, the Nummuliten (lat. nummulus - small coin), in the vernacular also „Münz (EN) stones “mentioned, are circular or elliptically formed single-celled organisms from the group of the Kammerlinge (Foraminifera), which can reach a size of up to 10 cm in the diameter.
The Nummuliten (family Nummulitidae) belongs into the large order Rotaliida and is the most well-known Foraminiferen („flat amoebas “). With Nummuliten it acts around Grossforaminiferen, which can reach typically 1 to 2 cm in the diameter, exeptionally can it up to 10 centimeters be. This size and the circular shape of the housings unusual for a single-celled organism help the fossil Nummuliten to their name. They step for the first time in the highest chalk fossil into feature and experienced their bloom time in the early Tertiary period, here particularly in the Tethysmeer. In the sedimentary rocks of this time period this form-rich group is of great importance as guidance fossil. The rezenten (today living persons) Nummuliten inhabits the soil region (Benthal) of tropical and subtropical seas, preferentially within the flat coastal range.
The kalkigen bowls of the Nummuliten could accumulate themselves after their death in earth-history past to so large masses that they became rock-forming, so for example with the Nummulitenkalken from the old Tertiary period. Quarries in the proximity supplied the blocks from eozänem Nummulitenkalkstein with that approximately to 60% with of the pyramids by Gizeh were built. When Herodot Egypt visited, he regarded the Nummuliten as petrified lenses, remainders of the meals of the pyramid workers.