nummulites

Nummulites are a genus of large, flat, lenticular or discoidal foraminifera, which are single-celled marine organisms. These fossils are characterized by their coiled, chambered shells, typically resembling a small coin, which is where their name originates from (nummus meaning coin in Latin). Nummulites lived in shallow, warm seas during the Paleogene and Neogene periods, particularly abundant in the Eocene epoch. Their shells are made of calcium carbonate and can vary in size from a few millimeters to over 10 centimeters in diameter.

The internal structure of nummulite shells is complex, featuring numerous small chambers arranged in a spiral pattern. This structure is key to their classification and study. Nummulites are found globally, with significant deposits in the Mediterranean region, particularly in Egypt, where they are famously found in the pyramids, and in parts of Asia. Their widespread distribution and distinct morphology make them important index fossils for correlating rock strata from the Paleogene period.

The life cycle of nummulites involved both a sexual and asexual generation, a common characteristic of foraminifera. The large shells we find as fossils represent the tests, or exoskeletons, of these organisms. While once thought to be mollusks or even coral, they are now definitively classified as protists. The study of nummulites provides valuable insights into ancient marine environments, paleogeography, and the evolution of life.