Thagomizer
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The thagomizer is the arrangement of four to ten spikes on the tail of particular dinosaurs, like the famous Stegosaurus, in the clade Stegosauria. The tail arrangement is believed to have been a defensive weapon against predators. The thagomizer is also called the tail spikes.
The term "thagomizer" originated as a joke from a Far Side comic strip by Gary Larson, in which a group of cavemen in a lecture hall are taught by their caveman professor that the spikes were named in honor of "the late Thag Simmons". The implication is that the Thagomizer was responsible for Thag's death. This is a comic anachronism on multiple levels; the use of slide projectors and surnames is overshadowed by the implication that cavemen co-existed with dinosaurs.
Whatever was the original word for the spiked tail of Stegosaurus, if it indeed ever had one, "thagomizer" has, since the Far Side publication, been adopted as a genuine anatomical term[1] and is used by multiple palaeontological authorities, including the Smithsonian Institution[2].
[edit] Palaeobiology
There has been debate about whether the tail spikes were used for display only, as posited by Gilmore in 1914 [3] or used as a weapon. Robert Bakker noted the tail was likely to have been much more flexible than other dinosaurs as it lacked ossified tendons, thus lending credence to the idea of the tail as a weapon. He also observed that Stegosaurus could have manoeuvred 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 [4].
More recently, a study of tail spikes, by McWhinney et al.,[5] which showed a high incidence of trauma-related damage, confirms the spikes were indeed used in combat.
Stegosaurus stenops had four dermal spikes, each about 60-90 cm (2 to 3 feet) 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, 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.[6] [7]
[edit] See also
[edit] Footnotes
- ^ The word: Thagomizer New Scientist 08 July 2006
- ^ Stegosaurus Changes. Smithsonian National Museum of Natural History, Department of Paleobiology. Retrieved on 2006-03-07.
- ^ Gilmore CW (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).
- ^ Bakker RT (1986). The Dinosaur Heresies. william Morrow, New York.
- ^ McWhinney LA, Rothschild BM & Carpenter K (2001). “Posttraumatic Chronic Osteomyelitis in Stegosaurus dermal spikes”, Carpenter, Kenneth(ed) The Armored Dinosaurs. Indiana University Press, 141–156. ISBN 0-253-33964-2.
- ^ Marsh OC (1877). "A new order of extinct Reptilia (Stegosauria) from the Jurassic of the Rocky Mountains". American Journal of Science 3 (14): 513–514.
- ^ Carpenter K & Galton PM (2001). “Othniel Charles Marsh and the Eight-Spiked Stegosaurus”, Carpenter, Kenneth(ed) The Armored Dinosaurs. Indiana University Press, 76–102. ISBN 0-253-33964-2.
- Holtz, T.R., (2000) "Classification and Evolution of the Dinosaur Groups" (pp140-168) in The Scientific American Book of Dinosaurs, edited by Gregory S. Paul, New York:St Martin's Press ISBN 0-312-26226-4
