A thagomizer (/ˈθæɡəmzər/) is the distinctive arrangement of four spikes on the tails of stegosaurian dinosaurs. These spikes are believed to have been a defensive measure against predators.[2][1]

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 Far Side cartoon is the source of the term thagomizer.
Best evidence for the use of the thagomizer is this Allosaurus tail (caudal) vertebra showing a punctured process. The hole perfectly matches a thagomizer spike.[1]

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.

A thagomizer on the tail of a Stegosaurus fossil



The term thagomizer was coined by Gary Larson in jest. In a 1982 The Far Side comic, a group of cavemen are taught by a caveman lecturer that the spikes on a stegosaur's tail were named "after the late Thag Simmons".[3]

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.[4] Thagomizer has since been adopted as an informal anatomical term[5] and is used by the Smithsonian Institution,[4][6] the Dinosaur National Monument, the book The Complete Dinosaur[7] and the BBC documentary series Planet Dinosaur.[8] The term has also appeared in some technical papers describing stegosaurs and related dinosaurs.[9][10][11][12]

Thagomizer on mounted Stegosaurus tail



There has been debate about whether the thagomizer was used simply for display, as posited by Gilmore in 1914,[13] or used as a defensive weapon. Robert Bakker noted that it is likely that the stegosaur tail was much more flexible than those of other ornithischian 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.[14] In 2010, analysis of a digitized model of Kentrosaurus aethiopicus showed that the tail could bring the thagomizer around to the sides of the dinosaur, possibly striking an attacker beside it.[15]

In 2001, a study of thagomizers by McWhinney et al.[16] 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 Stegosaurus defending itself, in the form of an Allosaurus tail vertebra with a partially healed puncture wound that fits a Stegosaurus tail spike.[17] The species of stegosaur known as Stegosaurus stenops had four dermal spikes, each about 60–90 cm (2–3 ft) 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.[18] Initially, 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.[19][20]


The thagomizer graph K1,1,n is tripartite

In a 2017 paper, the term thagomizer graph (and also the associated "thagomizer matroid") was introduced for the complete tripartite graph K1,1,n.[21]

Molecular biology

A view of the Thagomizer graphing dashboard's graphical user interface (GUI).

In 2023, researchers at the University of California, San Francisco presented Thagomizer, a modality for the interrogation of RNA-protein binding events in CLIP-Seq (Cross-linking and immunoprecipitation) data.[22][23]

See also


Other scientific terms first used in fiction:


  1. ^ a b Carpenter, K., Sanders, F., McWhinney, L., and Wood, L. 2005. Evidence for predator-prey relationships: Example for Allosaurus and Stegosaurus. Pp. 325-350 in Carpenter, K. (ed.) The Carnivorous Dinosaurs. Indiana University Press, Bloomington.
  2. ^ Holtz, T. R., (2000) "Classification and Evolution of the Dinosaur Groups" (pp. 140–168) in The Scientific American Book of Dinosaurs, edited by Gregory S. Paul, New York: St Martin's Press ISBN 0-312-26226-4.
  3. ^ Black, Riley (March 30, 2011). "Watch Out For That Thagomizer!". Smithsonian.com. Retrieved May 28, 2019.
  4. ^ a b "The word: Thagomizer". New Scientist. July 8, 2006. Archived from the original on September 30, 2007.
  5. ^ Holtz, Thomas, R. Jr. (2007). Dinosaurs: the Most Complete, Up-To-Date Encyclopedia for Dinosaur Lovers of All Ages. New York: Random House. p. 230. ISBN 978-0-375-82419-7.{{cite book}}: CS1 maint: multiple names: authors list (link)
  6. ^ "Stegosaurus Changes". Smithsonian National Museum of Natural History, Department of Paleobiology. Archived from the original on December 14, 2004. Retrieved March 3, 2007.
  7. ^ Galton, Peter M. (1999). "Stegosaurs". In Farlow, James Orville; Brett-Surman, M. K. (eds.). The Complete Dinosaur. Indiana University Press. p. 302. ISBN 978-0253213136. Retrieved December 11, 2016. In all stegosaurs, the terminal tail spines (thagomizer) presumably played a role in defense.
  8. ^ "Fight For Life". Planet Dinosaur. Season 1. Episode 4. November 26, 2015. Event occurs at 9 minutes 14 seconds. BBC. BBC One. Retrieved December 11, 2016. Stegosaurus: a heavily armored tank with a deadly weapon at the end of its tail, known as a thagomizer.
  9. ^ Mallison, Heinrich (2011). "Defense capabilities of Kentrosaurus aethiopicus Hennig, 1915" (PDF). Palaeontologia Electronica. 14 (2): 10A.
  10. ^ Costa, Francisco; Mateus, Octávio (November 13, 2019). "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". PLOS ONE. 14 (11): –0224263. Bibcode:2019PLoSO..1424263C. doi:10.1371/journal.pone.0224263. ISSN 1932-6203. PMC 6853308. PMID 31721771.
  11. ^ Soto-Acuña, Sergio; Vargas, Alexander; Kaluza, Jonatan; Leppe, Marcelo; Botelho, Joao; Palma-Liberona, José; Gutstein, Carolina; Fernández, Roy; Ortiz, Hector; Milla, Verónica; Aravena, Bárbara; Manríquez, Leslie; Alarcón-Muñoz, Jhonatan; Pino, Juan; Trevisan, Christine; Mansilla, Héctor; Hinojosa, Luis; Muñoz-Walther, Vicente; Rubilar-Rogers, David (December 1, 2021). "Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile". Nature. 600 (7888): 259–263. Bibcode:2021Natur.600..259S. doi:10.1038/s41586-021-04147-1. PMID 34853468. S2CID 244799975.
  12. ^ Schade, Marco; Ansorge, Jörg (2022). "New thyreophoran dinosaur material from the Early Jurassic of northeastern Germany". PalZ. 96 (2): 303–311. Bibcode:2022PalZ...96..303S. doi:10.1007/s12542-022-00605-x.
  13. ^ Gilmore, C. W. (1914). "Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus Stegosaurus". Series: Smithsonian Institution. United States National Museum. Bulletin 89 (89). Government Printing Office, Washington.
  14. ^ Bakker, R. T. (1986). The Dinosaur Heresies. New York: William Morrow. ISBN 9780688042875.[ISBN missing][page needed]
  15. ^ Naish, Darren (2010). "Heinrich's digital Kentrosaurus: the SJG stegosaur special, part II". Tetrapod Zoology. Archived from the original on January 9, 2011. Retrieved January 19, 2011.
  16. ^ McWhinney, L. A.; Rothschild, B. M.; Carpenter, K. (2001). "Posttraumatic Chronic Osteomyelitis in Stegosaurus dermal spikes". In Carpenter, Kenneth (ed.). The Armored Dinosaurs. Indiana University Press. pp. 141–56. ISBN 978-0-253-33964-5.
  17. ^ Carpenter, Kenneth; Sanders, Frank; McWhinney, Lorrie A. & Wood, Lowell (2005). "Evidence for predator-prey relationships: Examples for Allosaurus and Stegosaurus". In Carpenter, Kenneth (ed.). The Carnivorous Dinosaurs. Bloomington and Indianapolis: Indiana University Press. p. 325. ISBN 978-0-253-34539-4.
  18. ^ Carpenter, Kenneth (1998). "Armor of Stegosaurus stenops, and the taphonomic history of a new specimen from Garden Park, Colorado". Modern Geology. 23: 127–44.
  19. ^ Marsh, O. C (1877). "A new order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains". American Journal of Science. 14 (84): 513–14. Bibcode:1877AmJS...14..513M. doi:10.2475/ajs.s3-14.84.513. S2CID 130078453.
  20. ^ Carpenter, K.; Galton, P. M. (2001). "Othniel Charles Marsh and the Eight-Spiked Stegosaurus". In Carpenter, Kenneth (ed.). The Armored Dinosaurs. Indiana University Press. pp. 76–102. ISBN 978-0-253-33964-5.
  21. ^ Gedeon, Katie; Proudfoot, Nicholas; Young, Benjamin (2017). "Kazhdan-Lusztig polynomials of matroids: a survey of results and conjectures" (PDF). Séminaire Lotharingien de Combinatoire. 78B: 80. arXiv:1611.07474.
  22. ^ Zhu, Wandi S.; Litterman, Adam J.; Sekhon, Harshaan S.; Kageyama, Robin; Arce, Maya M.; Taylor, Kimberly E.; Zhao, Wenxue; Criswell, Lindsey A.; Zaitlen, Noah; Erle, David J.; Ansel, K. Mark (December 7, 2023). "GCLiPP: global crosslinking and protein purification method for constructing high-resolution occupancy maps for RNA binding proteins". Genome Biology. 24 (1): 281. doi:10.1186/s13059-023-03125-2. ISSN 1474-760X. PMC 10701951. PMID 38062486.
  23. ^ "Thagomizer". thagomizer.ucsf.edu. Retrieved January 12, 2024.