''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 ...
of the
Ediacaran biota; 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 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 umbrell ...
but some specimens seem to be distorted to accommodate adjacent specimens on the substrate, apparently indicating a
benthic (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 prec ...
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 the ...
),
Charnwood Forest (
England
England is a country that is part of the United Kingdom. It shares land borders with Wales to its west and Scotland to its north. The Irish Sea lies northwest and the Celtic Sea to the southwest. It is separated from continental Europe b ...
), 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-eig ...
), North
China,
Newfoundland, Northwest
Canada
Canada is a country in North America. Its ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, covering over , making it the world's second-largest country by tot ...
, Podolia (
Ukraine
Ukraine ( uk, Україна, Ukraïna, ) is a country in Eastern Europe. It is the second-largest European country after Russia, which it borders to the east and northeast. Ukraine covers approximately . Prior to the ongoing Russian inv ...
), 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 econ ...
Mountains (
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-eig ...
), 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
Ediacaran biota— 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 un ...
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.]
See also
*
List of Ediacaran genera
This is a list of all described Ediacaran genera, including the Ediacaran biota. It contains 227 genera.
References
{{reflist, 30em
*
Ediacaran
The Ediacaran Period ( ) is a geological period that spans 96 million years from the end ...
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