Editing Gorgosaurus (section)

== Paleobiology ==

===Diet and feeding===

[[File:Gorgosaurus TMP 2009.12.14.jpg|thumb|''Gorgosaurus'' juvenile specimen TMP 2009.12.14, featuring stomach contents comprising remains of ''[[Citipes]]'']]
Just like other tyrannosaurids, bite force of ''Gorgosaurus'' and ''Albertosaurus'' increases slowly among young individuals, and then it increases exponentially when they reach the late juvenile stage.<ref name="TZVT21" /> In 2012, Jovannelly and Lane estimated that ''Gorgosaurus'' could exert a bite force of at least 22,000, possibly up to 42,000 newtons.<ref>{{cite journal |last1=Jovanelly |first1=Tamie J. |last2=Lane |first2=Lesley |title=Comparison of the Functional Morphology of Appalachiosaurus and Albertosaurus |journal=The Open Geology Journal |date=September 2012 |volume=6 |issue=1 |pages=65–71 |doi=10.2174/1874262901206010065|bibcode=2012OGJ.....6...65J |doi-access=free }}</ref> Other paleontologists have produced significantly lower bite force estimates. In 2021, given that the largest known ''Gorgosaurus'' had a similar bite force to the similar-sized ''Tyrannosaurus'', Therrien and colleagues proposed that the maximum bite force that could be produced by adult albertosaurines is around 12,200 to 21,800 newtons.<ref name="TZVT21">{{cite journal|author1=Therrien, F.|author2=Zelenitsky, D.K.|author3=Voris, J.T.|author4=Tanaka, K.|year=2021|title=Mandibular force profiles and tooth morphology in growth series of ''Albertosaurus sarcophagus'' and ''Gorgosaurus libratus'' (Tyrannosauridae: Albertosaurinae) provide evidence for an ontogenetic dietary shift in tyrannosaurids|journal=Canadian Journal of Earth Sciences|volume=58|issue=9|pages=812–828|doi=10.1139/cjes-2020-0177|bibcode=2021CaJES..58..812T |s2cid=234026715 |url=https://tspace.library.utoronto.ca/bitstream/1807/106568/1/cjes-2020-0177.pdf}}</ref> In 2022, Sakamoto estimated that ''Gorgosaurus'' had an anterior bite force of 6,418 newtons and a posterior bite force of 13,817 newtons.<ref>{{cite journal | doi=10.7717/peerj.13731 | title=Estimating bite force in extinct dinosaurs using phylogenetically predicted physiological cross-sectional areas of jaw adductor muscles | year=2022 | last1=Sakamoto | first1=Manabu | journal=PeerJ | volume=10 | pages=e13731 | pmid=35846881 | pmc=9285543 | doi-access=free }}</ref>

In 2023, a juvenile ''Gorgosaurus'' (TMP 2009.12.14) with its ''[[in situ]]'' stomach contents containing two ''[[Citipes]]'' juveniles about a year old intact was reported from the [[Dinosaur Park Formation]]. This juvenile would have been 5-7 years old at the time of death, measuring about {{convert|4|m|ft}} long and weighing around {{convert|335|kg|lb}}. It is much larger than the two ''Citipes'' juveniles that weigh about {{convert|9|-|12|kg}}, contrary to the assumption that tyrannosaurids fed on prey of their size once they reached {{convert|16|-|32|kg|lb}}, indicating that juvenile tyrannosaurids still consumed much smaller prey after exceeding a certain size threshold. It’s a direct dietary evidence that reinforces the theory of 'ontogenetic dietary shift' for tyrannosaurids, as previously inferred by ecological modeling and anatomical features among different age groups. Only the remains of the hindlimbs and caudal vertebrae of juvenile ''Citipes'' were present in the tyrannosaurid's stomach cavity, suggesting that a juvenile ''Gorgosaurus'' may have had preferential consumption of the muscular hindlimbs.<ref>{{Cite journal|last1=Therrien |first1=F. |last2=Zelenitsky |first2=D. K. |last3=Tanaka |first3=K. |last4=Voris |first4=J. T. |last5=Erickson |first5=G. M. |last6=Currie |first6=P. J. |last7=DeBuhr |first7=C. L. |last8=Kobayashi |first8=Y. |title=Exceptionally preserved stomach contents of a young tyrannosaurid reveal an ontogenetic dietary shift in an iconic extinct predator |year=2023 |journal=Science Advances |volume=9 |issue=49 |pages=eadi0505 |doi=10.1126/sciadv.adi0505 |pmid=38064561 |doi-access=free |bibcode=2023SciA....9I.505T |pmc=10846869 }}</ref><ref name="NYT-20231208">{{cite news |last=Greshko |first=Michael |title=A Tyrannosaur Was Found Fossilized, and So Was Its Last Meal - A 75-million-year-old Gorgosaurus fossil is the first tyrannosaur skeleton ever found with a filled stomach. |url=https://www.nytimes.com/2023/12/08/science/tyrannosaur-last-meal-gorgosaurus.html |date=December 8, 2023 |work=[[The New York Times]] |url-status=live |archiveurl=https://archive.today/20231208191652/https://www.nytimes.com/2023/12/08/science/tyrannosaur-last-meal-gorgosaurus.html |archivedate=December 8, 2023 |accessdate=December 9, 2023 }}</ref> [[Thomas R. Holtz Jr.]], a paleontologist who also previously theorized that tyrannosaurs underwent a big dietary shift with maturation, said that the fossil "looks like it was Thanksgiving," as the juvenile ''Gorgosaurus'' was mostly eating the legs of ''Citipes''.<ref>{{Cite news |last=Johnson |first=Carolyn |date=December 8, 2023 |title=Young tyrannosaur died with a full stomach, remarkable fossil reveals |url=https://www.washingtonpost.com/science/2023/12/08/tyrannosaurus-fossil-stomach-contents/ |access-date=January 6, 2024 |newspaper=Washington Post}}</ref>

=== Life history ===
[[File:Tyrannosauridae growth rates.svg|thumb|left|A graph showing the hypothesized growth curves (body mass versus age) of four tyrannosaurids. ''Gorgosaurus'' is shown in blue.]]
[[Gregory Erickson (paleontologist)|Gregory Erickson]] and colleagues have studied the growth and life history of tyrannosaurids using bone [[histology]], which can determine the age of a specimen when it died. A growth curve can be developed when the ages of various individuals are plotted against their sizes on a graph. Tyrannosaurids grew throughout their lives, but underwent tremendous growth spurts for about four years, after an extended juvenile phase. [[Sexual maturity]] may have ended this rapid growth phase, after which growth slowed down considerably in adult animals. Examining five ''Gorgosaurus'' specimens of various sizes, Erickson calculated a maximum growth rate of about {{convert|50|kg|lb|abbr=on}} per year during the rapid growth phase, slower than in tyrannosaurines like ''Daspletosaurus'' and ''Tyrannosaurus'', but comparable to ''Albertosaurus''.<ref name="ericksonetal2004">{{cite journal |last1=Erickson|first1=Gregory M. |last2=Makovicky|first2=Peter J. |last3=Currie|first3= Philip J. |author3-link=Phil Currie |last4=Norell|first4= Mark A. |last5=Yerby|first5=Scott A. |last6=Brochu|first6= Christopher A. |year=2004 |title=Gigantism and comparative life-history parameters of tyrannosaurid dinosaurs |journal=Nature |volume=430 |pages=772–775 |doi=10.1038/nature02699 |pmid=15306807 |issue=7001|bibcode=2004Natur.430..772E |s2cid=4404887 |url=http://doc.rero.ch/record/15279/files/PAL_E2578.pdf }}{{Erratum|doi=10.1038/nature16487|pmid=26675726|http://retractionwatch.com/2016/03/01/high-profile-critic-slams-nature-letters-about-dinosaur-growth-following-corrections/ ''Retraction Watch''}}</ref>

''Gorgosaurus'' spent as much as half its life in the juvenile phase before ballooning up to near-maximum size in only a few years.<ref name="ericksonetal2004" /> This, along with the complete lack of predators intermediate in size between huge adult tyrannosaurids and other small theropods, suggests that these niches may have been filled by juvenile tyrannosaurids. This pattern is seen in modern [[Komodo dragon]]s, whose hatchlings start off as tree-dwelling [[insectivore]]s and slowly mature into massive [[apex predator]]s capable of taking down large vertebrates.<ref name="holtz2004" /> Other tyrannosaurids, including ''Albertosaurus'', have been found in aggregations that some have suggested to represent mixed-age [[pack hunter|packs]], but there is no evidence of gregarious behavior in ''Gorgosaurus''.<ref name="currieetal2005">{{Cite book|last=Currie |first=Philip J. |author-link=Phil Currie |author2=Trexler, David |author3=Koppelhus, Eva B. |author3-link=Eva Koppelhus |author4=Wicks, Kelly |author5=Murphy, Nate |year=2005 |chapter=An unusual multi-individual tyrannosaurid bonebed in the Two Medicine Formation (Late Cretaceous, Campanian) of Montana (USA) |editor=Carpenter, Kenneth |editor-link=Kenneth Carpenter |title=The Carnivorous Dinosaurs |publisher=Indiana University Press |location=Bloomington |pages=313–324 |isbn=978-0-253-34539-4}}</ref><ref name="tankecurrie1998">{{cite journal|last=Tanke |first=Darren H. |author2=Currie, Philip J. |author2-link=Phil Currie |year=1998 |title=Head-biting behavior in theropod dinosaurs: paleopathological evidence |journal=Gaia |volume=15 |pages=167–184 |url=http://www.mnhn.ul.pt/geologia/gaia/12.pdf |url-status=dead |archive-url=https://web.archive.org/web/20080227134632/http://www.mnhn.ul.pt/geologia/gaia/12.pdf |archive-date=February 27, 2008 }} [not printed until 2000]</ref> 

[[File:Gorgosaurus libratus (TMP 91.36.500).jpg|thumb|Restoration of a sub-adult]] 
The discovery of two exceptionally preserved juvenile skulls from ''Gorgosaurus'' suggests that ''Gorgosaurus'' underwent the morphological shift from gracile juveniles to robust adults at an earlier age than ''Tyrannosaurus'', to which it was compared in a study published by Jared Voris ''et al.,'' suggests that the ontogenetic changes occurred at roughly 5-7 years of age in ''Gorgosaurus''; much earlier than its larger and later relative. However, both tyrannosaur genera underwent these ontogenetic transformations at a similar percent of skull length relative to the large known adult individuals. The study's results likewise indicate that there is a dissociation between body size and cranial development in tyrannosaurs, while simultaneously allowing better identification of juvenile remains that may have been misidentified in museum fossil collections.<ref>{{Cite journal |last1=Voris |first1=Jared T. |last2=Zelenitsky |first2=Darla K. |last3=Therrien |first3=François |last4=Ridgely |first4=Ryan C. |last5=Currie |first5=Philip J. |last6=Witmer |first6=Lawrence M. |date=2021 |title=Two exceptionally preserved juvenile specimens of Gorgosaurus libratus (Tyrannosauridae, Albertosaurinae) provide new insight into the timing of ontogenetic changes in tyrannosaurids |journal=Journal of Vertebrate Paleontology |volume=41 |issue=6 |at=e2041651 |doi=10.1080/02724634.2021.2041651 |bibcode=2021JVPal..41E1651V |s2cid=248197540 |issn=0272-4634}}</ref> It is estimated that an ontogenetic dietary shift of ''Gorgosaurus'' and ''Albertosaurus'' occurs when the mandibular length reaches {{cvt|58|cm|ft}}, indicating that this is the stage when their bite force increases exponentially and when they begin to pursuit large prey.<ref name="TZVT21" />
=== Paleopathology ===
{{Main|Paleopathology}}
[[File:Tyrrell Gorgosaurus.jpg|thumb|Sub-adult specimen TMP91.36.500 in "[[death pose]]", [[Royal Tyrrell Museum of Palaeontology]]]]
Several pathologies have been documented in the ''Gorgosaurus libratus'' [[holotype]], NMC 2120. These include the third right dorsal rib, as well as healed fractures on the 13th and 14th gastralia and left fibula. Its fourth left metatarsal bore roughened [[exostoses]] both in the middle and at the far end. The third phalanx of the third right toe is deformed, as the claw on that digit has been described as "quite small and amorphous". The three pathologies may have been received in a single encounter with another dinosaur.<ref name="rothschild-dino">Rothschild, B., Tanke, D. H., and Ford, T. L., 2001, Theropod stress fractures and tendon avulsions as a clue to activity: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p.&nbsp;331–336.</ref>

{{multiple image
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| header            = TMP 2017.012.0002
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| image1            = Royal Tyrell pathological Gorgosaurus right maxilla..jpg
| image2            = Schematic diagram exhibit of Royal Tyrrell pathological Gorgosaurus right maxilla.jpg
| caption2          = ''Gorgosaurus'' right maxilla with 5 raised scars; healed bite marks.
}}

Another specimen cataloged as [[Royal Tyrrell Museum of Palaeontology|TMP]]94.12.602 bears multiple pathologies. A {{convert|10|cm|in|abbr=on}} [[Anatomical terms of location|longitudinal]] fracture is present in the middle of the right fibula's shaft. Multiple ribs bear healed fractures and the specimen had a [[pseudoarthortic]] [[gastralium]]. Lesions from a bite received to the face were present and showed evidence that the wounds were healing before the animal died.<ref name="rothschild-dino" />

Another specimen has a poorly healed fracture of the right [[fibula]], which left a large [[callus]] on the bone. In a 2001 study conducted by Bruce Rothschild and other paleontologists, 54 foot bones referred to ''Gorgosaurus'' were examined for signs of [[stress fracture]], but none were found.<ref name="rothschild-dino" /><ref name="molnar-pathology">Molnar, R. E., 2001, Theropod paleopathology: a literature survey: In: Mesozoic Vertebrate Life, edited by Tanke, D. H., and Carpenter, K., Indiana University Press, p.&nbsp;337–363.</ref>

As with many tyrannosaurids, several ''Gorgosaurus'' specimens show evidence of [[Intraspecific competition|intraspecific]] face biting.<ref name=":0">{{Cite journal |last1=Brown |first1=Caleb M. |last2=Currie |first2=Philip J. |last3=Therrien |first3=François |date=February 2022 |title=Intraspecific facial bite marks in tyrannosaurids provide insight into sexual maturity and evolution of bird-like intersexual display |url=https://www.cambridge.org/core/journals/paleobiology/article/intraspecific-facial-bite-marks-in-tyrannosaurids-provide-insight-into-sexual-maturity-and-evolution-of-birdlike-intersexual-display/4AC2A6108BC1CE8E849280D9BC4BD9BB |journal=Paleobiology |language=en |volume=48 |issue=1 |pages=12–43 |doi=10.1017/pab.2021.29 |bibcode=2022Pbio...48...12B |issn=0094-8373|url-access=subscription }}</ref>
[[File:Daspletosaurus with bite marks.jpg|alt=TMP 1994.143.1, the skull of a juvenile tyrannosaur from the Dinosaur Park Formation previously thought to be Daspletosaurus sp. but since 2019 assigned to Gorgosaurus libratus. The arrows point at various tyrannosaur bite marks.|thumb|[[Royal Tyrrell Museum of Palaeontology|TMP]] 1994.143.1, the skull of a juvenile tyrannosaur from the [[Dinosaur Park Formation]] previously thought to be ''[[Daspletosaurus]]'' sp. but since 2019 assigned to ''Gorgosaurus libratus''. The arrows point at various tyrannosaur bite marks.]]
Specimen TMP 1994.143.1, a juvenile skull from the [[Dinosaur Park Formation]] with several tyrannosaur bite marks, was previously believed to be ''[[Daspletosaurus]]'' sp.<ref>{{cite journal |last1=Currie |first1=Philip J. |title=Allometric growth in tyrannosaurids (Dinosauria: Theropoda) from the Upper Cretaceous of North America and Asia |journal=Canadian Journal of Earth Sciences |date=April 2003 |volume=40 |issue=4 |pages=651–665 |doi=10.1139/e02-083 |bibcode=2003CaJES..40..651C |url=https://cdnsciencepub.com/doi/10.1139/e02-083}}</ref><ref>{{cite journal |last1=Currie |first1=Philip J. |title=Cranial anatomy of tyrannosaurid dinosaurs from the Late Cretaceous of Alberta, Canada |journal=Acta Palaeontologica Polonica |date=2003 |volume=48 |issue=2 |pages=191–226 |doi=10.7939/R3M90287B |url=https://era.library.ualberta.ca/items/a9200be3-88e3-44f1-9d54-16ce24393533/view/40dc9dcd-6549-49fb-84eb-0537b748e1ff/APP_48_2003_191.pdf}}</ref><ref>{{cite journal |last1=Hone |first1=David W.E. |last2=Tanke |first2=Darren H. |title=Pre- and postmortem tyrannosaurid bite marks on the remains of ''Daspletosaurus'' (Tyrannosaurinae: Theropoda) from Dinosaur Provincial Park, Alberta, Canada |journal=PeerJ |date=April 9, 2015 |volume=3 |pages=e885 |doi=10.7717/peerj.885 |doi-access=free |pmid=25870775 |pmc=4393819 }}</ref> but was later assigned to ''Gorgosaurus libratus''.<ref>{{cite journal |last1=Voris |first1=Jared T. |last2=Zelenitsky |first2=Darla K. |last3=Therrien |first3=François |last4=Currie |first4=Philip J. |title=Reassessment of a juvenile ''Daspletosaurus'' from the Late Cretaceous of Alberta, Canada with implications for the identification of immature tyrannosaurids |journal=Scientific Reports |date=28 November 2019 |volume=9 |issue=17801 |page=17801 |doi=10.1038/s41598-019-53591-7 |pmid=31780682 |pmc=6882908 |bibcode=2019NatSR...917801V }}</ref><ref>{{cite journal |last1=Coppock |first1=Colton C. |last2=Powers |first2=Mark J. |last3=Voris |first3=Jared T. |last4=Sharpe |first4=Henry S. |last5=Currie |first5=Philip J. |title=Immature ''Daspletosaurus'' sp. specimens from the Dinosaur Park Formation provide insight into ontogenetically invariant tyrannosaurid cranial morphology |journal=Canadian Journal of Earth Sciences |date=26 November 2024 |volume=61 |issue=12 |pages=1227–1239 |doi=10.1139/cjes-2024-0083 |url=https://cdnsciencepub.com/doi/10.1139/cjes-2024-0083|url-access=subscription }}</ref>

TMP 2017.012.0002, is a ''Gorgosaurus'' right maxilla with 5 raised scars; healed injuries from face biting by [[conspecifics]]. <ref name=":0" />

TMP91.36.500 is a very complete sub-adult ''Gorgosaurus'' with preserved face bite injuries and also has a thoroughly healed fracture in the right fibula. Also present was a healed fracture in the dentary and what the authors describing the specimen referred to as "a mushroom-like [[hyperostosis]] of a right pedal phalanx." Ralph Molnar has speculated that this may be the same kind of pathology afflicting an unidentified [[ornithomimid]] discovered with a similar mushroom shaped growth on a toe bone.<ref name="rothschild-dino" /> TMP91.36.500 is also preserved in a characteristic [[death pose]].<ref name="reisdorf2012">{{cite journal | last1 = Reisdorf | first1 = A.G. | last2 = Wuttke | first2 = M. | year = 2012 | title = Re-evaluating Moodie's Opisthotonic-Posture Hypothesis in fossil vertebrates. Part I: Reptiles&nbsp;– The taphonomy of the bipedal dinosaurs ''Compsognathus longipes'' and ''Juravenator starki'' from the Solnhofen Archipelago (Jurassic, Germany) | journal = Palaeobiodiversity and Palaeoenvironments | volume =  92| issue = 1 | pages =  119–168| doi = 10.1007/s12549-011-0068-y | bibcode = 2012PdPe...92..119R | s2cid = 129785393 }}</ref>