Nummulite
Nummulite. The cases show the typical planspiralig tortuous, round shape and chambered by partitions inner construction (frame 3 x 4 cm)
Nummulites ( Nummulitidae ), popularly known as " coin (s) stones ", are a family of circular or elliptically shaped single-celled organisms from the group of foraminifera ( Foraminifera ) in the order of the Rotaliida.
Description
The nummulites is large Foraminifera, which can typically reach 1-2 cm in diameter.
The largest extant species can reach up to 13 centimeters ( Cycloclypeus carpenteri ), fossil Nummulitidae reached a size of up to 16 centimeters. The housings are biconvex discs, multilocular and mostly flat spiral. The chamber walls form a complex with the Kiel canal system that is filled with cytoplasm.
Way of life
Nummulitidae among the so-called large Foraminifera live in warm shallow seas and accommodate non- diatoms turn endosymbionts ( zooxanthellae ). It is believed that their ontogeny lasts over 100 years.
System
The circular shape of the housing has helped the family to their name, from the Latin nummulus - small coin.
Today the group comprises only 11 species in eight genera:
- Nummulites
- Cycloclypeus
- Heterocyclina
- Heterostegina
- Operculina
- Operculinella
- Plan Operculina
- Planostegina
Extinct genera ( selection):
- Assilina
- Camerina
- Spiroclypeus
Fossil nummulites
The family occurs fossil in the upper chalk in appearance and had its heyday in the early Tertiary, here especially in the Tethys.
In the Paleogene ( Lower Tertiary ), the group was represented particularly rich in species and formed the so-called Nummulitenkalke from. The genera Assilina (†) and Nummullites are index fossils of the Tertiary.
The calcareous shells of Nummulites could after her death in geological past to accumulate such large masses that they were rock-forming, such as in the Nummulitenkalken from the Paleogene. Quarries in the vicinity supplied the blocks from eozänem Nummulitenkalkstein, were built with the approximately 60 % of the Pyramids of Giza. When Herodotus visited Egypt, he held the nummulites for petrified lenses, remains of meals of the pyramid workers. This interpretation as stone lenses is occupied also in Central Europe, for example in Guttaring in Carinthia, where you can find very easily countless nummulites in clay soil and a so-called field of stone lenses is reported.
In the foothills of the Alps in Bavaria Nummulitenkalksteine were used for historic buildings. These were the so-called Enzenauer marble and granite marble Rosenheim.
Swell
- Volker Storch, Ulrich Welsch: Short textbook of zoology. 8th Edition Oxford University Press, 2004, ISBN 3-8274-1399-0
- Johann Hohenegger, Elza Yordanova and Akio Hatta: Remarks on West Pacific Nummulitidae ( Foraminifera ) - The Journal of Foraminiferal Research, 30 ( 1 ), pp. 3-28