Editing Gorgosaurus (section)

== Discovery and naming ==
[[File:Sharp naturalhistory1920 deinodon.jpg|thumb|left|[[Type specimen]] of ''Gorgosaurus sternbergi'' ([[American Museum of Natural History|AMNH]] 5664), now recognized as a juvenile ''Gorgosaurus libratus'']]
''Gorgosaurus libratus'' was first described by [[Lawrence Lambe]] in 1914.<ref name=lambe1914a>{{cite journal |last=Lambe |first=Lawrence M. |author-link=Lawrence Lambe |year=1914 |title=On the fore-limb of a carnivorous dinosaur from the Belly River Formation of Alberta, and a new genus of Ceratopsia from the same horizon, with remarks on the integument of some Cretaceous herbivorous dinosaurs |journal=Ottawa Naturalist |volume=27 |pages=129–135}}</ref><ref name=lambe1914b>{{cite journal |last=Lambe |first=Lawrence M. |author-link=Lawrence Lambe |year=1914 |title=On a new genus and species of carnivorous dinosaur from the Belly River Formation of Alberta, with a description of ''Stephanosaurus marginatus'' from the same horizon |journal=Ottawa Naturalist |volume=28 |pages=13–20 |url=https://www.biodiversitylibrary.org/page/5739477#page/19/mode/1up}}</ref> Its name is derived from the [[Ancient Greek|Greek]] {{lang|grc|{{math|γοργος}}}} (''gorgos'' – "fierce" or "terrible") and {{lang|grc|{{math|σαυρος}}}} (''saurus'' – "lizard").<ref name=liddellscott>{{cite book |author1=Liddell, Henry G. |author-link=Henry Liddell |author2=Scott, Robert |author-link2=Robert Scott (philologist) |year=1980 |title=Greek-English Lexicon |edition=abridged |publisher=Oxford University Press |location=Oxford, UK |isbn=978-0-19-910207-5 |url=https://archive.org/details/lexicon00lidd }}</ref> The [[type species]] is ''G.&nbsp;libratus''; the specific epithet "balanced" is the [[past participle]] of the [[Latin]] verb ''librare'', meaning "to balance".<ref name=lambe1914b/>

The [[holotype]] of ''Gorgosaurus libratus'' ([[Canadian Museum of Nature|NMC]] 2120) is a nearly complete skeleton associated with a skull, discovered in 1913 by [[Charles M. Sternberg]]. This specimen was the first tyrannosaurid found with a complete hand.<ref name=lambe1914a/> It was found in the [[Dinosaur Park Formation]] of Alberta and is housed in the [[Canadian Museum of Nature]] in [[Ottawa]].<ref name=currie2003a/> Prospectors from the [[American Museum of Natural History]] in [[New York City]] were active along the [[Red Deer River]] in Alberta at the same time, collecting hundreds of spectacular dinosaur specimens, including four complete ''G.&nbsp;libratus'' skulls, three of which were associated with skeletons. Matthew and Brown described four of these specimens in 1923.<ref name=matthewbrown1923/>

[[File:Gorgosaurus.jpg|thumb|Specimen [[American Museum of Natural History|AMNH]]&nbsp;5458]]
Matthew and Brown also described a fifth skeleton ([[American Museum of Natural History|AMNH]]&nbsp;5664), which [[Charles H. Sternberg]] had collected in 1917 and sold to their museum. It was smaller than other ''Gorgosaurus'' specimens, with a lower, lighter skull and more elongate limb proportions. Many [[Suture (anatomical)|sutures]] between bones were unfused in this specimen as well. Matthew and Brown noted that these features were characteristic of juvenile tyrannosaurids, but still described it as the holotype of a new species, ''G.&nbsp;sternbergi''.<ref name=matthewbrown1923/> Today's paleontologists regard this specimen as a juvenile ''G.&nbsp;libratus''.<ref name=holtz2004/><ref name=currie2003a/> Dozens of other specimens have been excavated from the Dinosaur Park Formation and are housed in museums across the United States and Canada.<ref name=russell1970/><ref name=currie2003a/> ''G.&nbsp;libratus'' is the best-represented tyrannosaurid in the fossil record, known from a virtually complete growth series.<ref name=holtz2004/><ref name=carr1999>{{cite journal |doi=10.1080/02724634.1999.10011161 |last=Carr |first=Thomas D. |author-link=Thomas Carr (paleontologist) |year=1999 |title=Craniofacial ontogeny in Tyrannosauridae (Dinosauria, Coelurosauria) |journal=Journal of Vertebrate Paleontology |volume=19 |issue=3 |pages=497–520 |bibcode=1999JVPal..19..497C |s2cid=83744433 |url=http://www.vertpaleo.org/publications/jvp/19-497-520.cfm |access-date=February 27, 2008 |archive-date=September 30, 2008 |archive-url=https://web.archive.org/web/20080930215300/http://www.vertpaleo.org/publications/jvp/19-497-520.cfm |url-status=dead |url-access=subscription }}</ref>

[[File:Gorgosaurus skeleton AMNH 5428.jpg|thumb|left|Specimen [[National Museum of Natural History|USNM]]&nbsp;12814 (formerly [[American Museum of Natural History|AMNH]]&nbsp;5428)]]
In 1856, [[Joseph Leidy]] described two tyrannosaurid premaxillary teeth from Montana. Although there was no indication of what the animal looked like, the teeth were large and robust, and Leidy gave them the name ''[[Deinodon]]''.<ref name=leidy1856>{{cite journal |last=Leidy |first=Joseph |author-link=Joseph Leidy |year=1856 |title=Notice of remains of extinct reptiles and fishes, discovered by Dr. F.V. Hayden in the badlands of the Judith River |journal=Proceedings of the Academy of Sciences in Philadelphia |volume=8 |pages=72–73}}</ref> Matthew and Brown commented in 1922 that these teeth were indistinguishable from those of ''Gorgosaurus'', but in the absence of skeletal remains of ''Deinodon'', opted not to unequivocally synonymize the two genera, provisionally naming a ''?Deinodon libratus''.<ref name=matthewbrown1922/> Although ''Deinodon'' teeth are very similar to those of ''Gorgosaurus'', tyrannosaurid teeth are extremely uniform, so it cannot be said for certain which animal they belonged to. ''Deinodon'' is usually regarded as a ''[[nomen dubium]]'' today.<ref name=carr1999/> Additional likely synonyms of ''G.&nbsp;libratus'' and/or ''D.&nbsp;horridus'' include ''[[Laelaps falculus]]'', ''[[Laelaps hazenianus]]'', ''Laelaps incrassatus'', and ''[[Dryptosaurus kenabekides]]''.<ref name=dinosauria2>{{cite book |editor1=Weishampel, D.B. |editor2=Dodson, P. |editor3=Osmólska, H. |year=2004 |title=The Dinosauria |edition=2nd |publisher=University of California Press |place=Berkeley, CA}}</ref>

Several tyrannosaurid skeletons from the [[Two Medicine Formation]] and [[Judith River Formation]] of [[Montana]] probably belong to ''Gorgosaurus'', although it remains uncertain whether they belong to ''G.&nbsp;libratus'' or a new species.<ref name=currie2003a/> One specimen from Montana ([[Children's Museum of Indianapolis|TCMI]] 2001.89.1), housed in the [[Children's Museum of Indianapolis]], shows evidence of severe [[pathology|pathologies]], including healed leg, rib, and vertebral [[Bone fracture|fractures]], [[osteomyelitis]] (infection) at the tip of the lower jaw resulting in permanent tooth loss, and possibly a [[brain tumor]].<ref name=natlgeo2003>{{Cite web |author=Pickrell, John |date=November 24, 2003 |url=http://news.nationalgeographic.com/news/2003/11/1124_031124_dinocancer.html |archive-url=https://web.archive.org/web/20031126034023/http://news.nationalgeographic.com/news/2003/11/1124_031124_dinocancer.html |url-status=dead |archive-date=November 26, 2003 |title=First dinosaur brain tumor found, experts suggest |publisher=National Geographic News |access-date=February 7, 2008}}</ref><ref name=tcmigorgo>{{Cite web |url=http://www.childrensmuseum.org/themuseum/dinosphere/profiles/gorgo.html |title=Meet the Gorgosaur |publisher=The Children's Museum of Indianapolis |access-date=February 7, 2008 |url-status=dead |archive-url=https://web.archive.org/web/20080130171049/http://www.childrensmuseum.org/themuseum/dinosphere/profiles/gorgo.html |archive-date=January 30, 2008 }}</ref>

=== Formerly assigned species ===
[[File:TarbosaurusP1050352.jpg|thumb|Cast of specimen PIN 553–1, holotype of now invalid ''Gorgosaurus lancinator'']]
Several species were incorrectly assigned to ''Gorgosaurus'' in the 20th century. A complete skull of a small tyrannosaurid ([[Cleveland Museum of Natural History|CMNH]] 7541), found in the younger, late [[Maastrichtian]]-age [[Hell Creek Formation]] of Montana, was named ''Gorgosaurus lancensis'' by [[Charles Whitney Gilmore]] in 1946.<ref name=gilmore1946>{{cite journal |last=Gilmore |first=Charles W. |author-link=Charles Whitney Gilmore |year=1946 |title=A new carnivorous dinosaur from the Lance Formation of Montana |journal=Smithsonian Miscellaneous Collections |volume=106 |pages=1–19}}</ref> This specimen was renamed ''[[Nanotyrannus]]'' by [[Robert T. Bakker|Bob Bakker]] and colleagues in 1988.<ref name=bakkeretal1988>{{cite journal |last=Bakker |first=Robert T. |author-link=Robert T. Bakker |author2=Williams, Michael |author3=Currie, Philip J. |author3-link=Phil Currie |year=1988 |title=''Nanotyrannus'', a new genus of pygmy tyrannosaur, from the latest Cretaceous of Montana |journal=Hunteria |volume=1 |issue=5 |pages=1–30}}</ref> Currently, many paleontologists regard ''Nanotyrannus'' as a juvenile ''Tyrannosaurus rex''.<ref name=holtz2004/><ref name=carr1999/> Similarly, [[Evgeny Maleev]] created the names ''Gorgosaurus lancinator'' and ''Gorgosaurus novojilovi'' for two small tyrannosaurid specimens ([[Paleontological Institute of Russian Academy of Sciences|PIN]] 553-1 and PIN 552–2) from the [[Nemegt Formation]] of [[Mongolia]] in 1955.<ref name=maleev1955b>{{cite journal |last=Maleev |first=Evgeny A. |author-link=Evgeny Maleev |year=1955 |title=New carnivorous dinosaurs from the Upper Cretaceous of Mongolia |journal=[[Doklady Akademii Nauk SSSR]] |volume=104 |issue=5 |pages=779–783 |language=ru}}</ref> [[Kenneth Carpenter]] renamed the smaller specimen ''[[Maleevosaurus]] novojilovi'' in 1992,<ref name=carpenter1992>{{Cite book|last=Carpenter |first=Ken. |author-link=Kenneth Carpenter |year=1992 |chapter=Tyrannosaurids (Dinosauria) of Asia and North America |editor=Mateer, Niall J. |editor2=Chen Peiji|title=Aspects of Nonmarine Cretaceous Geology |location=Beijing |publisher=China Ocean Press |pages=250–268 }}</ref> but both are now considered juveniles of ''[[Tarbosaurus bataar]]''.<ref name=holtz2004/><ref name=carr1999/><ref name=rozhdestvensky1965>{{cite journal |last=Rozhdestvensky |first=Anatoly K. |author-link=Anatoly Konstantinovich Rozhdestvensky |year=1965 |title=Growth changes in Asian dinosaurs and some problems of their taxonomy |journal=Paleontological Journal |volume=3 |pages=95–109}}</ref>