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{{short description|Spike arrangement on stegosaur tails}}
{{Use mdy dates|date=May 2019}}
[[File:Thagomizer 01.jpg|thumb|Thagomizer on a mounted ''[[Stegosaurus]]'' tail]]
A '''thagomizer''' ({{IPAc-en|ˈ|θ|æ|ɡ|ə|m|aɪ|z|ər}}) is the distinctive arrangement of spike-shaped [[Osteoderm|osteoderms]] on the tails of some [[Stegosauria|stegosaurian]] dinosaurs. These spikes are believed to have been a defensive measure against predators.

The arrangement of spikes originally had no distinct name. Cartoonist [[Gary Larson]] invented the name "thagomizer" in 1982 as a joke in his comic strip ''[[The Far Side]]'', and it was gradually adopted as an informal term sometimes used within scientific circles, research, and education.

==Etymology==
[[File:Thagomizer.png|thumb|250px|right|alt=A cartoon of a group of cavemen. One points at a diagram of a dinosaur's tail with four spikes. The caption reads, "Now, this end is called the thagomizer...after the late Thag Simmons."|This ''[[The Far Side|Far Side]]'' cartoon is the source of the term ''thagomizer''.]]
The term ''thagomizer'' was coined by [[Gary Larson]] in jest. In a 1982 ''[[The Far Side]]'' [[comic]], a group of [[caveman|cavemen]] are taught by a caveman lecturer that the spikes on a stegosaur's tail were named "after the late Thag Simmons".<ref>{{Cite web|url=https://www.smithsonianmag.com/science-nature/watch-out-for-that-thagomizer-98891562/|title=Watch Out For That Thagomizer! |last=Black|first=Riley|date=March 30, 2011|website=Smithsonian.com|access-date=May 28, 2019}}</ref>

The term was picked up initially by [[Kenneth Carpenter]], then a paleontologist at the [[Denver Museum of Nature and Science]], who used the term when describing a fossil at the [[Society of Vertebrate Paleontology]] Annual Meeting in 1993.<ref name="nsci">{{cite web|url=https://www.newscientist.com/channel/life/mg19125592.200-the-word-thagomizer.html|title= The word: Thagomizer|archive-url=https://web.archive.org/web/20070930013238/http://www.newscientist.com/channel/life/mg19125592.200-the-word-thagomizer.html |archive-date=September 30, 2007 |website=[[New Scientist]]|date=July 8, 2006|url-access=subscription }}</ref> ''Thagomizer'' has since been adopted as an informal [[anatomical]] term<ref name="TRHJ07">{{cite book |last=Holtz |first=Thomas, R. Jr. |author-link=Thomas R. Holtz Jr. |year=2007 |title=Dinosaurs: the Most Complete, Up-To-Date Encyclopedia for Dinosaur Lovers of All Ages |publisher=Random House |location=New York |isbn=978-0-375-82419-7 |page=[https://archive.org/details/dinosaursmostcom00holt/page/230 230] |url-access=registration |url=https://archive.org/details/dinosaursmostcom00holt/page/230 }}</ref> and is used by the [[Smithsonian Institution]],<ref name="nsci" /><ref>{{cite web |url=http://www.nmnh.si.edu/paleo/dino/stegdcvr.htm |url-status=dead |archive-url=https://web.archive.org/web/20041214142258/http://www.nmnh.si.edu/paleo/dino/stegdcvr.htm |archive-date=December 14, 2004 |title=Stegosaurus Changes |publisher=Smithsonian National Museum of Natural History, Department of Paleobiology |access-date=March 3, 2007}}</ref> the [[Dinosaur National Monument]],<ref name="nsci"/> the book ''The Complete Dinosaur''<ref name="TCD">{{cite encyclopedia|first1=Peter M. |last1=Galton|author-link1=Peter Galton|editor1-last=Farlow|editor1-first=James Orville|editor2-last=Brett-Surman|editor2-first=M. K.|encyclopedia=The Complete Dinosaur|title=Stegosaurs|date=1999|publisher=Indiana University Press|pages=302|url=https://books.google.com/books?id=FOViD-lDPy0C&pg=302|access-date=December 11, 2016 |quote=In all stegosaurs, the terminal tail spines (thagomizer) presumably played a role in defense. |isbn=978-0253213136}}</ref> and the BBC documentary series ''[[Planet Dinosaur]]''.<ref>{{Cite episode |title=Fight For Life |url=https://vimeo.com/131296159#t=9m14s |access-date=December 11, 2016 |series=Planet Dinosaur |network=BBC |station=BBC One |date=November 26, 2015 |season=1 |number=4  |time=9 minutes 14 seconds |quote=Stegosaurus: a heavily armored tank with a deadly weapon at the end of its tail, known as a thagomizer. |language=en}}</ref> The term has also appeared in some technical papers describing stegosaurs and related dinosaurs.<ref>{{Cite journal|last1=Mallison|first1=Heinrich|year=2011|title=Defense capabilities of ''Kentrosaurus aethiopicus'' Hennig, 1915|journal=Palaeontologia Electronica|volume=14|issue=2|pages=10A|url=https://www.uv.es/pe/2011_2/255/255.pdf}}</ref><ref>{{Cite journal| doi = 10.1371/journal.pone.0224263| issn = 1932-6203| volume = 14| issue = 11| pages = –0224263| last1 = Costa| first1 = Francisco| last2 = Mateus| first2 = Octávio| title = Dacentrurine stegosaurs (Dinosauria): A new specimen of Miragaia longicollum from the Late Jurassic of Portugal resolves taxonomical validity and shows the occurrence of the clade in North America| journal = PLOS ONE| date = 2019-11-13| pmid = 31721771| pmc = 6853308| bibcode = 2019PLoSO..1424263C| doi-access = free}}</ref><ref>{{Cite journal| doi = 10.1038/s41586-021-04147-1| last1 = Soto-Acuña| first1 = Sergio| last2 = Vargas| first2 = Alexander| last3 = Kaluza| first3 = Jonatan| last4 = Leppe| first4 = Marcelo| last5 = Botelho| first5 = Joao| last6 = Palma-Liberona| first6 = José| last7 = Gutstein| first7 = Carolina| last8 = Fernández| first8 = Roy| last9 = Ortiz| first9 = Hector| last10 = Milla| first10 = Verónica| last11 = Aravena| first11 = Bárbara| last12 = Manríquez| first12 = Leslie| last13 = Alarcón-Muñoz| first13 = Jhonatan| last14 = Pino| first14 = Juan| last15 = Trevisan| first15 = Christine| last16 = Mansilla| first16 = Héctor| last17 = Hinojosa| first17 = Luis| last18 = Muñoz-Walther| first18 = Vicente| last19 = Rubilar-Rogers| first19 = David| title = Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile| journal = Nature| date = 2021-12-01| volume = 600| issue = 7888| pages = 259–263| pmid = 34853468| bibcode = 2021Natur.600..259S| s2cid = 244799975}}</ref><ref>{{Cite journal|doi=10.1007/s12542-022-00605-x |title=New thyreophoran dinosaur material from the Early Jurassic of northeastern Germany |date=2022 |last1=Schade |first1=Marco |last2=Ansorge |first2=Jörg |journal=PalZ |volume=96 |issue=2 |pages=303–311 |bibcode=2022PalZ...96..303S |doi-access=free }}</ref><ref>{{cite journal |last1=Lategano |first1=Francesco |last2=Conti |first2=Simone |last3=Lozar |first3=Francesca |year=2024 |title=''Miragaia'' tail biomechanics and defences. Evaluation of the tail mobility and resistance to loadings and collisions |journal=Rivista Italiana di Paleontologia e Stratigrafia |volume=130 |issue=2 |pages=475-486 |doi=10.54103/2039-4942/21688 |url=https://iris.unito.it/bitstream/2318/2034711/1/Lategano_et_al2024.pdf}}</ref>

== Paleobiology ==
[[File:Kentrosaurus aethiopicus 01.jpg|thumb|left|Skeleton of ''[[Kentrosaurus]]'']]
Some stegosaurs such as ''[[Kentrosaurus]]'' do not have a distinct "thagomizer" comprised of two pairs of spikes, as in these species there is not clear differentiation between the last two pairs on the tail and the other tail [[Osteoderm|osteoderms]], which are also spike-like, unlike the broad plate-like osteoderms on the back of ''Stegosaurus''.<ref>{{Citation |last=Saitta |first=Evan T. |title=The function and Evolution of Stegosaur Osteoderms and Hypothesized Sexual Dimorphism in Hesperosaurus |date=2025-04-16 |url=http://biorxiv.org/lookup/doi/10.1101/2025.04.10.648273 |access-date=2025-05-28 |language=en |doi=10.1101/2025.04.10.648273 |last2=Bonhomme |first2=Vincent |last3=Lukens |first3=Mitchell |last4=Vidal |first4=Daniel |last5=Longrich |first5=Nicholas R. |last6=Richmond |first6=Dean R. |last7=Stockdale |first7=Maximilian T.|doi-access=free }}</ref>

There has been debate about whether the thagomizer was used simply for display, as posited by [[Charles W. Gilmore|Gilmore]] in 1914,<ref name="gilmore14">{{cite journal|author=Gilmore, C. W.|year=1914|title=Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus ''Stegosaurus''|url=https://archive.org/details/osteologyofarmor00gilm|journal=Series: Smithsonian Institution. United States National Museum. Bulletin 89|publisher=Government Printing Office, Washington|issue=89}}</ref> or used as a defensive weapon. [[Robert T. Bakker|Robert Bakker]] noted that it is likely that the stegosaur tail was much more flexible than those of other [[ornithischia]]n dinosaurs because it lacked ossified tendons, thus lending credence to the idea of the thagomizer being a weapon. He also observed that ''[[Stegosaurus]]'' could have maneuvered its rear easily by keeping its large hindlimbs stationary and pushing off with its very powerfully muscled but short forelimbs, allowing it to swivel deftly to deal with attack.<ref name="bakker86">{{cite book|author=Bakker, R. T.|url=https://archive.org/details/dinosaurheresies0000bakk|title=The Dinosaur Heresies|publisher=William Morrow|year=1986|location=New York| isbn=9780688042875 |url-access=registration}}{{ISBN?}}{{page needed|date=June 2020}}</ref> In 2010, analysis of a digitized model of ''[[Kentrosaurus|Kentrosaurus aethiopicus]]'' showed that the tail could bring the thagomizer around to the sides of the dinosaur, possibly striking an attacker beside it.<ref name="NaishDK">{{cite web|author=Naish, Darren|year=2010|title=Heinrich's digital Kentrosaurus: the SJG stegosaur special, part II|url=http://scienceblogs.com/tetrapodzoology/2011/01/heinrichs_digital_kentrosaurus.php|url-status=dead|archive-url=https://web.archive.org/web/20110109004732/http://scienceblogs.com/tetrapodzoology/2011/01/heinrichs_digital_kentrosaurus.php|archive-date=January 9, 2011|access-date=January 19, 2011|work=Tetrapod Zoology}}</ref>

[[File:Thagomizer.tif|thumb|''Allosaurus'' tail [[vertebra]] with a hole matching a thagomizer spine]]
In 2001, a study of thagomizers by McWhinney et al.<ref>{{cite book|last1=McWhinney |first1=L. A. |last2=Rothschild |first2=B. M. |last3=Carpenter |first3=K.|title=The Armored Dinosaurs|publisher=Indiana University Press|year=2001|isbn=978-0-253-33964-5|editor=Carpenter, Kenneth|pages=141–56|chapter=Posttraumatic Chronic [[Osteomyelitis]] in ''Stegosaurus'' dermal spikes}}</ref> showed a high incidence of trauma-related damage. This too supports the theory that the principal function of the thagomizer was defense in combat. There is also evidence for a defense function in the form of an ''[[Allosaurus]]'' tail vertebra with a partially healed puncture wound that fits a ''Stegosaurus'' tail spike.<ref name="CSMW2005">{{cite book|last=Carpenter|first=Kenneth|url=https://archive.org/details/carnivorousdinos00carp|title=The Carnivorous Dinosaurs|author2=Sanders, Frank|author3=McWhinney, Lorrie A.|author4=Wood, Lowell|publisher=[[Indiana University Press]]|year=2005|isbn=978-0-253-34539-4|editor=Carpenter, Kenneth|location=Bloomington and Indianapolis|page=[https://archive.org/details/carnivorousdinos00carp/page/n330 325]|chapter=Evidence for predator-prey relationships: Examples for ''Allosaurus'' and ''Stegosaurus''|url-access=limited|name-list-style=amp}}</ref> This usage of the thagomizer would be similar to defensive behaviors in some extant lizards with tail spikes, such as the [[giant girdled lizard]].<ref>{{cite journal |last1=Ebel |first1=R. |last2=Herrel |first2=A. |last3=Scheyer |first3=T. M. |last4=Keogh |first4=J. S. |date=January 2025 |title=Review of osteoderm function and future research directions |journal=Journal of Zoology |volume=325 |issue=1 |pages=1-24 |doi=10.1111/jzo.13224 |url=https://zslpublications.onlinelibrary.wiley.com/doi/10.1111/jzo.13224 |doi-access=free|url-access=subscription }}</ref>

The species of stegosaur known as ''Stegosaurus stenops'' had four dermal spikes, each about {{cvt|60|-|90|cm|ft|0}} long. Discoveries of articulated stegosaur armor show that, at least in some species, these spikes protruded horizontally from the tail, not vertically as is often depicted.<ref name=Carpenter98>{{cite journal |last=Carpenter |first=Kenneth |year=1998 |journal=Modern Geology |title=Armor of ''Stegosaurus stenops'', and the taphonomic history of a new specimen from Garden Park, Colorado |volume=23 |pages=127–44}}</ref> Initially, [[Othniel Charles Marsh]] described ''S. armatus'' as having eight spikes in its tail, unlike ''S. stenops''. However, recent research re-examined this and concluded this species also had four.<ref name="Marsh77">{{cite journal|last1=Marsh|first1=O. C|year=1877|title=A new order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains|url=https://zenodo.org/record/1450038|journal=American Journal of Science|volume=14|issue=84|pages=513–14|bibcode=1877AmJS...14..513M|doi=10.2475/ajs.s3-14.84.513|s2cid=130078453}}</ref><ref name="8spike">{{cite book|last1=Carpenter |first1=K. |last2=Galton |first2=P. M.|title=The Armored Dinosaurs|publisher=Indiana University Press|year=2001|isbn=978-0-253-33964-5|editor=Carpenter, Kenneth|pages=76–102|chapter=Othniel Charles Marsh and the Eight-Spiked ''Stegosaurus''}}</ref>

== Other uses ==
=== Mathematics ===
[[File:Thagomizer-graph.svg|thumb|The thagomizer graph {{math|''K''<sub>1,1,''n''</sub>}} is [[Multipartite graph|tripartite]]]]
In a 2017 paper, the term [[thagomizer graph]] (and also the associated "thagomizer [[matroid]]") was introduced for the [[Multipartite graph|complete tripartite graph]] {{math|''K''<sub>1,1,''n''</sub>}}.<ref>{{cite journal|last1=Gedeon|first1=Katie|last2=Proudfoot|first2=Nicholas|last3=Young|first3=Benjamin|date=2017|title=Kazhdan-Lusztig polynomials of matroids: a survey of results and conjectures|url=https://www.emis.de/journals/SLC/wpapers/FPSAC2017/80%20Gedeon%20Proudfoot%20Young.pdf|journal=Séminaire Lotharingien de Combinatoire|volume=78B|page=80|arxiv=1611.07474}}</ref>

=== Molecular biology ===
In 2023, researchers at the University of California, San Francisco presented ''Thagomizer'', a modality for the interrogation of RNA-protein binding events in [[Cross-linking immunoprecipitation|CLIP-Seq]] (Cross-linking and immunoprecipitation) data.<ref>{{Cite journal |last1=Zhu |first1=Wandi S. |last2=Litterman |first2=Adam J. |last3=Sekhon |first3=Harshaan S. |last4=Kageyama |first4=Robin |last5=Arce |first5=Maya M. |last6=Taylor |first6=Kimberly E. |last7=Zhao |first7=Wenxue |last8=Criswell |first8=Lindsey A. |last9=Zaitlen |first9=Noah |last10=Erle |first10=David J. |last11=Ansel |first11=K. Mark |date=2023-12-07 |title=GCLiPP: global crosslinking and protein purification method for constructing high-resolution occupancy maps for RNA binding proteins |journal=Genome Biology |volume=24 |issue=1 |pages=281 |doi=10.1186/s13059-023-03125-2 |doi-access=free |issn=1474-760X |pmc=10701951 |pmid=38062486}}</ref><ref>{{Cite web |title=Thagomizer |url=https://thagomizer.ucsf.edu/ |access-date=2024-01-12 |website=thagomizer.ucsf.edu}}</ref>

==See also==
{{Portal|Dinosaurs}}
*[[Tail club]]
*[[Timeline of stegosaur research]]

==References==
{{reflist}}

{{Thefarside}}

[[Category:Dinosaur anatomy]]
[[Category:The Far Side]]
[[Category:Stegosauria]]
[[Category:1980s neologisms]]
[[Category:Words originating in fiction]]