Editing Allosaurus (section)

===Feeding===
[[File:Steg Bitten Plate.jpg|thumb|left|Bitten ''Stegosaurus'' plate close-up, showing how well the damage matches the front of an ''Allosaurus'' "mouth"]]
Most paleontologists accept ''Allosaurus'' as an active predator of large animals. There is dramatic evidence for allosaur attacks on ''Stegosaurus'', including an ''Allosaurus'' tail vertebra with a partially healed puncture wound that fits a ''Stegosaurus'' [[Thagomizer|tail spike]], and a ''Stegosaurus'' neck plate with a U-shaped wound that correlates well with an ''Allosaurus'' snout.<ref name=KSMW05>{{cite book |first1=Kenneth |last1=Carpenter |last2=Sanders, Frank|last3= McWhinney, Lorrie A.|last4= Wood, Lowell |title=The Carnivorous Dinosaurs|year=2005 |chapter=Evidence for predator-prey relationships: Examples for ''Allosaurus'' and ''Stegosaurus'' |editor=Carpenter, Kenneth |pages=325–350 |publisher=Indiana University Press |location=Bloomington and Indianapolis |isbn= 978-0-253-34539-4 }}</ref> [[Sauropod]]s seem to be likely candidates as both live prey and as objects of [[Scavenger|scavenging]], based on the presence of scrapings on sauropod bones fitting allosaur teeth well and the presence of shed allosaur teeth with sauropod bones.<ref name=FS04>Fastovsky, David E.; and Smith, Joshua B. (2004). "Dinosaur Paleoecology", in ''The Dinosauria'' (2nd ed.). 614–626.</ref> However, as Gregory Paul noted in 1988, ''Allosaurus'' was probably not a predator of fully grown sauropods, unless it hunted in packs, as it had a modestly sized skull and relatively small teeth, and was greatly outweighed by contemporaneous sauropods.<ref name=GSP88/> Another possibility is that it preferred to hunt juveniles instead of fully grown adults.<ref name=LG93/><ref name=JF07/> Research in the 1990s and the first decade of the 21st century may have found other solutions to this question. [[Robert T. Bakker]], comparing ''Allosaurus'' to [[Cenozoic]] saber-toothed carnivorous mammals, found similar adaptations, such as a reduction of jaw muscles and increase in neck muscles, and the ability to open the jaws extremely wide. Although ''Allosaurus'' did not have saber teeth, Bakker suggested another mode of attack that would have used such neck and jaw adaptations: the short teeth in effect became small serrations on a [[saw]]-like cutting edge running the length of the upper jaw, which would have been driven into prey. This type of jaw would permit slashing attacks against much larger prey, with the goal of weakening the victim.<ref name=BB98/>
[[File:Allosaurus Jaws Steveoc86.jpg|thumb|''A. fragilis'' showing its maximum possible gape, based on [[Robert T. Bakker|Bakker]] (1998) and [[Emily Rayfield|Rayfield]] et al. (2001)]]
Similar conclusions were drawn by another study using [[finite element analysis]] on an ''Allosaurus'' skull. According to their biomechanical analysis, the skull was very strong but had a relatively small bite force. By using jaw muscles only, it could produce a bite force of 805 to 8,724 [[Newton (unit)|N]],<ref name=ERetal01/><ref name="BatesFalkingham2012">{{Cite journal|last1=Bates|first1=K. T.|last2=Falkingham|first2=P.L.|date=February 29, 2012|title=Estimating maximum bite performance in ''Tyrannosaurus rex'' using multi-body dynamics|journal=Biology Letters|volume=8|issue=4|pages=660–664|doi=10.1098/rsbl.2012.0056|pmid=22378742|pmc=3391458}}</ref> but the skull could withstand nearly 55,500 N of vertical force against the tooth row.<ref name=ERetal01/> The authors suggested that ''Allosaurus'' used its skull like a machete against prey, attacking open-mouthed, slashing flesh with its teeth, and tearing it away without splintering bones, unlike ''Tyrannosaurus'', which is thought to have been capable of damaging bones. They also suggested that the architecture of the skull could have permitted the use of different strategies against different prey; the skull was light enough to allow attacks on smaller and more agile ornithopods, but strong enough for high-impact ambush attacks against larger prey like stegosaurids and sauropods.<ref name=ERetal01/> Their interpretations were challenged by other researchers, who found no modern analogs to a hatchet attack and considered it more likely that the skull was strong to compensate for its open construction when absorbing the stresses from struggling prey.<ref name=FK02>{{cite journal |last1=Frazzetta |first1=T. H. |year=2002 |title=Prey attack by a large theropod dinosaur |journal=Nature |volume=416 |pages=387–388 |doi=10.1038/416387a |pmid=11919619 |last2=Kardong |first2=K. V. |issue=6879|bibcode = 2002Natur.416..387F |s2cid=4388901 }}</ref> The original authors noted that ''Allosaurus'' itself has no modern equivalent, that the tooth row is well-suited to such an attack, and that articulations in the skull cited by their detractors as problematic actually helped protect the [[palate]] and lessen stress.<ref name=ERetal02>{{cite journal |last1=Rayfield |first1=Emily J. |year=2002 |title=Prey attack by a large theropod dinosaur: Response to Frazzetta and Kardong, 2002 |journal=Nature |volume=416 |page=388 |doi=10.1038/416388a |last2=Norman |first2=D. B. |last3=Upchurch |first3=P. |issue=6879|bibcode = 2002Natur.416..388R |s2cid=4392259 |doi-access=free }}</ref> Another possibility for handling large prey is that theropods like ''Allosaurus'' were "flesh grazers" which could take bites of flesh out of living sauropods that were sufficient to sustain the predator so it would not have needed to expend the effort to kill the prey outright. This strategy would also potentially have allowed the prey to recover and be fed upon in a similar way later.<ref name=HMC04/> An additional suggestion notes that ornithopods were the most common available dinosaurian prey, and that ''Allosaurus'' may have subdued them by using an attack similar to that of modern big cats: grasping the prey with their forelimbs, and then making multiple bites on the throat to crush the trachea.<ref name=JF07/> This is compatible with other evidence that the forelimbs were strong and capable of restraining prey.<ref name=KC02/> Studies done by Stephen Lautenschager et al. from the University of Bristol also indicate ''Allosaurus'' could open its jaws quite wide and sustain considerable muscle force. When compared with ''Tyrannosaurus'' and the therizinosaurid ''[[Erlikosaurus]]'' in the same study, it was found that ''Allosaurus'' had a wider gape than either; the animal was capable of opening its jaws to a 92-degree angle at maximum. The findings also indicate that large carnivorous dinosaurs, like modern carnivores, had wider jaw gapes than herbivores.<ref>{{cite journal |last=Lautenschlager |first= Stephan |title= Estimating cranial musculoskeletal constraints in theropod dinosaurs |volume= 2 |issue= 11 |pages= 150495 |journal= Royal Society Open Science|date=November 4, 2015 |doi= 10.1098/rsos.150495 |pmid= 26716007 |pmc= 4680622 |bibcode= 2015RSOS....250495L }}</ref><ref>{{cite web |url=https://www.sciencedaily.com/releases/2015/11/151103213705.htm |title= Better to eat you with? How dinosaurs' jaws influenced diet |date=November 3, 2015 |work=Science Daily |url-status=live |archive-url=https://web.archive.org/web/20160307232743/https://www.sciencedaily.com/releases/2015/11/151103213705.htm |archive-date=March 7, 2016}}</ref>

[[File:Denver Museum new Allosaurus skull vs Stegosaurus.jpg|left|thumb|''Allosaurus'' and ''Stegosaurus'' skeletons, the [[Denver Museum of Nature and Science]]]]
A [[Biomechanics|biomechanical]] study published in 2013 by Eric Snively and colleagues found that ''Allosaurus'' had an unusually low attachment point on the skull for the [[Longissimus#Longissimus capitis|longissimus capitis superficialis]] neck muscle compared to other theropods such as ''[[Tyrannosaurus]]''. This would have allowed the animal to make rapid and forceful vertical movements with the skull. The authors found that vertical strikes as proposed by Bakker and Rayfield are consistent with the animal's capabilities. They also found that the animal probably processed carcasses by vertical movements in a similar manner to [[falcon]]s, such as [[kestrel]]s: The animal could have gripped prey with the skull and feet, then pulled back and up to remove flesh. This differs from the prey-handling envisioned for tyrannosaurids, which probably tore flesh with lateral shakes of the skull, similar to crocodilians.<ref name=ESetal2013>{{cite journal |last1=Snively |first1=Eric. |last2=Cotton, John R.|last3= Ridgely, Ryan|last4= Witmer, Lawrence M. |year=2013 |title=Multibody dynamics model of head and neck function in ''Allosaurus'' (Dinosauria, Theropoda) |journal=Palaeontologia Electronica |volume=16 |issue=2 |page=338 |doi=10.26879/338 |doi-access=free |bibcode=2013PalEl..16..338S }}</ref> In addition, ''Allosaurus'' was able to "move its head and neck around relatively rapidly and with considerable control", at the cost of power.<ref name=Scidaily2013>{{cite web|last=Ohio University|title=Allosaurus fed more like a falcon than a crocodile: Engineering, anatomy work reveals differences in dinosaur feeding styles|url=https://www.sciencedaily.com/releases/2013/05/130521152638.htm|website=ScienceDaily|access-date=May 22, 2013|date=May 22, 2013|archive-date=November 9, 2021|archive-url=https://web.archive.org/web/20211109005339/https://www.sciencedaily.com/releases/2013/05/130521152638.htm|url-status=live}}</ref>

Other aspects of feeding include the eyes, arms, and legs. The shape of the skull of ''Allosaurus'' limited potential [[binocular vision]] to 20° of width, slightly less than that of modern [[crocodilia]]ns. As with crocodilians, this may have been enough to judge prey distance and time attacks.<ref>{{cite journal |last1=Rogers |first1=Scott W. |title=Reconstructing the behaviors of extinct species: An excursion into comparative paleoneurology |journal=American Journal of Medical Genetics Part A |date=March 9, 2005 |volume=134A |issue=4 |pages=349–356 |doi=10.1002/ajmg.a.30538 |pmid=15759265 |url=https://onlinelibrary.wiley.com/doi/10.1002/ajmg.a.30538 |language=en |issn=1552-4825}}</ref><ref>{{Cite journal |last=Rogers |first=Scott W. |date=October 15, 1999 |title=Allosaurus, crocodiles, and birds: Evolutionary clues from spiral computed tomography of an endocast |url=https://onlinelibrary.wiley.com/doi/10.1002/(SICI)1097-0185(19991015)257:53.0.CO;2-W |journal=The Anatomical Record |language=en |volume=257 |issue=5 |pages=162–173 |doi=10.1002/(SICI)1097-0185(19991015)257:5<162::AID-AR5>3.0.CO;2-W |pmid=10597341 |issn=0003-276X}}</ref><ref name=KAS06>{{cite journal |last=Stevens |first=Kent A. |year=2006 |title=Binocular vision in theropod dinosaurs |journal=Journal of Vertebrate Paleontology |volume=26 |issue=2 |pages=321–330 |doi=10.1671/0272-4634(2006)26[321:BVITD]2.0.CO;2 |s2cid=85694979 |issn=0272-4634 }}</ref> The arms, compared with those of other theropods, were suited for both grasping prey at a distance or clutching it close,<ref name=KC02/> and the articulation of the claws suggests that they could have been used to hook things.<ref name=CWG20/> Finally, the top speed of ''Allosaurus'' has been estimated at {{cvt|30|-|55|km}} per hour.<ref name=PC98>{{cite journal |last=Christiansen |first=Per |year=1998 |title=Strength indicator values of theropod long bones, with comments on limb proportions and cursorial potential |journal=Gaia |volume=15 |pages=241–255 |issn=0871-5424}}</ref>

A paper on the cranio-dental morphology of ''Allosaurus'' and how it worked has deemed the hatchet jaw attack unlikely, reinterpreting the unusually wide gape as an adaptation to allow ''Allosaurus'' to deliver a muscle-driven bite to large prey, with the weaker jaw muscles being a trade-off to allow for the widened gape.<ref>{{cite journal|url=http://digital.csic.es/bitstream/10261/22490/1/102.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://digital.csic.es/bitstream/10261/22490/1/102.pdf |archive-date=October 9, 2022 |url-status=live|last1=Anton|first1=M.|last2=Sánchez|first2=I.|last3=Salesa|first3=Manuel|last4=Turner|first4=A|year=2003|title=The muscle-powered bite of ''Allosaurus'' (Dinosauria; Theropoda): An interpretation of cranio-dental morphology.|journal=Estudios Geológicos|volume=59|issue=5|pages=313–323|doi=10.3989/egeol.03595-6106}}</ref>

[[File:Barosaurus lentus1.jpg|thumb|right|Restoration of ''[[Barosaurus]]'' rearing to defend itself against a pair of ''A. fragilis'']]
Sauropod carrion may also have been important to large theropods in the Morrison Formation. Forensic techniques indicate that sauropod carcasses were targeted by ''Allosaurus'' at all stages of decomposition, indicating that late-stage decay pathogens were not a significant deterrent.<ref>{{Cite journal |last1=Bader |first1=Kenneth |last2=Hasiotis |first2=Stephen |year=2009 |title=Application of forensic science techniques to trace fossils on dinosaur bones from a quarry in the Upper Jurassic Morrison Formation, Northeastern Wyoming |url=https://doi.org/10.2110/palo.2008.p08-058r |access-date=January 17, 2024 |journal=PALAIOS |volume=24 |issue=3 |pages=140–158 |language=en |publication-place=PALAIOS |doi=10.2110/palo.2008.p08-058r|bibcode=2009Palai..24..140B }}</ref><ref>{{cite journal |last1=Storrs |first1=Glenn W. |last2=Oser |first2=Sara E. |last3=Aull |first3=Mark |title=Further analysis of a Late Jurassic dinosaur bone-bed from the Morrison Formation of Montana, USA, with a computed three-dimensional reconstruction |journal=Earth and Environmental Science Transactions of the Royal Society of Edinburgh |date=September 23, 2013 |volume=103 |issue=3–4 |pages=443–458 |doi=10.1017/S1755691013000248 |url=https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/abs/further-analysis-of-a-late-jurassic-dinosaur-bonebed-from-the-morrison-formation-of-montana-usa-with-a-computed-threedimensional-reconstruction/7539F3414CA4B031A33C115C94A2C954 |issn=1755-6910 |archive-date=January 17, 2024 |access-date=January 17, 2024 |archive-url=https://web.archive.org/web/20240117201743/https://www.cambridge.org/core/journals/earth-and-environmental-science-transactions-of-royal-society-of-edinburgh/article/abs/further-analysis-of-a-late-jurassic-dinosaur-bonebed-from-the-morrison-formation-of-montana-usa-with-a-computed-threedimensional-reconstruction/7539F3414CA4B031A33C115C94A2C954 |url-status=live }}</ref> A survey of sauropod bones from the Morrison Formation also reported widespread bite marks on sauropod bones in low-economy regions, which suggests that large theropods scavenged large sauropods when available, with the scarcity of such bite marks on the remains of smaller bones being potentially attributable to much more complete consumption of smaller or adolescent sauropods and on ornithischians, which would have been more commonly taken as live prey.<ref name="ReferenceA"/><ref>{{Cite journal |last1=Lei |first1=Roberto |last2=Tschopp |first2=Emanuel |last3=Hendrickx |first3=Christophe |last4=Wedel |first4=Mathew J. |last5=Norell |first5=Mark |last6=Hone |first6=David W. E. |date=November 14, 2023 |title=Bite and tooth marks on sauropod dinosaurs from the Morrison Formation |journal=PeerJ |language=en |volume=11 |pages=e16327 |doi=10.7717/peerj.16327 |doi-access=free |pmid=38025762 |pmc=10655710 |issn=2167-8359}}</ref> A single dead adult ''Barosaurus'' or ''Brachiosaurus'' would have had enough calories to sustain multiple large theropods for weeks or months,<ref>{{Cite journal |last1=Pahl |first1=Cameron C. |last2=Ruedas |first2=Luis A. |date=October 15, 2021 |title=Carnosaurs as Apex Scavengers: Agent-based simulations reveal possible vulture analogues in late Jurassic Dinosaurs |url=https://www.sciencedirect.com/science/article/pii/S0304380021002611 |journal=Ecological Modelling |volume=458 |pages=109706 |doi=10.1016/j.ecolmodel.2021.109706 |bibcode=2021EcMod.45809706P |issn=0304-3800}}</ref> though the vast majority of the Morrison's sauropod fossil record consisted of much smaller-bodied taxa such as ''Camarasaurus lentus'' or ''Diplodocus''.<ref name="Foster">{{cite book |last=Foster |first=John |author-link= |date=October 20, 2020 |title=Jurassic West, Second Addition: The Dinosaurs of the Morrison Formation and Their World  |url= https://iupress.org/9780253051578/jurassic-west-second-edition/ |location= |publisher=Indiana University Press |page= |isbn= 9780253051578}}</ref>

It has also been argued that disabled individuals such as Big Al and Big Al II were physically incapable of hunting due to their numerous injuries but were able to survive nonetheless as scavengers of giant sauropod-falls,<ref>{{Cite journal |last1=Pahl |first1=Cameron C. |last2=Ruedas |first2=Luis A. |date=March 1, 2023 |title=''Allosaurus'' was predominantly a scavenger |url=https://www.sciencedirect.com/science/article/pii/S0304380022003593 |journal=Ecological Modelling |volume=477 |pages=110261 |doi=10.1016/j.ecolmodel.2022.110261 |bibcode=2023EcMod.47710261P |issn=0304-3800}}</ref> Interestingly, a recent review of paleopathologies in theropods may support this conclusion. The researchers found a positive association between allosaurids and fractures to the appendicular skeleton, while tyrannosaurs had a statistically negative association with these types of injuries.<ref>{{Cite journal |last1=Baiano |first1=Mattia A. |last2=Cerda |first2=Ignacio A. |last3=Bertozzo |first3=Filippo |last4=Pol |first4=Diego |date=January 31, 2024 |title=New information on paleopathologies in non-avian theropod dinosaurs: a case study on South American abelisaurids |journal=BMC Ecology and Evolution |volume=24 |issue=1 |pages=6 |doi=10.1186/s12862-023-02187-x |doi-access=free |issn=2730-7182 |pmc=10829224 |pmid=38291378|bibcode=2024BMCEE..24....6B }}</ref> The fact that allosaurs were more likely to survive and heal even when severe fractures limited their locomotion abilities can be explained, in part, by different resource accessibility paradigms for the two groups, as allosauroids generally lived in sauropod-inhabited ecosystems, some of which, including the Morrison, have been interpreted as arid and highly water-stressed environments; however, the water-stressed nature of the Morrison has been heavily criticized in several more recent works on the basis of fossil evidence for the presence of extensive forest cover and aquatic ecosystems.<ref name="Foster"/>