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'''.<ref name="spezzoolgie"/> The zygosphene sits between the prezygapophysis in the neural arch, whereas the zygantrum sits between the postzygapophysis.<ref name="callaway1997"/>
This joint is found in snakes, lacertids, teiids, Gymnophthalmids as well as in some iguanids and cordylids.<ref name="estes1998"/> It is also found in several fossil groups such as plesiosaurians, nothosaurians and pachypleurosaurians.<ref name="benton2005"/> It is absent in today's Monitor lizard (''Varanus''), but occurs in fossil Varanids.<ref name="romer1956"/>
The zygosphene-zygantrum joint's function is 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.<ref name="romer1956"/>
==See also== * Hyposphene-hypantrum articulation, in the Archosauromorpha
==References== <references> <ref name="spezzoolgie">{{Cite book| publisher = Springer DE| isbn = 9783827420398| last1 = Rieger| first1 = Gunde| first2 = Wilfried |last2=Westheide| title = Spezielle Zoologie. Teil 2: Wirbel- oder Schädeltiere| language=de| date = 2009-10-29|page=381}}</ref> <ref name="callaway1997">{{Cite book| publisher = Academic Press| isbn = 9780080527215| last1 = Callaway| first1 = Jack M. |first2=Elizabeth L. |last2=Nicholls| title = Ancient Marine Reptiles| url = https://archive.org/details/ancientmarinerep00call| url-access = limited| date = 1997-03-12|page=[https://archive.org/details/ancientmarinerep00call/page/n171 125]}}</ref> <ref name="estes1998">{{Cite book |editor=Richard J. Estes |last1=Estes |first1=Richard |first2=Kevin |last2=de Queiroz |first3=Jacques |last3=Gauthier |title=Phylogenetic Relationships of the Lizard Families: Essays Commemorating Charles L. Camp |chapter=Phylogenetic Relationships within Squamata |page=166|publisher=Stanford University Press |isbn=9780804714358 |year=1988}}</ref> <ref name="benton2005">{{Cite book |first=Michael J. |last=Benton |authorlink = Michael Benton|title=Vertebrate palaeontology |url=https://archive.org/details/vertebratepalaeo00bent_663 |url-access=limited |publisher=Blackwell Science |year=2005 |edition=3. |isbn=0-632-05637-1 |page=[https://archive.org/details/vertebratepalaeo00bent_663/page/n161 150]}}</ref> <ref name="romer1956">{{cite book |last=Romer |first=Alfred Sherwood |title=Osteology of the Reptiles |publisher=The University of Chicago Press |isbn=0-226-72487-5 |year=1956 |page=256}}</ref> </references>
Category:Reptile anatomy