Zygosphene-zygantrum articulation

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The zygosphene-zygantrum articulation is an accessory joint between vertebrae found in several lepidosauromorph reptiles. This pivot joint consists of a forward facing, wedge-shaped process called the zygosphene, that fits in a depression on the rearside of the next vertebrae, called the zygantrum.[1] The zygosphene sits between the prezygapophysis in the neural arch, whereas the zygantrum sits between the postzygapophysis.[2]

This joint is found in snakes, lacertids, teiids, Gymnophthalmids as well as in some iguanids and cordylids.[3] It is also found in several fossil groups such as plesiosaurians, nothosaurians and pachypleurosaurians.[4] It is absent in today's Monitor lizard (Varanus), but occurs in fossil Varanids.[5]

The zygosphen-zygantrum joint function to stabilize the vertebral column. While it permits horizontal and vertical movements of the vertebral column, it prevents rotations of the single vertebrae against each other.[5]

References

  1. ↑ Rieger, Gunde; Wilfried Westheide (2009-10-29). Spezielle Zoologie. Teil 2: Wirbel- oder Schädeltiere (in German). Springer DE. p. 381. ISBN 9783827420398. 
  2. ↑ Callaway, Jack M.; Elizabeth L. Nicholls (1997-03-12). Ancient Marine Reptiles. Academic Press. p. 125. ISBN 9780080527215. 
  3. ↑ Estes, Richard; Kevin de Queiroz, Jacques Gauthier (1988). "Phylogenetic Relationships within Squamata". In Richard J. Estes. Phylogenetic Relationships of the Lizard Families: Essays Commemorating Charles L. Camp. Stanford University Press. p. 166. ISBN 9780804714358. 
  4. ↑ Benton, Michael J. (2005). Vertebrate palaeontology (3. ed.). Blackwell Science. p. 150. ISBN 0-632-05637-1. 
  5. ↑ 5.0 5.1 Romer, Alfred Sherwood (1956). Osteology of the Reptiles. The University of Chicago Press. p. 256. ISBN 0-226-72487-5. 
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