# Orbitolina

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***Orbitolina*** is an [extinct](/source/Extinct) [genus](/source/Genus) of [foraminifera](/source/Foraminifera) belonging to the order [Textulariida](/source/Textulariida) and family [Orbitolinidae](/source/Orbitolinidae). Fossils of this genus are widely found in beds deposited in the [Tethys Ocean](/source/Tethys_Ocean) ranging from [Aptian](/source/Aptian) ([early Cretaceous](/source/Early_Cretaceous))[4] to [Cenomanian](/source/Cenomanian) (early [Late Cretaceous](/source/Late_Cretaceous)) in age.[3] It has been used as a shallow [carbonate platform](/source/Carbonate_platform) [facies](/source/Facies_(geology)) marker[4] and as a Cretaceous [index fossil](/source/Index_fossil).[3]

The test of the organism has the shape of a cone, with the proloculus (initial chamber) at the apex of the cone and increasingly large cuplike chambers forming the remainder of the test. Each chamber is further subdivided by numerous partitions.[3]

## References

1. Schlagintweit, F. & Wagreich, M. (2005). ["Micropaleontology of "Orbitolina Beds" of Lower Austria (Branderfleck Formation, Lower Cenomanian)"](https://www.zobodat.at/pdf/JbGeolReichsanst_145_0115-0125.pdf). *Jahbruch der Geologischen Bundenstalt*. **145** (1): 115–125. Retrieved 25 October 2021.

1. Buckman, J. O. (March 1997). "An unusual new trace fossil from the Lower Carboniferous of Ireland: Intexalvichnus magnus". *Journal of Paleontology*. **71** (2): 316–324. [doi:10.1017/S0022336000039226](https://doi.org/10.1017/S0022336000039226)

1. Douglass, R.C. (1960). "The Foraminiferal Genus Orbitolina in North America". *United States Geological Survey Professional Paper*. **333**. Professional Paper. [doi:10.3133/pp333](https://doi.org/10.3133/pp333)

1. Vilas, Lorenzo; Masse, Jean Pierre; Arias, Consuelo (December 1995). ["Orbitolina episodes in carbonate platform evolution: the early Aptian model from SE Spain"](https://eprints.ucm.es/26804/1/1-s2.0-00_01.pdf). *Palaeogeography, Palaeoclimatology, Palaeoecology*. **119** (1–2): 35–45. [Bibcode:1995PPP...119...35V](https://ui.adsabs.harvard.edu/abs/1995PPP...119...35V). [doi:10.1016/0031-0182(95)00058-5](https://doi.org/10.1016/0031-0182(95)00058-5)

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