Thezygosphene-zygantrum articulation is an accessory joint between vertebrae found in severallepidosauromorph reptiles. Thispivot joint consists of a forward-facing, wedge-shapedprocess called thezygosphene, that fits in a depression on the rearside of the next vertebrae, called thezygantrum.[1] The zygosphene sits between theprezygapophysis in theneural arch, whereas the zygantrum sits between thepostzygapophysis.[2]
This joint is found insnakes,lacertids,teiids,Gymnophthalmids as well as in someiguanids andcordylids.[3] It is also found in several fossil groups such asplesiosaurians,nothosaurians andpachypleurosaurians.[4] It is absent in today'sMonitor lizard (Varanus), but occurs in fossil Varanids.[5]
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.[5]