Editing Tyrannosaurus (section)

===Speed===
{{Annotated image/Skeletal anatomy of T rex right leg | float=left}}
Scientists have produced a wide range of possible maximum running speeds for ''Tyrannosaurus'': mostly around {{convert|9|m/s|km/h mph|sp=us}}, but as low as {{convert|4.5|–|6.8|m/s|km/h mph|sp=us}} and as high as {{convert|20|m/s|km/h mph|sp=us}}, though it running this speed is very unlikely. ''Tyrannosaurus'' was a bulky and heavy carnivore so it is unlikely to run very fast at all compared to other theropods like ''[[Carnotaurus]]'' or ''[[Giganotosaurus]]''.<ref name="HutchinsonGarcia2002TrexSlow">{{Cite journal |last1=Hutchinson |first1=J. R. |last2=Garcia |first2=M. |s2cid=4389633 |date=2002 |title=''Tyrannosaurus'' was not a fast runner |journal=Nature |volume=415 |issue=6875 |pages=1018–21 |bibcode=2002Natur.415.1018H |doi=10.1038/4151018a |pmid=11875567 |url=http://researchonline.rvc.ac.uk/id/eprint/1204/ |archive-date=August 9, 2022 |access-date=January 23, 2023 |archive-url=https://web.archive.org/web/20220809012102/https://researchonline.rvc.ac.uk/id/eprint/1204/ |url-status=live }}</ref> Researchers have relied on various estimating techniques because, while there are many [[trackway|tracks]] of large theropods walking, none showed evidence of running.<ref name="Hutchinson2004">{{Cite journal |last=Hutchinson |first=J. R. |year=2004 |title=Biomechanical Modeling and Sensitivity Analysis of Bipedal Running Ability. II. Extinct Taxa |url=http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf  |journal=Journal of Morphology |volume=262 |issue=1 |pages=441–461 |doi=10.1002/jmor.10240 |pmid=15352202 |s2cid=15677774 |archive-url=https://web.archive.org/web/20081031093050/http://www.rvc.ac.uk/AboutUs/Staff/jhutchinson/documents/JRH13.pdf |archive-date=October 31, 2008}}</ref>

A 2002 report used a mathematical model (validated by applying it to three living animals: [[alligator]]s, [[chicken]]s, and [[human]]s; and eight more species, including emus and ostriches<ref name="Hutchinson2004" />) to gauge the leg muscle mass needed for fast running (over {{convert|40|km/h|mph|disp=or|abbr=on}}).<ref name="HutchinsonGarcia2002TrexSlow" /> 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 {{convert|4.5|MT|ST}} or so, or that other animals like [[ostrich]]es and [[horse]]s with long, flexible legs are able to achieve high speeds through slower but longer strides.<ref name="Hutchinson2004" /> Proposed top speeds exceeded {{convert|40|km/h|mph|sp=us}} for ''Tyrannosaurus'', but were deemed infeasible because they would require exceptional leg muscles of approximately 40–86%&nbsp;of total body mass. Even moderately fast speeds would have required large leg muscles. If the muscle mass was less, only {{convert|18|km/h|mph|sp=us}} for walking or jogging would have been possible.<ref name="HutchinsonGarcia2002TrexSlow" /> Holtz 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]] (foot bones).<ref name="Holtz1998TaxonomyCoelurosauria">{{Cite journal |last=Holtz |first=T. R. |author-link=Thomas R. Holtz Jr. |date=May 1, 1996 |title=Phylogenetic taxonomy of the Coelurosauria (Dinosauria; Theropoda) |url=http://jpaleontol.geoscienceworld.org/cgi/content/abstract/70/3/536 |journal=[[Journal of Paleontology]] |volume=70 |issue=3 |pages=536–538 |doi=10.1017/S0022336000038506 |bibcode=1996JPal...70..536H |s2cid=87599102 |access-date=October 3, 2008 |archive-date=October 26, 2008 |archive-url=https://web.archive.org/web/20081026053239/http://jpaleontol.geoscienceworld.org/cgi/content/abstract/70/3/536 |url-status=live }}</ref> The third metatarsal was squeezed between the second and fourth metatarsals to form a single unit called an [[arctometatarsal|arctometatarsus]]. This ankle feature may have helped the animal to run more efficiently.<ref>{{Cite book |url=https://books.google.com/books?id=VThUUUtM8A4C&q=tyrannosaurus+metatarsals+squeezing&pg=PA193 |title=Vertebrate Palaeontology |last=Benton |first=M. |year=2014 |isbn=978-1-118-40755-4 |edition=4th |page=193|publisher=John Wiley & Sons }}</ref> Together, these leg features allowed ''Tyrannosaurus'' to transmit locomotory forces from the foot to the lower leg more effectively than in earlier theropods.<ref name="Holtz1998TaxonomyCoelurosauria" />  
[[File:Tyrannosaurid trackway.png|thumb|Only known tyrannosaurid trackway (''[[Bellatoripes fredlundi]]''), from the [[Wapiti Formation]], [[British Columbia]]]]

Additionally, a 2020 study indicates that ''Tyrannosaurus'' and other tyrannosaurids were exceptionally efficient walkers. Studies by Dececchi et al., compared the leg proportions, body mass, and the gaits of more than 70 species of theropod dinosaurs including ''Tyrannosaurus'' and its relatives. The research team then applied a variety of methods to estimate each dinosaur's top speed when running as well as how much energy each dinosaur expended while moving at more relaxed speeds such as when walking. Among smaller to medium-sized species such as dromaeosaurids, longer legs appear to be an adaptation for faster running, in line with previous results by other researchers. But for theropods weighing over {{convert|1000|kg|lb|abbr=on}}, top running speed is limited by body size, so longer legs instead were found to have correlated with low-energy walking. The results further indicate that smaller theropods evolved long legs as a means to both aid in hunting and escape from larger predators while larger theropods that evolved long legs did so to reduce the energy costs and increase foraging efficiency, as they were freed from the demands of predation pressure due to their role as apex predators. Compared to more basal groups of theropods in the study, tyrannosaurs like ''Tyrannosaurus'' itself showed a marked increase in foraging efficiency due to reduced energy expenditures during hunting or scavenging. This in turn likely resulted in tyrannosaurs having a reduced need for hunting forays and requiring less food to sustain themselves as a result. Additionally, the research, in conjunction with studies that show tyrannosaurs were more agile than other large-bodied theropods, indicates they were quite well-adapted to a long-distance stalking approach followed by a quick burst of speed to go for the kill. Analogies can be noted between tyrannosaurids and modern wolves as a result, supported by evidence that at least some tyrannosaurids were hunting in group settings.<ref>{{Cite journal|title=The fast and the frugal: Divergent locomotory strategies drive limb lengthening in theropod dinosaurs |first1=T. Alexander |last1=Dececchi |first2=Aleksandra M. |last2=Mloszewska |first3=Thomas R. Jr. |last3=Holtz |first4=Michael B. |last4=Habib |first5=Hans C. E. |last5=Larsson |date=May 13, 2020 |journal=PLOS ONE |volume=15 |issue=5 |pages=e0223698 |doi=10.1371/journal.pone.0223698 |pmid=32401793 |pmc=7220109 |bibcode = 2020PLoSO..1523698D |doi-access=free}}</ref><ref>{{cite news |title=T. rex was a champion walker, super-efficient at lower speeds |url=https://www.eurekalert.org/news-releases/500578 |access-date=August 16, 2023 |work=EurekAlert! |date=May 13, 2020 |language=en |archive-date=August 16, 2023 |archive-url=https://web.archive.org/web/20230816101705/https://www.eurekalert.org/news-releases/500578 |url-status=live }}</ref>

A study published in 2021 by Pasha van Bijlert et al., calculated the [[preferred walking speed]] of ''Tyrannosaurus'', reporting a speed of {{convert|1.28|m/s|km/h mph|sp=us}}. While walking, animals reduce their [[cost of transport|energy expenditure]] by choosing certain step rhythms at which their body parts [[resonate]]. The same would have been true for [[dinosaurs]], but previous studies did not fully account for the impact the tail had on their walking speeds. According to the authors, when a dinosaur walked, its tail would slightly sway up and down with each step as a result of the [[interspinous ligaments]] suspending the tail. Like rubber bands, these ligaments stored energy when they are stretched due to the swaying of the tail. Using a 3-D model of ''Tyrannosaurus'' specimen [[Trix (dinosaur)|Trix]], muscles and ligaments were reconstructed to simulate the tail movements. This results in a rhythmic, energy-efficient walking speed for ''Tyrannosaurus'' similar to that seen in living animals such as humans, ostriches and giraffes.<ref name=vanBijlert2021>{{cite journal |author1=van Bijlert, P. A. |author2=van Soest, A. J. K. |author3=Schulp, A. S. |title=Natural Frequency Method: estimating the preferred walking speed of ''Tyrannosaurus rex'' based on tail natural frequency. |journal=Royal Society Open Science |volume=8 |issue=4 |page=201441 |year=2021 |doi=10.1098/rsos.201441 |pmid=33996115 |pmc=8059583 |bibcode=2021RSOS....801441V |s2cid=233312053 |url=https://phys.org/news/2021-04-dinosaur-biomechanical-tyrannosaurus-rex-gait.html |archive-date=April 22, 2021 |access-date=April 22, 2021 |archive-url=https://web.archive.org/web/20210422224520/https://phys.org/news/2021-04-dinosaur-biomechanical-tyrannosaurus-rex-gait.html |url-status=live }}</ref>

A 2017 study estimated the top running speed of ''Tyrannosaurus'' as {{convert|17|mph|km/h|abbr=on}}, speculating that ''Tyrannosaurus'' exhausted its energy reserves long before reaching top speed, resulting in a parabola-like relationship between size and speed.<ref>{{Cite web |url=https://www.sciencedaily.com/releases/2017/07/170717115657.htm |title=Why ''Tyrannosaurus'' was a slow runner and why the largest are not always the fastest |date=July 17, 2017 |website=ScienceDaily |language=en |access-date=November 10, 2017 |archive-date=April 2, 2019 |archive-url=https://web.archive.org/web/20190402111657/https://www.sciencedaily.com/releases/2017/07/170717115657.htm |url-status=live }}</ref><ref>{{Cite journal |last1=Hirt |first1=M. R. |last2=Jetz |first2=W. |last3=Rall |first3=B. C. |last4=Brose |first4=U. |s2cid=425473 |date=2017 |title=A general scaling law reveals why the largest animals are not the fastest. |journal=Nature Ecology & Evolution |volume=1 |issue=8 |pages=1116–1122 |doi=10.1038/s41559-017-0241-4 |pmid=29046579|bibcode=2017NatEE...1.1116H }}</ref> Another 2017 study hypothesized that an adult ''Tyrannosaurus'' was incapable of running due to high skeletal loads. Using a calculated weight estimate of 7&nbsp;tons, the model showed that speeds above {{convert|11|mph|km/h|abbr=on}} would have probably shattered the leg bones of ''Tyrannosaurus''. The finding may mean that running was also not possible for other giant theropod dinosaurs like ''[[Giganotosaurus]]'', ''[[Mapusaurus]]'' and ''[[Acrocanthosaurus]]''.<ref>{{Cite journal |last1=Sellers |first1=W. I. |last2=Pond |first2=S. B. |last3=Brassey |first3=C. A. |last4=Manning |first4=P. L. |last5=Bates |first5=K. T. |date=July 18, 2017 |title=Investigating the running abilities of ''Tyrannosaurus rex'' using stress-constrained multibody dynamic analysis |journal=PeerJ |language=en |volume=5 |pages=e3420 |doi=10.7717/peerj.3420 |issn=2167-8359 |pmc=5518979 |pmid=28740745 |doi-access=free }}</ref>
However, studies by Eric Snively and colleagues'','' published in 2019 indicate that ''Tyrannosaurus'' and other tyrannosaurids were more maneuverable than allosauroids and other theropods of comparable size due to low rotational inertia compared to their body mass combined with large leg muscles. As a result, it is hypothesized that ''Tyrannosaurus'' was capable of making relatively quick turns and could likely pivot its body more quickly when close to its prey, or that while turning, the theropod could "pirouette" on a single planted foot while the alternating leg was held out in a suspended swing during a pursuit. The results of this study potentially could shed light on how agility could have contributed to the success of tyrannosaurid evolution.<ref>{{Cite journal |last1=Cotton |first1=J. R. |last2=Hartman |first2=S. A. |last3=Currie |first3=P. J. |last4=Witmer |first4=L. M. |last5=Russell |first5=A. P. |last6=Holtz |first6=T. R. Jr. |last7=Burns |first7=M. E. |last8=Surring |first8=L. A. |last9=Mallison |first9=H. |date=February 21, 2019 |title=Lower rotational inertia and larger leg muscles indicate more rapid turns in tyrannosaurids than in other large theropods |journal=PeerJ |volume=7 |pages=e6432 |doi=10.7717/peerj.6432 |pmid=30809441 |pmc=6387760 |first10=D. M. |last10=Henderson |first11=H. |last11=O'Brien |first12=E. |last12=Snively |doi-access=free }}</ref>