''Cyclomedusa'' is a circular

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

of the

Ediacaran biota The Ediacaran (; formerly Vendian) biota is a taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-shaped, mostly sessile ...

; it has a circular bump in the middle and as many as five circular growth ridges around it. Many specimens are small, but specimens in excess of 20 cm are known. The concentric disks are not necessarily circular, especially when adjacent individuals interfere with each other's growth. Many radial segment lines — somewhat

pineapple The pineapple (''Ananas comosus'') is a tropical plant with an edible fruit; it is the most economically significant plant in the family Bromeliaceae. The pineapple is indigenous to South America, where it has been cultivated for many centuri ...

-like — extend across the outer disks. A few specimens show what might be a stem extending from the center in some direction or other. ''Cyclomedusa'' is widely distributed in

Ediacaran The Ediacaran Period ( ) is a geological period that spans 96 million years from the end of the Cryogenian Period 635 million years ago (Mya), to the beginning of the Cambrian Period 538.8 Mya. It marks the end of the Proterozoic Eon, and th ...

strata, with a number of species described. It has also been found in sediments dating to the Mayanian (~). ''Cyclomedusa'' was originally thought to be a

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella ...

but some specimens seem to be distorted to accommodate adjacent specimens on the substrate, apparently indicating a

benthic The benthic zone is the ecological region at the lowest level of a body of water such as an ocean, lake, or stream, including the sediment surface and some sub-surface layers. The name comes from ancient Greek, βένθος (bénthos), meaning "t ...

(bottom-dwelling) creature. The markings do not match the musculature pattern of modern jellyfish. The fossils have been conjectured to represent a holdfast for some stalked form — possibly an octacorallian, or something else entirely. Alternatively, it was thought that the described species actually represent different modes of preservation for one organism or that several different organisms have been grouped together under one name as a

form taxon Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships. Form classification, generally restricted to palaeontology, reflects uncertainty; the goal of s ...

. It is now suggested that ''Cyclomedusa'' was a microbial colony; D. Grazhdankin reinterprets the concentric rings and radial structures as comparable to those seen in modern-day microbial colonies exposed to homogeneously distributed environmental conditions. ''Cyclomedusa'' is known from

Neoproterozoic The Neoproterozoic Era is the unit of geologic time from 1 billion to 538.8 million years ago. It is the last era of the Precambrian Supereon and the Proterozoic Eon; it is subdivided into the Tonian, Cryogenian, and Ediacaran periods. It is pre ...

beds in Ediacara ( Australia), Finnmark (

Norway Norway, officially the Kingdom of Norway, is a Nordic country in Northern Europe, the mainland territory of which comprises the western and northernmost portion of the Scandinavian Peninsula. The remote Arctic island of Jan Mayen and th ...

), Charnwood Forest ( England), Olenek (

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eight ...

), North China,

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

, Northwest Canada, Podolia ( Ukraine), the

Ural Ural may refer to: *Ural (region), in Russia and Kazakhstan *Ural Mountains, in Russia and Kazakhstan *Ural (river), in Russia and Kazakhstan *Ual (tool), a mortar tool used by the Bodo people of India *Ural Federal District, in Russia *Ural econo ...

Mountains (

), the White Sea (Russia), and Sonora (

Mexico Mexico (Spanish: México), officially the United Mexican States, is a country in the southern portion of North America. It is bordered to the north by the United States; to the south and west by the Pacific Ocean; to the southeast by Guatema ...

). It is regarded as a member of the

— a group of somewhat obscure organisms that thrived just before most of the modern

multicellular A multicellular organism is an organism that consists of more than one cell, in contrast to unicellular organism. All species of animals, land plants and most fungi are multicellular, as are many algae, whereas a few organisms are partially uni ...

animal phyla appeared. ''Cyclomedusa'' has no known relatives.The few Ediacaran biota that survived into the Cambrian are discussed by Conway Morris 1993 and Narbonne 1998. However, if Cyclomedusa was a microbial colony, related microbes may be extant.

References

External links

(University of California at Berkeley) Cyclomedusa
{{Taxonbar, from=Q2561750 Enigmatic prehistoric animal genera White Sea fossils Fossil taxa described in 1947 Ediacaran life

See also

References

External links