Nimbia (genus)

Nimbia is a common enigmatic discoidal form from Neoproterozoic, possibly into the Cambrian, and can be found from across the globe. Most researchers consider them to either be simple microbial colonies, equally simple cnidarians, or the holdfasts of a larger organism, such as those seen in the Petalonamae phylum.

Discovery

The first fossils of Nimbia were found from the Ediacaran aged Ustʹ Pinega Formation, on the Winter Coast (Zimnii Bereg) of the White Sea, Northwestern Russia, and described in 1980.

Etymology

The generic name Nimbia derives from the Latin word "Nimbus", to mean "halo", in reference to the rim seen in the original fossils.

The specific name for N. occlusa derives from the Latin word "occlusal", to mean "closed", in reference to the smooth appearance of the species. The specific name for N. dniesteri is derived from the Dniester River, which flows past the formation were the fossils specimens for this species were found.

Description

Nimbia occlusa is discoidal in overall shape, ranging from 15–40 mm (0.6–1.6 in) in diameter. It is usually flat, although some fossils may bear a central raised tubercle or a dimple, and the margin of the organism is also notably thick. There are also faint concentric annuli in some specimens, which can get up to 3–5 mm (0.1–0.2 in) wide, and are spaced from each other by 1.5–4 mm (0.1–0.2 in). For a long time, these fossils were considered to be the oldest know probable animals, although many studies done since have recovered older probable remains.