Thagomizer

---

title: "Thagomizer" type: doc version: 1 created: 2026-02-28 author: "Wikipedia contributors" status: active scope: public tags: ["dinosaur-anatomy", "the-far-side", "stegosauria", "1980s-neologisms", "words-originating-in-fiction"] description: "Spike arrangement on stegosaur tails" topic_path: "science/biology" source: "https://en.wikipedia.org/wiki/Thagomizer" license: "CC BY-SA 4.0" wikipedia_page_id: 0 wikipedia_revision_id: 0

::summary Spike arrangement on stegosaur tails ::

::figure[src="https://upload.wikimedia.org/wikipedia/commons/2/27/Thagomizer_01.jpg" caption="Thagomizer on a mounted ''[[Stegosaurus]]'' tail"] ::

A thagomizer () is the distinctive arrangement of spike-shaped osteoderms on the tails of some 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

::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/65/Thagomizer.png" caption="Far Side]]'' cartoon is the source of the term ''thagomizer''." 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.""] ::

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".

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. Thagomizer has since been adopted as an informal anatomical term and is used by the Smithsonian Institution, the Dinosaur National Monument, the book The Complete Dinosaur and the BBC documentary series Planet Dinosaur. The term has also appeared in some scientific papers describing stegosaurs and related dinosaurs.

Paleobiology

::figure[src="https://upload.wikimedia.org/wikipedia/commons/6/65/Kentrosaurus_aethiopicus_01.jpg" caption="Skeleton of ''[[Kentrosaurus]]''"] ::

Some stegosaurs such as Kentrosaurus do not have a distinct "thagomizer" consisting 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 osteoderms, which are also spike-like, unlike the broad plate-like osteoderms on the back of Stegosaurus.

There has been debate about whether the thagomizer was used simply for display, as posited by Gilmore in 1914, 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. 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.

::figure[src="https://upload.wikimedia.org/wikipedia/commons/f/fa/Thagomizer.tif" caption="''Allosaurus'' tail [[vertebra]] with a hole matching a thagomizer spine"] ::

In 2001, a study of thagomizers by McWhinney et al. 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. This usage of the thagomizer would be similar to defensive behaviors in some extant lizards with tail spikes, such as the giant girdled lizard.

The species of stegosaur known as Stegosaurus stenops had four dermal spikes, each about 60 - 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. 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.

Other uses

Mathematics

::figure[src="https://upload.wikimedia.org/wikipedia/commons/7/73/Thagomizer-graph.svg" caption="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.

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 CLIP-Seq (Cross-linking and immunoprecipitation) data.

References

References

1. Black, Riley. (March 30, 2011). "Watch Out For That Thagomizer!".
2. (July 8, 2006). "The word: Thagomizer".
3. Holtz, Thomas R. Jr.. (2007). "Dinosaurs: the Most Complete, Up-To-Date Encyclopedia for Dinosaur Lovers of All Ages". Random House.
4. "Stegosaurus Changes". Smithsonian National Museum of Natural History, Department of Paleobiology.
5. (1999). "Stegosaurs". Indiana University Press.
6. (November 26, 2015). "Fight For Life".
7. (2011). "Defense capabilities of ''Kentrosaurus aethiopicus'' Hennig, 1915". Palaeontologia Electronica.
8. (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.
9. (December 1, 2021). "Bizarre tail weaponry in a transitional ankylosaur from subantarctic Chile". Nature.
10. (2022). "New thyreophoran dinosaur material from the Early Jurassic of northeastern Germany". PalZ.
11. (2024). "''Miragaia'' tail biomechanics and defences. Evaluation of the tail mobility and resistance to loadings and collisions". Rivista Italiana di Paleontologia e Stratigrafia.
12. (April 16, 2025). "The function and Evolution of Stegosaur Osteoderms and Hypothesized Sexual Dimorphism in Hesperosaurus".
13. Gilmore, C. W.. (1914). "Osteology of the armored Dinosauria in the United States National Museum, with special reference to the genus ''Stegosaurus''". Government Printing Office.
14. Bakker, R. T.. (June 2020). "The Dinosaur Heresies". William Morrow.
15. Naish, Darren. (2010). "Heinrich's digital Kentrosaurus: the SJG stegosaur special, part II". Tetrapod Zoology.
16. (2001). "The Armored Dinosaurs". Indiana University Press.
17. (2005). "The Carnivorous Dinosaurs". [[Indiana University Press]].
18. (January 2025). "Review of osteoderm function and future research directions". Journal of Zoology.
19. Carpenter, Kenneth. (1998). "Armor of ''Stegosaurus stenops'', and the taphonomic history of a new specimen from Garden Park, Colorado". Modern Geology.
20. (1877). "A new order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains". American Journal of Science.
21. (2001). "The Armored Dinosaurs". Indiana University Press.
22. (2017). "Kazhdan-Lusztig polynomials of matroids: a survey of results and conjectures". Séminaire Lotharingien de Combinatoire.
23. (December 7, 2023). "GCLiPP: global crosslinking and protein purification method for constructing high-resolution occupancy maps for RNA binding proteins". Genome Biology.
24. "Thagomizer".

::callout[type=info title="Wikipedia Source"] This article was imported from Wikipedia and is available under the Creative Commons Attribution-ShareAlike 4.0 License. Content has been adapted to SurfDoc format. Original contributors can be found on the article history page. ::