Nummulites: The biggest single cells that ever lived.

Anyone who has been to the great pyramids of the Giza Plateau next to Cairo in Egypt may have noticed 1-3 Cm lens shaped fossils within the limestone, both underfoot and in the buildings themselves. These are nummulites, the shells of faraminifera. The biggest known are ten cemtimetres wide, and they are used as index fossils to age sedimentary rocks. They were particularly common in the Paleocene and Eocene, a period of high sea levels before glaciation lowered them, when what is now Egypt was under the remnants of the Tethys sea. They are still around today, and were named after the Latin for little coin.

Loz

Image credit: Fozy Istvan, via chronique du temps universel.fr.

Nummulites

Foraminifera are an extremely diverse group of single-celled organisms which have existed in one form or another since the earliest Cambrian. Of the huge number of foraminifera species which have evolved throughout the last 540 million years, each has possessed its own distinctive shell morphology. These complex shells were developed as a way of sustaining their size as a single-celled organism, with the need to create as large a surface area as possible. Due to this widely varying morphology, different species of foraminifera provide an excellent tool for geologists to date a rock in which their shells are found, by matching its shape to the known dates of that species' existence. These are known as index fossils.

Nummulites, pictured above, are just one genus of foraminifera, and have had much greater involvement in history than most of their cousins.

Nummulites are thought to be the first foraminifera to have been described in literature; by Greek historian Herodotus in the 5th century B.C. Its name stems from the latin word 'nummulus', meaning coin. Although this is simply due to its shape, it is also widely speculated that the shells were used as a form of currency in ancient Egyptian society. With shells typically between 1.3 to 5 cm in diameter, the shells were perfect for this function.

The first nummulite described by Herodotus was in fact observed in a limestone block of the Egyptian pyramids. The Eocene limestones used to build the pyramids are riddled with nummulites, which would have accumulated in the shallow areas of the ancient Tethys sea. These nummulitic limestones are seen every day by the thousands of tourists who peruse the Egyptian monuments - be sure to keep an eye out if you ever visit!

A.G.C.

Scale: Nummulite shell at centre of photo has a diameter of 1.46 cm

Image credit: http://bit.ly/1LX9v7b

Mikrofosillerin Mikroskop Fotoğrafları (HD) - 2

Globigerina

Globoturucana

Hemigordius

Nummulites

Quinqueloculina

Rugoglobigerina

Tetrataxis