Nummulites

Article By:

Loelich, Alfred R., Jr. Department of Earth and Space Sciences, University of California, Los Angeles, California.

Hallock, Pamela College of Marine Science, University of South Florida, St. Petersburg, Florida.

Last reviewed:August 2020

DOI:https://doi.org/10.1036/1097-8542.462000

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• Nummulites, published June 2014:Download PDF Get Adobe Acrobat Reader

A genus of unicellular shelled foraminifers (family Nummulitidae). Members of the genus Nummulites (termed nummulites) are single-celled protoctists (protozoa) of the Foraminifera taxon (which is typically regarded as a phylum or subphylum, depending on the exact classification scheme). There are both extinct and living nummulites. The shells of Nummulites (see illustration) and other large, internally complex foraminifers commonly occurred in rock-forming abundances on continental shelves and around oceanic islands throughout subtropical and tropical regions during the Cenozoic. Resulting limestones are important hydrocarbon reservoirs, especially from the Philippines and Indonesia westward to Trinidad and Venezuela. Nummulitic limestones have been used as building materials around the Mediterranean region; for example, the pyramids of Egypt were constructed of blocks of Eocene age. Nummulite shells are useful stratigraphic and paleoenvironmental indicators, and the extinct species are notable index fossils; the Paleogene was formerly known as the Nummulitic Period. See also: Cenozoic; Extinction (biology); Foraminiferida; Index fossil; Limestone; Protozoa

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