hunted in groups, then why shouldn't ''T. rex'' have done the same?[[File:Tyrannosaurus 3D Model.jpg|thumb|234px|Tyrannosaurus 3D Model]]
 
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[[wikipedia:Henry Fairfield Osborn|Henry Fairfield Osborn]], president of the [[wikipedia:American Museum of Natural History|American Museum of Natural History]], named ''Tyrannosaurus rex'' in 1905. The generic name is derived from the Greek words ''τυραννος'' (''tyrannos'', meaning "tyrant") and ''σαυρος'' (''sauros'', meaning "lizard"). Osborn used the Latin word ''rex'', meaning "king", for the specific name. The full [[wikipedia:Binomial nomenclature|binomial]] therefore translates to "tyrant lizard king," emphasizing the animal's size and perceived dominance over other species of the time.<ref name="osborn1905"/>
   
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=== Earliest finds ===
The concept that makes ''Tyrannosaurus rex'' so deadly is that it had a huge 5 foot (1.5 metre) long skull that weighed well over 500&nbsp;lbs (225&nbsp;kg) in weight and great jaws that could dislocate like a snake to swallow large pieces of meat. It also had banana-sized teeth (12 in. or 30&nbsp;cm), some of the largest in the animal kingdom, and could bite 500-600&nbsp;lbs. (227–273&nbsp;kg.) of meat off at a time and swallow it whole, sometimes breaking the teeth off when biting but growing them back repeatedly. Unlike most predators, ''T. rex'' would also eat basically the whole carcass, bones and all. We know because we've found ''Tyrannosaurus'' coprolites (fossilized dung) with ceratopsian and hadrosaur bones in it. The teeth made ''Tyrannosaurus'' different from most predators, because these teeth were blunter, stronger, and more suited to crush bone and penetrate armor instead of slice through flesh. Another discovery seems to show that ''T. rex'' also had a very infectious bite from the teeth, since the serrations in the them were much larger than other theropoods, and probably held pieces of rotten meat in them, which allowed harmful bacteria to grow and cause disease when the ''Rex'' bit down on prey items, so even if the'' T. rex'' didn't get the kill on the first bite, the prey would eventually die of infection and the ''T. rex ''would just track it down using its keen sense of smell and eat it after it'd died or became too weak to fight. It
 
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Teeth from what is now documented as a ''T. rex'' were found in 1874 by A. Lakes near [[wikipedia:Golden, Colorado|Golden, Colorado]]. In the early 1890s, J. B. Hatcher collected postcranial elements in eastern Wyoming. The fossils were believed to be from a large species of ''Ornithomimus'' (''O. grandis'') but are now considered ''T. rex''. Vertebral fragments found by E. D. Cope in western South Dakota in 1892 and named as ''Manospondylus gigas'' have also been reclassified as ''T. rex''.<ref name=quinlanetal2007>Brent H. Breithaupt, Elizabeth H. Southwell and Neffra A. Matthews, (2005-10-18). "In Celebration of 100 years of ''Tyrannosaurus Rex'': ''Manospondylus Gigas'', ''Ornithomimus Grandis'', and ''Dynamosaurus Imperiosus'', the Earliest Discoveries of Tyrannosaurus Rex in the West", from the conference of the 2005 Salt Lake City Annual Meeting, [http://gsa.confex.com/gsa/2005AM/finalprogram/index.html]. Book: ''Abstracts with Programs'', vol. 37, issue 7, published by: the Geological Society of America, pp. 406. [http://gsa.confex.com/gsa/2005AM/finalprogram/abstract_96150.htm].</ref>
   
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[[Image:T.rex mount.png|left|thumb|Scale model of the never-completed ''Tyrannosaurus rex'' exhibit planned for the [[wikipedia:American Museum of Natural History|American Museum of Natural History,]] by [[wikipedia:Henry Fairfield Osborn|H.F. Osborn]].|link=Special:FilePath/T.rex_mount.png]]
[[File:Cnkumj7ddp7lvnxhvvqq.jpg|thumb|left|292px|A steel Tyrannosaurus head]]
 
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[[wikipedia:Barnum Brown|Barnum Brown]], assistant curator of the American Museum of Natural History, found the first partial skeleton of ''T. rex'' in eastern Wyoming in 1900. H. F. Osborn originally named this skeleton ''Dynamosaurus imperiosus'' in a paper in 1905. Brown found another partial skeleton in the Hell Creek Formation in Montana in 1902. Osborn used this [[wikipedia:Holotype|holotype]] to describe ''Tyrannosaurus rex'' in the same paper in which ''D. imperiosus'' was described.<ref>Osborn, H.F. (1905), "''Tyrannosaurus'' and other Cretaceous carnivorous dinosaurs", from the Journal of the Bulletin of the American Museum of Natural History, vol. 21, pp. 259–265.</ref> Had it not been for page order, ''Dynamosaurus'' would have become the official name. The original ''Dynamosaurus'' material resides in the collections of the [[wikipedia:Natural Histpry Museum|Natural History Museum]], in London.<ref name="Breithaup">Breithaup, BH, & Southwell EH, Matthews NA, (2006), "''Dynamosaurus Imperiosus'' and the earliest discoveries of ''Tyrannosaurus Rex'' in Wyoming and the West", from the Journal of the New Mexico Museum of Natural History and Science Bulletin, vol. 35, pp. 257-258. [http://www.nmnaturalhistory.org/science/bulletins/35/sci_bulletin35_32.pdf].</ref>
   
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In total, Brown found five ''Tyrannosaurus'' partial skeletons. In 1941, Brown's 1902 find was sold to the [[wikipedia:Carnegie Museum of Natural History|Carnegie Museum of Natural History]] in Pittsburgh, Pennsylvania. Brown's fourth and largest find, also from Hell Creek, is on display in the [[wikipedia:American Museum of Natural History|American Museum of Natural History]], in New York.<ref name="hornerlessem1993">John R. Horner & [[wikipedia:Don Lessem|Don Lessem,]] ''The complete T. rex'', published by: Simon & Schuster, in New York City, (1993), ISBN 0-671-74185-3</ref>
also seems as though ''T. rexes'' in the North fought against ''[[Triceratops]]'', ''[[Ankylosaurus]]'', ''[[Edmontosaurus]]'', and ''[[Pachycephalosaurus]]'', while ones in the South fought against all of those plus a large sauropod called ''[[Alamosaurus]]''.
 
   
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Although there are numerous skeletons in the world, only one track has been documented — at Philmont Scout Ranch in northeast New Mexico. It was discovered in 1983 and identified and documented in 1994.<ref>[http://esp.cr.usgs.gov/info/kt/footprint.html Footprint of a Giant.] From the Online guide to the continental Cretaceous-Tertiary boundary in the Raton basin, Colorado and New Mexico. (United States Geological Survey.)</ref>
The average bite force of ''Tyrannosaurus rex'' astounded scientists when they used calculations from crocodile bite forces to find out that ''Tyrannosaurus rex'' had a bite force of 60,000 newtons (6.8 tons) of pressure and perhaps even more. Higher estimates were made by professor Mason B. Meers of the University of Tampa in 2003. In his study, Meers estimated a possible bite force of around 183000 to 235000 newtons or 18.3 to 23.5 metric tons; a bite force equivalent to that of the largest Megalodon shark specimens. Other studies say the neck could lift 5 tons. This tremendous amount of force is enough to easily crush bone and bite through a steel oil drum, and also is by far the most powerful bite force of any terrestrial animal that ever lived, surpassing any modern-day animal, such as sharks, crocodiles, or hippos. Tyrannosaurs could probably use hunting tactics which required lunging at prey from short distances, and then crushing them with its jaws. It also could break bones with it's tail, teeth, and could also do so by ramming into prey with its rock-hard head. ''T. rex'' was also the most muscularly built theropod ever, even its tiny arms were strong, being able to lift 500&nbsp;lbs. (227&nbsp;kg.) with each arm, crushing any Olympic record for weight-lifting. The exact use for its arms are unknown, but most scientists agree it was to grab onto struggling prey with those 2-inch (5-cm.) long, hook-like claws while its huge jaws finished it off with a bite to the neck. They also could've been used to grab on at first while mating or to help lift itself up off the ground. Most scientists agree that ''T. rex's'' arms got so small throughout evolution from its jaws becoming so big and powerful, so the arms were less needed, and if ''T. rex'' hadn't gone extinct, the arms might've completely disappeared all together.
 
   
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=== Notable specimens ===
[[File:Kd pop big1.jpg|thumb|238px|A steel Tyrannosaurus head breaking the roof of a car]]
 
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[[Image:Sue, at the FMoNH.jpg|thumb|"Sue" the ''Tyrannosaurus'', [[wikipedia:Field Musuem of Natural History|Field Museum of Natural History]], Chicago, showing the forelimbs. The '[[wikipedia:Furcula|wishbone]]' is between the forelimbs.]]
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[[wikipedia:Sue Hendrickson|Sue Hendrickson]], amateur paleontologist, discovered the most complete (more than 90%) and, until 2001, the largest, ''Tyrannosaurus'' fossil skeleton known in the Hell Creek Formation near Faith, South Dakota, on 12 August 1990. This ''Tyrannosaurus'', nicknamed "Sue" in her honor, was the object of a legal battle over its ownership. In 1997 this was settled in favor of Maurice Williams, the original land owner, and the fossil collection was sold at auction for USD 7.6 million, making it the most expensive dinosaur skeleton to date. It has now been reassembled and is currently exhibited at the [[wikipedia:Field Museum of Natural History|Field Museum of Natural History]]. A study of this specimen's fossilized bones showed that "Sue" reached full size at age 19 and died at age 28, the longest any tyrannosaur is known to have lived.<ref name="Stokstad2004TRExGrowthSpurt">Stokstad, E.,"Bone Study Shows ''T. rex'' Bulked Up With Massive Growth Spurt", from the ''Science'' journal, (13 August 2004), vol. 305, issue 5686, pp. 930–931. [http://www.sciencemag.org/cgi/content/summary/305/5686/930a].</ref> The "Sue" specimen apparently died from a massive bite to the head, which could only have been inflicted by another tyrannosaur.<ref name="Brochu2003">''Lessons From A Tyrannosaur: The Ambassadorial Role Of Paleontology'', by Brochui, C.A., from the ''Palaios'' journal. Vol. 18, issue 6, (December, 2003). [http://www.bioone.org/perlserv/?request=get-document&doi=10.1669%2F0883-1351(2003)018%3C0475%3ALFATTA%3E2.0.CO%3B2]. Page: 475.</ref>
   
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Another ''Tyrannosaurus'', nicknamed "Stan", in honor of amateur paleontologist Stan Sacrison, was found in the Hell Creek Formation near Buffalo, South Dakota, in the spring of 1987. After 30,000 hours of digging and preparing, a 65% complete skeleton emerged. Stan is currently on display in the Black Hills Museum of Natural History Exhibit in Hill City, South Dakota, after an extensive world tour. This tyrannosaur, too, was found to have many bone pathologies, including broken and healed ribs, a broken (and healed) neck and a spectacular hole in the back of its head, about the size of a ''Tyrannosaurus'' tooth. Both Stan and Sue were examined by Peter Larson.
   
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In the summer of 2000, Jack Horner discovered five ''Tyrannosaurus'' skeletons near the Fort Peck Reservoir in Montana. One of the specimens, dubbed "C. rex," was reported to be perhaps the largest ''Tyrannosaurus'' ever found.<ref name="bbc-horner">"''Dig pulls up five T. rex specimens''", from BBC News (10th, October, 2000). [http://news.bbc.co.uk/2/hi/science/nature/965609.stm].</ref>
Although it was the top predator, ''Tyrannosaurus rex'' had a very tough life, most not even living past their early 30's (even Sue died at 29), but ''T. rex'' has proven to also be a very resilient dinosaur. Nearly every adult ''Tyrannosaurus'' specimen found has wounds that it have been healed, but would've killed nearly any other animal.For instance, in one specimen named Sue, it had suffered and survived injuries such as broken ribs, infections in the vertebrae and legs, and also had arthritis. Other specimens have also been healed from ''Triceratops'' horns, ''Ankylosaurus'' clubs, and even bitemarks from other tyrannosaurs. In fact one specimen nicknamed Stan even had a piece of the back of his skull and brain case bitten out of and he still lived for several more years. Aside from fighting some of the toughest herbivores that nature's ever produced, like ''Triceratops'' and ''Ankylosaurus'', they also fought amongst themselves frequently. Nearly every complete or mostly complete skull found has bite marks from the only large theropod around, another ''T. rex''. They most likely fought over mates, territory, or food. ''Tyrannosaurus'' and its cousins were so successful that whenever a tyrannosaur moved into a territory, it drove out any other large predator, and were soon the only large predators in the area.[[File:Xtreemdinos8.jpg|thumb|left|Tyrannosaurus eating]]''T. rex's'' speed has been a topic of discussion for a while. The scientists that believe ''T. rex'' was a scavenger say that it was a slow-moving, lumbering animal that could barely run 15&nbsp;mph. However, some speculate, that since ''T. rex'' had some of the longest and most muscular legs of any bipedal dinosaur, it was a fast runner. In fact its legs and pelvis alone made up half of the tyrant lizard's body weight, and the tail alone weighed a full ton, designed to hold extra muscle mass and counter-balance its enormous head. Another study on the famous ''Tyrannosaurus ''specimen nicknamed Sue also shows how deep indentations on the leg bones where muscle once was, suggesting high concentration of the tissue. Also, unlike most other large theropods, ''T. rex'' had a longer shin bone than a femur bone, giving it an ostirich-like build and shows that ''T. rex'' possibly was fairly fast. Scientists that believe ''T. rex'' was a predator say that it could run 25-28&nbsp;mph (40–45&nbsp;km/h), faster than Olympic sprinters! Ao far it was confirmed that T.rex was a slow reptile, running up to 11&nbsp;mph (18 kph). Even though ''T. rex'' wasn't that fast, it was still capable of taking down large prey. It also seems as though if ''T. rex'' was a predator, than it held its prey down with one of its feet, using the other one and its long tail for balance, and then taking a bite out if its prey's neck, severing the spine. ''T. rex'' also likely had specialized pads on the soles of its feet like elephants today to feel low frequencies in the ground to find and locate its prey like ceratopsians or ankylosaurs.
 
   
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[[Image:Tyrannosaurus Jane.jpg|thumb|right|"Jane" at the Burpee Museum in Rockford, Illinois.|link=Special:FilePath/Tyrannosaurus_Jane.jpg]]
Another terrifying aspect about ''Tyrannosaurus rex'' was the size of its brain. It was the smartest of the large theropods, and its brain was about the size of a gorilla's or a coconut. Recent studies show that ''T. rex'' was probably about as smart as a lion, meaning this dinosaur could use strategic thinking to take down tough prey like ''Triceratops'' and ''Ankylosaurus''. ''T. rex ''probably became so smart because unlike other large theropods, which hunted large, small-brained sauropods, it hunted tough animals that were about the same size, like ''Triceratops'', so it would need to come up with a plan to kill it. That can also explain why the teeth were so much broader, thicker, and stronger than other carnivores, since there was more armor that needed to be bitten through. This brain size may also have led ''T. rex ''to be able to form a family pack, letting the juveniles chase after the prey items into the jaws of the adults, like lions do today. Hunting in packs or pairs could also be a factor in being able to take down tough prey. If ''T. rex'' hunted in a pack, most likely the juveniles would chase the prey towards the more powerful adults, where they would kill it. If it hunted in pairs, they probably attacked together on each side. If it was alone, then the tyrannosaur probably waited until it was ready to attack, and then would charge and repeatedly bite down until thge prey became weak and died. The large brain also helped ''T. rex'' take better care of its young, so the next generation of killers had a greater chance of surviving. The skull of ''T. rex'' also shows that it had large eyes that faced forward, giving it three-dimensional binocular vision, while most theropods had eyes that were on the sides of their heads. Considering how large its eyes were and how good of a sense of smell it had, there's also been debate as to whether ''Tyrannosuarus'' was a part-time nocturnal hunter.
 
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In 2001, a 50% complete skeleton of a juvenile ''Tyrannosaurus'' was discovered in the Hell Creek Formation in Montana, by a crew from the [[wikipedia:Burpee Museum of Natural History|Burpee Museum of Natural History]] of Rockford, Illinois. Dubbed "[[wikipedia:Jane (dinosaur)|Jane the Rockford T-Rex]]," the find was initially considered the first known skeleton of the pygmy tyrannosaurid ''[[wikipedia:Nanotyrannus|Nanotyrannus]]'' but subsequent research has revealed that it is more likely a juvenile ''Tyrannosaurus''.<ref>Currie, PJ Huru, JH, & Sabath, K, (2003). "''Skull structure and evolution in tyrannosaurid dinosaurs''" from the Journal of ''Acta Palaeontologica Polonica'', vol. 48, issue 2, pp. 227-234 [http://www.biology.ualberta.ca/faculty/philip_currie/uploads/pdfs/2003/2003TyrannosauridEvolution.pdf].</ref> It is the most complete and best preserved juvenile example known to date. Jane has been examined by [[wikipedia:Jack Horner (paleontologist)|Jack Horner]], [[wikipedia:Pete Larson|Pete Larson]], [[wikipedia:Robert Bakker|Robert Bakker]], [[wikipedia:Greg Erickson|Greg Erickson]] and several other renowned paleontologists, because of the uniqueness of her age. Jane is currently on exhibit at the Burpee Museum of Natural History in Rockford, Illinois.<ref>Henderson, M, ''The origin, systematics, and paleobiology of Tyrannosauridae'', edited by: Henderson, M, & published by: the Northern Illinois University Press, in Dekalb, Illinois, (In press). Chapter: Nano No More: The death of the pygmy tyrant</ref><ref name="visitjane">[http://www.visitjane.com/index.cfm Visit Jane the Dinosaur at the Burpee Museum, Rockford, Illinois.]</ref>
== Taxonomy == [[File:Tyrannosaurus Sue.JPG|thumb|Sue]]For a long time ''T. rex'' was considered part of the carnosaur genus, like ''[[Allosaurus]]'', but a closer analysis a few years ago showed that it was actually part of its own genus; the tyrannosaurids, which descended from coelurosaurs like ''[[Velociraptor]]''. While'' Tyrannosaurus ''was by far the biggest tyrannosaurid, it wasn't the only one. It had numerous relatives; ''[[Daspletosaurus]]'', ''[[Albertosaurus]]'', and ''[[Tarbosaurus]]'' are all part of the tyrannosaur family.
 
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The earliest known tyrannosaurs were actually small hunters from the [[Jurassic]] Period, like ''[[Guanlong]]''. Of all it's relatives, ''[[Daspletosaurus]]'' is believed to be the direct ancestor of ''T. rex, ''due to its very similar appearance. The skull of a small tyrannosaur, ''[[Nanotyrannus]]'', found in South Dakota, was later thought to be from an adolescent ''T. rex ''but it is still possibly a separate species or genus. ''T. rex'' had a relatively short neck for such a large theropod, but was very well muscled and designed to withstand much more force from its powerul bite than other theropods were. Although ''Tyrannosaurus rex'' was the peak of tyrannosaur and carnivourous dinosaur evolution, it was an evolutionary dead end, with its closest descendants being birds, because of the K-T Extinction caused by a massive asteroid or comet. [[File:Tyranroar.jpg|thumb|left]]
 
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In a press release on 7 April 2006, Montana State University revealed that it possessed the largest ''Tyrannosaurus'' skull yet discovered. Discovered in the 1960s and only recently reconstructed, the skull measures 59 inches (150 cm) long compared to the 55.4 inches (141 cm) of “Sue’s” skull, a difference of 6.5%.<ref>Museum unveils world's largest ''T-rex'' skull. [http://www.montana.edu/cpa/news/nwview.php?article=3607].</ref><ref>New Biggest ''T-rex'' Skull. [http://palaeoblog.blogspot.com/2006/04/new-biggest-t-rex-skull.html]. By Ryan, M.J.</ref>
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==Cultural Influence==
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Since it was first described in 1905, ''Tyrannosaurus rex'' has become the most widely recognized dinosaur in [[wikipedia:Popular culture|popular culture]]. It is the only dinosaur which is routinely referred to by its full scientific name (''Tyrannosaurus rex'') among the general public, and the scientific abbreviation ''T. rex'' has also come into wide usage (commonly misspelled "T-Rex").<ref name="brochu2003"/> [[wikipedia:Robert T. Bakker|Robert T. Bakker]] notes this in ''[[wikipedia:The Dinosaur Heresies|The Dinosaur Heresies]]'' and explains that a name like "''Tyrannosaurus rex'' is just irresistible to the tongue."<ref name="bakker1986"/>
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Museum exhibits featuring ''T. rex'' are very popular; an estimated 10,000 visitors flocked to Chicago's Field Museum on the opening day of its "Sue" exhibit in 2003.<ref name="suerecord">''Guinness World Records 2003'', Folkard, C. Publisher: Guinness World Records Ltd., 2002. page 90. ISBN 1892051176</ref> ''T. rex'' has appeared numerous times on television and in films, notably (in chronological order) ''[[wikipedia:The Lost World (1925 film)|The Lost World]]'', ''[[wikipedia:King Kong (1933 film)|King Kong]]'', ''[[The Land Before Time]]'', the ''[[wikipedia:Jurassic Park (franchise)|Jurassic Park]]'' films, ''[[wikipedia:Barney and Friends|Barney and Friends]]'', ''[[wikipedia:Toy Story|Toy Story]]'', ''[[wikipedia:Toy Story 2|Toy Story 2]]'', ''[[wikipedia:Walking with Dinosaurs|Walking with Dinosaurs]]'', and ''[[wikipedia:Night at the Museum|Night at the Museum]]'', among many others. A number of books and comic strips, including ''[[wikipedia:Calvin and Hobbes|Calvin and Hobbes]]'' and [[wikipedia:Dinosaur Comics|Dinosaur Comics]], have also featured ''Tyrannosaurus'', which is typically portrayed as the biggest and most terrifying carnivore of all. At least one musical group, the band [[wikipedia:T.Rex (band)|T.Rex]], is named after the species. ''Tyrannosaurus''-related toys, including numerous video games and other merchandise, remain popular. Various businesses have capitalized on the popularity of ''Tyrannosaurus rex'' by using it in advertisements.
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===General Impact===
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''Tyrannosaurus rex'' is unique among dinosaurs in its place in modern culture; paleontologist Robert Bakker has called it "the most popular dinosaur among people of all ages, all cultures, and all nationalities".<ref name="Bakker">Bakker, Robert. Edited by Fiffer, S. ''Tyrannosaurus Sue'' (2000). Publisher: W. H. Freeman & Company, in New York ISBN 0-7167-4017-6 pp. xi-xiv Chapter: Prologue.</ref> From the beginning, it was embraced by the public. Henry Fairfield Osborn billed it the greatest hunter to have ever walked the earth. He stated in 1905,<ref name ="Horner93">John "Jack" Horner and Don "Dino" Lessem, ''The Complete T. Rex'' (New York: Simon & Schuster, 1993), pages 58-62</ref>
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<center>''I propose to make this animal the type of the new genus, ''Tyrannosaurus'', in reference to its size, which far exceeds that of any carnivorous land animal hitherto described...This animals is in fact the ne plus ultra of the evolution of the large carnivorous dinosaurs: in brief it is entitled to the royal and high sounding group name which I have applied to it.''</center>
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''Tyrannosaurus'' gained widespread public attention on December 30, 1905, when the ''New York Times'' hailed ''T. rex'' as "the most formidable fighting animal of which there is any record whatever," the "king of all kings in the domain of animal life," "the absolute warlord of the earth," and a "royal man-eater of the jungle." <ref>“Mining for Mammoths in the Badlands: How Tyrannosaurus Rex Was Dug Out of His 8,000,000 Year old Tomb,” ''The New York Times'', December 3rd, 1905, page SM1.</ref> In 1906, ''Tyrannosaurus'' was dubbed the "prize fighter of antiquity" and the "Last of the Great Reptiles and the King of Them All."<ref>"The Prize Fighter of Antiquity Discovered and Restored," ''The New York Times'' December 30th, 1906, page 21.</ref>
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In 1942, Charles R. Knight painted a mural incorporating ''Tyrannosaurus'' facing a ''[[Triceratops]]'' in the Field Museum of Natural History for the [[wikipedia:National Geographic Society|National Geographic Society]], establishing the two dinosaurs as enemies in popular thought;<ref name="Bakker1986"/> paleontologist Phil Currie cites this mural as one of his inspirations to study dinosaurs.<ref name="Horner93"/> Bakker said of the imagined rivalry between ''Tyrannosaurus'' and ''Triceratops'', "No matchup between predator and prey has ever been more dramatic. It’s somehow fitting that those two massive antagonists lived out their co-evolutionary belligerence through the very last days of the very last epoch of the Age of Dinosaurs."<ref name="Bakker1986">Bakker, R.T. 1986. ''The Dinosaur Heresies''. New York: Kensington Publishing, p. 240. On that page, Bakker has his own ''T. rex''/''Triceratops'' fight.</ref>
   
Of the 31 specimens found, the most famous, most complete, and largest ''T. rex ''skeleton on display is Sue, a 42 foot (13 m) long ''Tyrannosaurus'' found in the badlands of South Dakota in 1990 by Susan Hendrickson. Sue's the most complete skeleton of any tyrannosaur, and was auctioned off in Washington D.C. for over $8,000,000. The skeleton is now on display in the Field Museum in Chicago, Illinois for everyone to see, but its skull is on a seperate case because it was too heavy to put on the actual skeleton, so they made a lighter replica and put it on the frame instead. Sue was named after the paleontologist who found it, but scientists aren't quite sure what its gender is. Not only is Sue the most complete and largest displayed ''T. rex'', but it's also the oldest, dying at the age of 28. This seems to suggest tyrannosaurs grew continuously as they aged. Sue has given the most information of any ''T. rex'' skeleton yet, and is one of only a few ''Tyrannosaurus'' with a complete skull and forelimb. Despite being so large and ferocious, Sue's bones have shown just how tough its life was. It has healed rib fractures, healed infected broken leg bones, bites taken out of its vertebrae by other tyrannosaurs, and even arthritis. Another significant specimen found by Dr. Jack Horner, curator of the Museum of the Rockies in Bozeman, Montana, shows medullary tissue in the bone sctructure, tissue only found in modern-day pregnant birds. This is a very significant find because it's the first dinosaur ever discovered to show that dinosaurs (or at least coelurosaurs) had a birth cycle much closer to birds than previously thought, and also shows the first proven male or female ''Tyrannosaurus''. Some other famous ''T. rex'' specimens are Stan, Thomas, Samson, and Jane.
 
==Popular Culture==
 
*''Tyrannosaurus'' is possibly the most famous of dinosaurs, ever since its discovery in 1902, it's been extremely popular, and it's almost always the first dinosaur that comes to mind when the word "Dinosaur" is mentioned, being one of the only dinosaurs where nearly everyone actually fully knows its name.
 
*It is shown in every single dinosaur movie involving dinosaurs barring Walking with Dinosaurs: The 3D Movie. Its first appearance in the movies was in the 1925 film ''The Lost World, ''where it battles an ''Agathaumas''.
 
*It also played an important role in the 1990 book and 1993 famous movie ''Jurassic Park''.
 
*It also appeared in the sequel to 1997 Jurassic Park ''The Lost World: Jurassic Park. ''In this movie it rampaged through San Diego in an attempt to find its offspring.[[File:Tyrannosaurus rex bites Spinosaurus.jpg.jpg|thumb|Tyrannosaurus VS [[Spinosaurus]] from Jurassic Park ///]]
 
*It later appeared in the 2001 third sequel of Jurassic Park ''Jurassic Park III.'' Here a sub-adult male ''Tyrannosaurus'' ate the remains of a ''Parasaurolophus'' and was killed by a fully grown adult ''Spinosaurus''.
 
**it later appeared in the 2015 fourth sequel of ''Jurassic Park'', ''Jurassic World''. Here the same female Tyrannosaurus from the first film, fights the hybrid dinosaur antagonist, the Indominus rex.
 
* It also starred in an episode of the reknown documentary series ''Walking With Dinosaurs'', and two shows from the same producers called ''Prehistoric Park ''and'' Primeval''.
 
*It also appeared in several episodes of the well known documentary ''Jurassic Fight Club, Animal Armageddon, Dinosaurs Decoded, Truth About Killer Dinosaurs, T. rex: New Science, New Beast, Prehistoric Denver, Dino Gangs, Ultimate Guide: Tyrannosaurus rex, Last Day of the Dinosaurs,'' and ''Clash of the Dinosaurs''.
 
*Another documentary it's been in is ''Dinosaur Revolution, ''where it showed how a family of tyrannosaurs lived until the K-T Extinction.
 
*[[File:Tyrannosaurus new.png|thumb|left|Dinosaur Island Tyrannosaurus]]A ''Tyrannosaurus'' named Heart serves as the main protaganist of the 2010 anime film ''You Are Umasou ''and as antagonists in the books and TV shows of <u>Dinotopia</u>.
 
*It's also featured in many games involvong dinosaurs, including all <u>Jurassic Park Games</u>, all <u>Dino Crisis Games</u>, and also <u>Primal Carnage</u>. It has also been featured in the <u>Fossil Fighters</u> series, appearing on the cover of the seque,<u> Fossil Fighters Champions. </u>''Tyrannosaurus ''appears in <u>Turok</u>, as there is a ''T. rex ''that has grown to intense size, as it is nicknamed "Mama Scarface", for the scar on its right eye.
 
*It was also in the IMAX movie, <u>T. rex: Back to the Cretaceous</u>. A giant robotic ''Tyrannosaurus'' is piloted by the red ranger in both the Mighty <u>Morphin' Power Ranger</u> series and the <u>Dino Thunder</u> series.
 
*''Tyrannosaurus'' is also the antagonist of nearly every episode of <u>The Land Before Time</u>.
 
*It also starred in a Hollywood parody called <u>T. rex: A Dinosaur in Hollywood</u>, where they talk about how ''T. rex'' gained its fame throughout its discovery to modern-day movies, and also was in the Disney movie <u>Fantasia</u> where it fought a ''[[Stegosaurus]]'' while the song "The Rite of Spring" played.
 
*It was also a main source for evolution in many episodes of the History Channel show <u>Evolve</u>.
 
*It also served as the main dinosaur in a documentary called <u>Tyrannosaurus Sex</u>, where they talked [[File:Tyrannasaurus Spitter.gif|thumb|Tyrannosaurus from Walking with Dinosaurs]]about how ''T. rex'' and other dinosaurs may have reproduced.
 
*''Tyrannosaurus'' was also an antagonist in the comedy movie <u>Land of the Lost</u> and the Korean film <u>Speckles: the Tarbosaurus</u>, where it was named "One Eye" and killed the family of the main character "Speckles", a ''Tarbosaurus''.
 
*Jack Horner also talked about ''T. rex'' and why he believes it's mostly a scavenger in <u>Valley of the T. rex</u>.
 
*''Tyrannosaurus'' also made a short cameo in <u>Dinosaur Planet</u>.
 
*A ''T. rex'' named Rex is the main protagonist of <u>We're Back! A Dinosaur's Story</u>
 
*''T. rex'' is one of the main dinosaurs in the Dinosaur themed restaurant T-Rex Cafe located in Disney World and Kansas City. It's mascot is also a ''T. rex'' named Dexter.
 
* [[File:T-Rex 3.png|thumb|left|Jurassic World Tyrannosaurus]]A ''T.rex'' named Grumpy by the characters appeared in the 2009 film ''Land of the Lost''.
 
* ''Tyrannosaurus rex'' is seen as The Disneyland train travels to the Primeval World diorama. In it, he is seen reenacting his battle from <u>Fantasia</u>.
 
* In Walt Disney World's Epcot there is a ride known as Ellen's Energy Adventure staring Ellen DeGeneres and Bill Nye the Science Guy, who explore the world of energy, including the use of fossil fuels. During the ride, Bill Nye brings DeGeneres "back in time" to the age of dinosaurs to explain the origin of fossil fuels. During this portion of the ride, several dinosaurs can be seen that are similar to the ones during ''Fantasia's The Rite of Spring''. Most notably, there is a large ''Tyrannosaurus ''attacking a ''Stegosaurus ''over a cliff. This is obviously in reference to ''Fantasia''. At Downtown Disney's [[wikipedia:T-Rex (restaurant)|T-Rex Cafe]], there is a large ''Tyrannosaurus ''with his young.It is even in jurrassic fight club a dinosaur documentry .
 
* Three ''Tyrannosaurus'' (Butch, Nash and Ramsey) appeared in the Disney/Pixar film [[The Good Dinosaur]]
 
==Gallery==
 
*''See [[Tyrannosaurus/Gallery]]''
 
 
==References==
 
==References==
 
<references/>
 
<references/>
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==External links==
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* [http://www.tolweb.org/Tyrannosauridae Tyrannosauridae] "Tree of Life" page, very comprehensive survey by major authority Tom Holtz.
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* [http://www.guardian.co.uk/science/2004/aug/12/dinosaurs.research The secret of ''T. rex'''s colossal size: a teenage growth spurt] ''The Guardian'', 12 August 2004.
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* [http://www.nhm.ac.uk/jdsml/nature-online/dino-directory/detail.dsml?Genus=Tyrannosaurus ''Tyrannosaurus'' in the Dino Directory]
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* [http://www.fieldmuseum.org/sue Sue's homepage]
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* [http://www.bhigr.com/pages/info/info_stan.htm Stan's homepage]
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* [http://www.unearthingtrex.com/ Unearthing ''Tyrannosaurus rex'']
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* [http://www.visitjane.com ''T.rex'' juvenile Jane]
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* [http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?mode=Info&id=436495&lvl=3&lin=f&keep=1&srchmode=1&unlock NBCI's Taxonomy Browser]
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* [http://www.dinosauria.com/jdp/misc/hellcreek.html Cretaceous Hell Creek Faunal Facies] is an example of one tyrannosaur environment, in the Hell Creek Formation of Montana
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* [http://eis.bris.ac.uk/~glxms/scaling.htm Bristol University study on bite forces of predators]
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* [http://www.unmuseum.org/tyran.htm Museum of Unnatural Mystery – Bite force etc. of ''T. rex'']
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* [http://www.stanford.edu/dept/news/pr/96/960827tyrexbite.html Stanford University on bite force of ''T. rex'']
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* [http://www.cosmosmagazine.com/node/639 How ''Tyrannosaurus'' might have had sex]
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* [http://news.nationalgeographic.com/news/2005/03/0324_050324_trexsofttissue.html Recent Discovery of Soft Tissue]
 
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Revision as of 18:38, 8 October 2021


Tyrannoname
Accurate Rex
'Accurate Tyrannosaurus'

Suborder:

Therapoda

Name Translation:

Tyrant Lizard King

Period:

Late Cretaceous (68-65 mya)

Length:

42-49 feet long(12.8-14.9 meters)

Height:

15-21 feet tall (4.5-6.4 meters)

Weight:

6.6-9 tonnes

Tyrannosaurus (pronounced /tɨˌrænəˈsɔːrəs/ or /taɪˌrænoʊˈsɔːrəs/, meaning 'tyrant lizard') is a genus of theropod dinosaur. The famous species Tyrannosaurus rex ('rex' meaning 'king' in Latin), commonly abbreviated to T. rex, is a fixture in popular culture around the world, and is extensively used in scientific television and movies, such as documentaries and Jurassic Park, and in children's series such as The Land Before Time. Tyrannosaurus lived throughout what is now western North America, with a much wider range than other tyrannosaurids. Fossils of T. rex are found in a variety of rock formations dating to the last three million years of the Cretaceous Period, approximately 68 to 65 million years ago; it was among the last non-avian dinosaurs to exist prior to the Cretaceous–Tertiary extinction event.

Like other tyrannosaurids, Tyrannosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to the large and powerful hindlimbs, Tyrannosaurus forelimbs were small, though unusually powerful for their size, and bore two primary digits, along with a possible third vestigial digit. Although other theropods rivaled or exceeded T. rex in size, it was the largest known tyrannosaurid and one of the largest known land predators, measuring up to 13 metres (43 ft.) in length,[1] up to 4 metres (13 ft.) tall at the hips,[2] and up to 6.8 metric tonnes (7.5 short tons) in weight.[3] By far the largest carnivore in its environment, T. rex may have been an apex predator, preying upon hadrosaurs and ceratopsians, although some experts have suggested it was primarily a scavenger.

More than 30 specimens of T. rex have been identified, some of which are nearly complete skeletons. Soft tissue and proteins have been reported in at least one of these specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including life history and biomechanics. The feeding habits, physiology and potential speed of T. rex are a few subjects of debate. Its taxonomy is also controversial, with some scientists considering Tarbosaurus bataar from Asia to represent a second species of Tyrannosaurus and others maintaining Tarbosaurus as a separate genus. Several other genera of North American tyrannosaurids have also been synonymized with Tyrannosaurus. Tyrannosaurus Chicks

Description

Tyrannosaurusscale

Various specimens of Tyrannosaurus rex with a human for scale.

Theropodscalewithhuman

Size comparison of selected giant theropod dinosaurs, with Tyrannosaurus in purple.

Tyrannosaurus rex was one of the largest land carnivores of all time; the largest complete specimen, FMNH PR2081 ("Sue"), measured 12.8 metres (42 ft) long, and was 4.0 metres (13 ft) tall at the hips.[2] Mass estimates have varied widely over the years, from more than 7.2 metric tons (7.9 short tons),[4] to less than 4.5 metric tons (5.0 short tons),[5][6] with most modern estimates ranging between 5.4 and 6.8 metric tons (6.0 and 7.5 short tons).[7][8][9][3] Although Tyrannosaurus rex was larger than the well known Jurassic theropod Allosaurus, it was slightly smaller than Cretaceous carnivores Spinosaurus and Giganotosaurus.[10][11]

The neck of T. rex formed a natural S-shaped curve like that of other theropods, but was short and muscular to support the massive head. The forelimbs were long thought to bear only two digits, but there is an unpublished report of a third, vestigial digit in one specimen.[12] In contrast the hind limbs were among the longest in proportion to body size of any theropod. The tail was heavy and long, sometimes containing over forty vertebrae, in order to balance the massive head and torso. To compensate for the immense bulk of the animal, many bones throughout the skeleton were hollow, reducing its weight without significant loss of strength.[1]

Tyrannosaurus

The largest known T. rex skulls measure up to 5 feet (1.5 m) in length.[13] Large fenestrae (openings) in the skull reduced weight and provided areas for muscle attachment, as in all carnivorous theropods. But in other respects Tyrannosaurus’ skull was significantly different from those of large non-tyrannosauroid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision.[14][15] The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) which may have made the bones more flexible as well as lighter. These and other skull-strengthening features are part of the tyrannosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-tyrannosaurids.[16][17][18] The tip of the upper jaw was U-shaped (most non-tyrannosauroid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a tyrannosaur could rip out with one bite, although it also increased the stresses on the front teeth.[19][20]

T rex restoration

Life restoration of a Tyrannosaurus rex.

The teeth of T. rex displayed marked heterodonty (differences in shape).[21][1] The premaxillary teeth at the front of the upper jaw were closely packed, D-shaped in cross-section, had reinforcing ridges on the rear surface, were incisiform (their tips were chisel-like blades) and curved backwards. The D-shaped cross-section, reinforcing ridges and backwards curve reduced the risk that the teeth would snap when Tyrannosaurus bit and pulled. The remaining teeth were robust, like "lethal bananas" rather than daggers; more widely spaced and also had reinforcing ridges.[22] Those in the upper jaw were larger than those in all but the rear of the lower jaw. The largest found so far is estimated to have been 30 centimetres (12 in) long including the root when the large reptile was alive, making it the largest tooth of any carnivorous dinosaur.[2]

Paleobiology

Life history

T-rex graph

A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids. Tyrannosaurus rex is drawn in black. Based on Erickson et al. 2004.

The identification of several specimens as juvenile Tyrannosaurus rex has allowed scientists to document ontogenetic changes in the species, estimate the lifespan, and determine how quickly the animals would have grown. The smallest known individual (LACM 28471, the "Jordan theropod") is estimated to have weighed only 29.9 kg (66 lb), while the largest, such as FMNH PR2081 ("Sue") most likely weighed over 5400 kg (6 short tons). Histologic analysis of T. rex bones showed LACM 28471 had aged only 2 years when it died, while "Sue" was 28 years old, an age which may have been close to the maximum for the species.[3]

Histology has also allowed the age of other specimens to be determined. Growth curves can be developed when the ages of different specimens are plotted on a graph along with their mass. A T. rex growth curve is S-shaped, with juveniles remaining under 1800 kg (2 short tons) 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 600 kg (1,300 lb) a year for the next four years. At 18 years of age, the curve plateaus again, indicating that growth slowed dramatically. For example, only 600 kg (1,300 lb) separated the 28-year-old "Sue" from a 22-year-old Canadian specimen (RTMP 81.12.1).[3] Another recent histological study performed by different workers corroborates these results, finding that rapid growth began to slow at around 16 years of age.[23] This sudden change in growth rate may indicate physical maturity, a hypothesis which is supported by the discovery of medullary tissue in the femur of a 16 to 20-year-old T. rex from Montana (MOR 1125, also known as "B-rex"). Medullary tissue is found only in female birds during ovulation, indicating that "B-rex" was of reproductive age.[24] Further study indicates an age of 18 for this specimen.[25] Other tyrannosaurids exhibit extremely similar growth curves, although with lower growth rates corresponding to their lower adult sizes.[26]

Over half of the known T. rex specimens appear to have died within six years of reaching sexual maturity, a pattern which 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. One study suggests that the rarity of juvenile T. rex fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and so were not often fossilized. However, this rarity may also be due to the incompleteness of the fossil record or to the bias of fossil collectors towards larger, more spectacular specimens.[26]

Posture

Outdated Trex Posture

Outdated reconstruction (by Charles R. Knight), showing 'tripod' pose.

Updated Trex posture

Replica at Senckenberg Museum, showing modern view of posture.

Like many bipedal dinosaurs, Tyrannosaurus rex was historically depicted as a 'living tripod', with the body at 45 degrees or less from the vertical and the tail dragging along the ground, similar to a kangaroo. This concept dates from Joseph Leidy's 1865 reconstruction of Hadrosaurus, the first to depict a dinosaur in a bipedal posture.[27] Henry Fairfield Osborn, former president of the American Museum of Natural History (AMNH) in New York City, who believed the creature stood upright, further reinforced the notion after unveiling the first complete T. rex skeleton in 1915. It stood in this upright pose for nearly a century, until it was dismantled in 1992.[28] By 1970, scientists realized this pose was incorrect and could not have been maintained by a living animal, as it would have resulted in the dislocation or weakening of several joints, including the hips and the articulation between the head and the spinal column.[29] The inaccurate AMNH mount inspired similar depictions in many films and paintings (such as Rudolph Zallinger's famous mural The Age Of Reptiles in Yale University's Peabody Museum of Natural History)[30] until the 1990s, when films such as Jurassic Park introduced a more accurate posture to the general public. Modern representations in museums, art, and film show T. rex with its body approximately parallel to the ground and tail extended behind the body to balance the head.[20]

Arms

T rex arm

Closeup of forelimb; specimen at National Museum of Natural History, Washington, DC.

When Tyrannosaurus rex was first discovered, the humerus was the only element of the forelimb known.[31] For the initial mounted skeleton as seen by the public in 1915, Osborn substituted longer, three-fingered forelimbs like those of Allosaurus.[32] However, a year earlier, Lawrence Lambe described the short, two-fingered forelimbs of the closely related Gorgosaurus.[33] This strongly suggested that T. rex had similar forelimbs, but this hypothesis was not confirmed until the first complete T. rex forelimbs were identified in 1989, belonging to MOR 555 (the "Wankel rex").[34] The remains of "Sue" also include complete forelimbs.[1] T. rex arms are very small relative to overall body size, measuring only 1 metre (3.3 ft) long. However, they are not vestigial but instead show large areas for muscle attachment, indicating considerable strength. This was recognized as early as 1906 by Osborn, who speculated that the forelimbs may have been used to grasp a mate during copulation.[35] It has also been suggested that the forelimbs were used to assist the animal in rising from a prone position.[29] Another possibility is that the forelimbs held struggling prey while it was dispatched by the tyrannosaur's enormous jaws. This hypothesis may be supported by biomechanical analysis. T. rex forelimb bones exhibit extremely thick cortical bone, indicating that they were developed to withstand heavy loads. The biceps brachii muscle of a full-grown Tyrannosaurus rex was capable of lifting 199 kilograms (439 lb) by itself; this number would only increase with other muscles (like the brachialis) acting in concert with the biceps. A T. rex forearm also had a reduced range of motion, with the shoulder and elbow joints allowing only 40 and 45 degrees of motion, respectively. In contrast, the same two joints in Deinonychus allow up to 88 and 130 degrees of motion, respectively, while a human arm can rotate 360 degrees at the shoulder and move through 165 degrees at the elbow. The heavy build of the arm bones, extreme strength of the muscles, and limited range of motion may indicate a system designed to hold fast despite the stresses of a struggling prey animal.[36]

Soft tissue

In the March 2005 issue of Science, Mary Higby Schweitzer of North Carolina State University and colleagues announced the recovery of soft tissue from the marrow cavity of a fossilized leg bone, from a 68-million-year-old Tyrannosaurus. The bone had been intentionally, though reluctantly, broken for shipping and then not preserved in the normal manner, specifically because Schweitzer was hoping to test it for soft tissue.[37] Designated as the Museum of the Rockies specimen 1125, or MOR 1125, the dinosaur was previously excavated from the Hell Creek Formation. Flexible, bifurcating blood vessels and fibrous but elastic bone matrix tissue were recognized. In addition, microstructures resembling blood cells were found inside the matrix and vessels. The structures bear resemblance to ostrich blood cells and vessels. Whether an unknown process, distinct from normal fossilization, preserved the material, or the material is original, the researchers do not know, and they are careful not to make any claims about preservation.[38] If it is found to be original material, any surviving proteins may be used as a means of indirectly guessing some of the DNA content of the dinosaurs involved, because each protein is typically created by a specific gene. The absence of previous finds may merely be the result of people assuming preserved tissue was impossible, therefore simply not looking. Since the first, two more tyrannosaurs and a hadrosaur have also been found to have such tissue-like structures.[37] Research on some of the tissues involved has suggested that birds are closer relatives to tyrannosaurs than other modern animals.[39]

In studies reported in the journal Science in April 2007, Asara and colleagues concluded that seven traces of collagen proteins detected in purified T. rex bone most closely match those reported in chickens, followed by frogs and newts. The discovery of proteins from a creature tens of millions of years old, along with similar traces the team found in a mastodon bone at least 160,000 years old, upends the conventional view of fossils and may shift paleontologists' focus from bone hunting to biochemistry. Until these finds, most scientists presumed that fossilization replaced all living tissue with inert minerals. Paleontologist Hans Larsson of McGill University in Montreal, who was not part of the studies, called the finds "a milestone", and suggested that dinosaurs could "enter the field of molecular biology and really slingshot paleontology into the modern world."[40]

Subsequent studies in April 2008 confirmed the close connection of T. rex to modern birds. Postdoctoral biology researcher Chris Organ at Harvard University announced, "With more data, they would probably be able to place T. rex on the evolutionary tree between alligators and chickens and ostriches." Co-author John M. Asara added, "We also show that it groups better with birds than modern reptiles, such as alligators and green anole lizards."[41]

The presumed soft tissue was called into question by Thomas Kaye of the University of Washington and his co-authors in 2008. They contend that what was really inside the tyrannosaur bone was slimy biofilm created by bacteria that coated the voids once occupied by blood vessels and cells.[42] The researchers found that what previously had been identified as remnants of blood cells, because of the presence of iron, were actually framboids; microscopic mineral spheres bearing iron. They found similar spheres in a variety of other fossils from various periods, including an ammonite. In the ammonite they found the spheres in a place where the iron they contain could not have had any relationship to the presence of blood.[43]

Skin and feathers

In 2004, the scientific journal Nature published a report describing an early tyrannosauroid, Dilong paradoxus, from the famous Yixian Formation of China. As with many other theropods discovered in the Yixian, the fossil skeleton was preserved with a coat of filamentous structures which are commonly recognized as the precursors of feathers. It has also been proposed that Tyrannosaurus and other closely related tyrannosaurids had such protofeathers. However, rare skin impressions from adult tyrannosaurids in Canada and Mongolia show pebbly scales typical of other dinosaurs.[44] While it is possible that protofeathers existed on parts of the body which have not been preserved, a lack of insulatory body covering is consistent with modern multi-ton mammals such as elephants, hippopotamus, and most species of rhinoceros. As an object increases in size, its ability to retain heat increases due to its decreasing surface area-to-volume ratio. Therefore, as large animals evolve in or disperse into warm climates, a coat of fur or feathers loses its selective advantage for thermal insulation and can instead become a disadvantage, as the insulation traps excess heat inside the body, possibly overheating the animal. Protofeathers may also have been secondarily lost during the evolution of large tyrannosaurids like Tyrannosaurus, especially in warm Cretaceous climates.[45]

Thermoregulation

Tyrannosaurus, like most dinosaurs, was long thought to have an ectothermic ("cold-blooded") reptilian metabolism. The idea of dinosaur ectothermy was challenged by scientists like Robert T. Bakker and John Ostrom in the early years of the "Dinosaur Renaissance", beginning in the late 1960s.[46][47] Tyrannosaurus rex itself was claimed to have been endothermic ("warm-blooded"), implying a very active lifestyle.[6] Since then, several paleontologists have sought to determine the ability of Tyrannosaurus to 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 vertebrates.[23]

Oxygen isotope ratios in fossilized bone are sometimes used to determine the temperature at which the bone was deposited, as the ratio between certain isotopes correlates with temperature. In one specimen, the isotope ratios in bones from different parts of the body indicated a temperature difference of no more than 4 to 5°C (7 to 9°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 geochemist William Showers to indicate that T. rex maintained a constant internal body temperature (homeothermy) and that it enjoyed a metabolism somewhere between ectothermic reptiles and endothermic mammals.[48] Other scientists have pointed out that the ratio of oxygen isotopes in the fossils today does not necessarily represent the same ratio in the distant past, and may have been altered during or after fossilization (diagenesis).[49] Barrick and Showers have defended their conclusions in subsequent papers, finding similar results in another theropod dinosaur from a different continent and tens of millions of years earlier in time (Giganotosaurus).[50] Ornithischian dinosaurs also showed evidence of homeothermy, while varanid lizards from the same formation did not.[51] 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 turtles.[52][53]

Footprints

New Mexico Trex Footprint

The probable Tyrannosaurus rex footprint from New Mexico.

Two isolated fossilized footprints have been tentatively assigned to Tyrannosaurus rex. The first was discovered at Philmont Scout Ranch, New Mexico, in 1983 by American geologist Charles Pillmore. Originally thought to belong to a hadrosaurid, examination of the footprint revealed a large 'heel' unknown in ornithopod dinosaur tracks, and traces of what may have been a hallux, the dewclaw-like fourth digit of the tyrannosaur foot. The footprint was published as the ichnogenus Tyrannosauripus pillmorei in 1994, by Martin Lockley and Adrian Hunt. Lockley and Hunt suggested that it was very likely the track was made by a Tyrannosaurus rex, which would make it the first known footprint from this species. The track was made in what was once a vegetated wetland mud flat. It measures 83 centimetres (33 in) long by 71 centimetres (28 in) wide.[54]

A second footprint that may have been made by a Tyrannosaurus was first reported in 2007 by British paleontologist Phil Manning, from the Hell Creek Formation of Montana. This second track measures 76 centimetres (30 in) long, shorter than the track described by Lockley and Hunt. Whether or not the track was made by Tyrannosaurus is unclear, though Tyrannosaurus and Nanotyrannus are the only large theropods known to have existed in the Hell Creek Formation. Further study of the track (a full description has not yet been published) will compare the Montana track with the one found in New Mexico.[55]

Locomotion

File:Sauropod tracks.png

A sequence of sauropod footprints. No such sequence has yet been reported for tyrannosaurs, making gait and speed estimates difficult.

T.rex

Foot of a Tyrannosaurus rex.

There are two main issues concerning the locomotory abilities of Tyrannosaurus: how well it could turn; and what its maximum straight-line speed was likely to have been. Both are relevant to the debate about whether it was a hunter or a scavenger (see below).

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.[56] The cause of the difficulty is rotational inertia, since much of Tyrannosaurus’ mass was some distance from its center of gravity, like a human carrying a heavy timber—although it might have reduced the average distance by arching its back and tail and pulling its head and forelimbs close to its body, rather like the way ice skaters pull their arms closer in order to spin faster.[57]

Scientists have produced a wide range of maximum speed estimates, mostly around 11 metres per second (25 mph), but a few as low as 5–11 metres per second (11–25 mph), and a few as high as 20 metres per second (45 mph). Researchers have to rely on various estimating techniques because, while there are many 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.[58] Scientists who think that Tyrannosaurus was able to run point out that hollow bones and other features that would have lightened its body may have kept adult weight to a mere 5 tons or so, or that other animals like ostriches and horses with long, flexible legs are able to achieve high speeds through slower but longer strides. Additionally, some have argued that Tyrannosaurus had relatively larger leg muscles than any animal alive today, which could have enabled fast running 40–70 kilometres per hour (25–43 mph).[59]

Jack Horner and Don Lessem argued in 1993 that Tyrannosaurus was slow and probably could not run (no airborne phase in mid-stride), because its ratio of femur (thigh bone) to tibia (shin bone) length was greater than 1, as in most large theropods and like a modern elephant.[34] However, Holtz (1998) noted that tyrannosaurids and some closely related groups had significantly longer distal hindlimb components (shin plus foot plus toes) relative to the femur length than most other theropods), and that tyrannosaurids and their close relatives had a tightly interlocked metatarsus that more effectively transmitted locomotory forces from the foot to the lower leg than in earlier theropods ("metatarsus" means the foot bones, which function as part of the leg in digitigrade animals). He therefore concluded that tyrannosaurids and their close relatives were the fastest large theropods.[60]

T-rex Leg Bone structures

Skeletal anatomy of a T. rex right leg.

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 11 metres per second (25 mph), which is about the speed of a human sprinter. But he also noted that such estimates depend on many dubious assumptions.[61]

Farlow and colleagues (1995) have argued that a 6 short tons (5.4 t) to 8 short tons (7.3 t) 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 g (six times the acceleration due to gravity, or about 60 meters/s²) and its tiny arms could not have reduced the impact.[7][62] However, giraffes have been known to gallop at 50 kilometres per hour (31 mph), despite the risk that they might break a leg or worse, which can be fatal even in a "safe" environment such as a zoo.[63][64] Thus it is quite possible that Tyrannosaurus also moved fast when necessary and had to accept such risks.[65][66]

Most recent research on Tyrannosaurus locomotion does not narrow down speeds further than a range from 17 to 40 kilometres per hour (11 to 25 mph), i.e. from walking or slow running to moderate-speed running. For example, a 2002 paper in the journal Nature used a mathematical model (validated by applying it to three living animals, [alligators, chickens, and humans; additionally later eight more species including emus and ostriches[67]) to gauge the leg muscle mass needed for fast running (over 40 kilometres per hour (25 mph)).[59] They found that proposed top speeds in excess of 40 kilometres per hour (25 mph) were unfeasible, because they would require very large leg muscles (more than approximately 40–86% of total body mass.) Even moderately fast speeds would have required large leg muscles. This discussion is difficult to resolve, as it is unknown how large the leg muscles actually were in Tyrannosaurus. If they were smaller, only 18 kilometres per hour (11 mph) walking/jogging might have been possible.[59]

A study in 2007 used computer models to estimate running speeds, based on data taken directly from fossils, and claimed that T. rex had a top running speed of 8 metres per second (18 mph). An average professional football (soccer) player would be slightly slower, while a human sprinter can reach 12 metres per second (27 mph). Note that these computer models predict a top speed of 17.8 metres per second (40 mph) for a 3 kilograms (6.6 lb) CompsognathusCite error: Invalid <ref> tag; invalid names, e.g. too many[68] (probably a juvenile individual).[69]

Those who argue that Tyrannosaurus was incapable of running estimate the top speed of Tyrannosaurus at about 17 kilometres per hour (11 mph). This is still faster than its most likely prey species, hadrosaurids and ceratopsians.[59] In addition, some advocates of the idea that Tyrannosaurus was a predator claim that tyrannosaur running speed is not important, since it may have been slow but still faster than its probable prey.[70] However, Paul and Christiansen (2000) argued that at least the later ceratopsians had upright forelimbs and the larger species may have been as fast as rhinos.[71] Healed Tyrannosaurus bite wounds on ceratopsian fossils are interpreted as evidence of attacks on living ceratopsians (see below). If the ceratopsians that lived alongside Tyrannosaurus were fast, that casts doubt on the argument that Tyrannosaurus did not have to be fast to catch its prey.[66]

History

Tyrannosaurus skeleton

Skeletal restoration by William D. Matthew from 1905, which was the first reconstruction of Tyrannosaurus rex ever published[72]

Henry Fairfield Osborn, president of the American Museum of Natural History, named Tyrannosaurus rex in 1905. The generic name is derived from the Greek words τυραννος (tyrannos, meaning "tyrant") and σαυρος (sauros, meaning "lizard"). Osborn used the Latin word rex, meaning "king", for the specific name. The full binomial therefore translates to "tyrant lizard king," emphasizing the animal's size and perceived dominance over other species of the time.[31]

Earliest finds

Teeth from what is now documented as a T. rex were found in 1874 by A. Lakes near Golden, Colorado. In the early 1890s, J. B. Hatcher collected postcranial elements in eastern Wyoming. The fossils were believed to be from a large species of Ornithomimus (O. grandis) but are now considered T. rex. Vertebral fragments found by E. D. Cope in western South Dakota in 1892 and named as Manospondylus gigas have also been reclassified as T. rex.[12]

File:T.rex mount.png

Scale model of the never-completed Tyrannosaurus rex exhibit planned for the American Museum of Natural History, by H.F. Osborn.

Barnum Brown, assistant curator of the American Museum of Natural History, found the first partial skeleton of T. rex in eastern Wyoming in 1900. H. F. Osborn originally named this skeleton Dynamosaurus imperiosus in a paper in 1905. Brown found another partial skeleton in the Hell Creek Formation in Montana in 1902. Osborn used this holotype to describe Tyrannosaurus rex in the same paper in which D. imperiosus was described.[73] Had it not been for page order, Dynamosaurus would have become the official name. The original Dynamosaurus material resides in the collections of the Natural History Museum, in London.[74]

In total, Brown found five Tyrannosaurus partial skeletons. In 1941, Brown's 1902 find was sold to the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. Brown's fourth and largest find, also from Hell Creek, is on display in the American Museum of Natural History, in New York.[34]

Although there are numerous skeletons in the world, only one track has been documented — at Philmont Scout Ranch in northeast New Mexico. It was discovered in 1983 and identified and documented in 1994.[75]

Notable specimens

Sue, at the FMoNH

"Sue" the Tyrannosaurus, Field Museum of Natural History, Chicago, showing the forelimbs. The 'wishbone' is between the forelimbs.

Sue Hendrickson, amateur paleontologist, discovered the most complete (more than 90%) and, until 2001, the largest, Tyrannosaurus fossil skeleton known in the Hell Creek Formation near Faith, South Dakota, on 12 August 1990. This Tyrannosaurus, nicknamed "Sue" in her honor, was the object of a legal battle over its ownership. In 1997 this was settled in favor of Maurice Williams, the original land owner, and the fossil collection was sold at auction for USD 7.6 million, making it the most expensive dinosaur skeleton to date. It has now been reassembled and is currently exhibited at the Field Museum of Natural History. A study of this specimen's fossilized bones showed that "Sue" reached full size at age 19 and died at age 28, the longest any tyrannosaur is known to have lived.[76] The "Sue" specimen apparently died from a massive bite to the head, which could only have been inflicted by another tyrannosaur.[77]

Another Tyrannosaurus, nicknamed "Stan", in honor of amateur paleontologist Stan Sacrison, was found in the Hell Creek Formation near Buffalo, South Dakota, in the spring of 1987. After 30,000 hours of digging and preparing, a 65% complete skeleton emerged. Stan is currently on display in the Black Hills Museum of Natural History Exhibit in Hill City, South Dakota, after an extensive world tour. This tyrannosaur, too, was found to have many bone pathologies, including broken and healed ribs, a broken (and healed) neck and a spectacular hole in the back of its head, about the size of a Tyrannosaurus tooth. Both Stan and Sue were examined by Peter Larson.

In the summer of 2000, Jack Horner discovered five Tyrannosaurus skeletons near the Fort Peck Reservoir in Montana. One of the specimens, dubbed "C. rex," was reported to be perhaps the largest Tyrannosaurus ever found.[78]

Tyrannosaurus Jane

"Jane" at the Burpee Museum in Rockford, Illinois.

In 2001, a 50% complete skeleton of a juvenile Tyrannosaurus was discovered in the Hell Creek Formation in Montana, by a crew from the Burpee Museum of Natural History of Rockford, Illinois. Dubbed "Jane the Rockford T-Rex," the find was initially considered the first known skeleton of the pygmy tyrannosaurid Nanotyrannus but subsequent research has revealed that it is more likely a juvenile Tyrannosaurus.[79] It is the most complete and best preserved juvenile example known to date. Jane has been examined by Jack Horner, Pete Larson, Robert Bakker, Greg Erickson and several other renowned paleontologists, because of the uniqueness of her age. Jane is currently on exhibit at the Burpee Museum of Natural History in Rockford, Illinois.[80][81]

In a press release on 7 April 2006, Montana State University revealed that it possessed the largest Tyrannosaurus skull yet discovered. Discovered in the 1960s and only recently reconstructed, the skull measures 59 inches (150 cm) long compared to the 55.4 inches (141 cm) of “Sue’s” skull, a difference of 6.5%.[82][83]

Cultural Influence

Since it was first described in 1905, Tyrannosaurus rex has become the most widely recognized dinosaur in popular culture. It is the only dinosaur which is routinely referred to by its full scientific name (Tyrannosaurus rex) among the general public, and the scientific abbreviation T. rex has also come into wide usage (commonly misspelled "T-Rex").[1] Robert T. Bakker notes this in The Dinosaur Heresies and explains that a name like "Tyrannosaurus rex is just irresistible to the tongue."[6]

Museum exhibits featuring T. rex are very popular; an estimated 10,000 visitors flocked to Chicago's Field Museum on the opening day of its "Sue" exhibit in 2003.[84] T. rex has appeared numerous times on television and in films, notably (in chronological order) The Lost World, King Kong, The Land Before Time, the Jurassic Park films, Barney and Friends, Toy Story, Toy Story 2, Walking with Dinosaurs, and Night at the Museum, among many others. A number of books and comic strips, including Calvin and Hobbes and Dinosaur Comics, have also featured Tyrannosaurus, which is typically portrayed as the biggest and most terrifying carnivore of all. At least one musical group, the band T.Rex, is named after the species. Tyrannosaurus-related toys, including numerous video games and other merchandise, remain popular. Various businesses have capitalized on the popularity of Tyrannosaurus rex by using it in advertisements.

General Impact

Tyrannosaurus rex is unique among dinosaurs in its place in modern culture; paleontologist Robert Bakker has called it "the most popular dinosaur among people of all ages, all cultures, and all nationalities".[85] From the beginning, it was embraced by the public. Henry Fairfield Osborn billed it the greatest hunter to have ever walked the earth. He stated in 1905,[86]

I propose to make this animal the type of the new genus, Tyrannosaurus, in reference to its size, which far exceeds that of any carnivorous land animal hitherto described...This animals is in fact the ne plus ultra of the evolution of the large carnivorous dinosaurs: in brief it is entitled to the royal and high sounding group name which I have applied to it.


Tyrannosaurus gained widespread public attention on December 30, 1905, when the New York Times hailed T. rex as "the most formidable fighting animal of which there is any record whatever," the "king of all kings in the domain of animal life," "the absolute warlord of the earth," and a "royal man-eater of the jungle." [87] In 1906, Tyrannosaurus was dubbed the "prize fighter of antiquity" and the "Last of the Great Reptiles and the King of Them All."[88]

In 1942, Charles R. Knight painted a mural incorporating Tyrannosaurus facing a Triceratops in the Field Museum of Natural History for the National Geographic Society, establishing the two dinosaurs as enemies in popular thought;[89] paleontologist Phil Currie cites this mural as one of his inspirations to study dinosaurs.[86] Bakker said of the imagined rivalry between Tyrannosaurus and Triceratops, "No matchup between predator and prey has ever been more dramatic. It’s somehow fitting that those two massive antagonists lived out their co-evolutionary belligerence through the very last days of the very last epoch of the Age of Dinosaurs."[89]

References

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