Nummulites and discocyclina

Marine organisms that lived on tropical sea-beds

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These images show micro fossils of marine organisms whose size can vary from a few millimetres to two centimetres.

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They are part of a large group that includes multiple species of shapes that vary widely: formanifera. These are two of the largest that ever populated the seas of our planet.

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They are called nummulites, and those with a lozenge shape apparently consisted of wide concentric bands, with an eye at the centre.

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Those with a historiated appearance are called discocyclina, often very elongated or sometimes rounded and with elongated extremities.

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Although some nummulites could reach dimensions of more than 10cm, they are single-celled organisms.

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They live on the bed of a tropical sea that is several tens of metres deep, and it is believed that they require light to survive.

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In the images, we see them dissected, but when they are found complete they have the appearance of a stone circle. It is actually the fossilised shell of the organism, which is calcite, that we find. 

Nummulites or “stone coins”, these fossils take their name from their appearance. The ones in these photos are smaller; isolated, they would resemble a lentil.

Name: Limestone to macroforaminiferi
Type of rock: Carbonatic sedimentary rock
Minerals: Calcite
Fossils: foraminifera (nummulites, discocycline, others), red algae, echinoderms, molluscs
Location: torbole (N 45° 52’03.2″ E 010° 52’53.0″)
Formation: Limestone of Torbole
Age: Middle ecocene (about 56-38 million years)
Depositional environment: shallow Sea (a few tens of meters), tropical

curiosity

Did you know that these fossils are called Fossils guide and help scientists to date rocks.