Cyclomedusa
Encyclopedia
Cyclomedusa is a circular fossil
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 20cm 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
-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
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
.
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
beds in Ediacara (Australia
), Finnmark (Norway
), Charnwood Forest
(England
), Olenek (Russia
), North China
, Newfoundland, Northwest Canada
, Podolia (Ukraine
), the Ural Mountains (Russia
), the White Sea (Russia), and Sonora (Mexico
). 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 animal phyla appeared. Cyclomedusa has no known relatives.
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
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 20cm 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
Pineapple
Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
-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
Ediacaran
The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...
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
Jellyfish are free-swimming members of the phylum Cnidaria. Medusa is another word for jellyfish, and refers to any free-swimming jellyfish stages in the phylum Cnidaria...
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 taxon
Form classification is the classification of organisms based on their morphology, which does not necessarily reflect their biological relationships...
.
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
Neoproterozoic
The Neoproterozoic Era is the unit of geologic time from 1,000 to 542.0 ± 1.0 million years ago. The terminal Era of the formal Proterozoic Eon , it is further subdivided into the Tonian, Cryogenian, and Ediacaran Periods...
beds in Ediacara (Australia
Australia
Australia , officially the Commonwealth of Australia, is a country in the Southern Hemisphere comprising the mainland of the Australian continent, the island of Tasmania, and numerous smaller islands in the Indian and Pacific Oceans. It is the world's sixth-largest country by total area...
), Finnmark (Norway
Norway
Norway , officially the Kingdom of Norway, is a Nordic unitary constitutional monarchy whose territory comprises the western portion of the Scandinavian Peninsula, Jan Mayen, and the Arctic archipelago of Svalbard and Bouvet Island. Norway has a total area of and a population of about 4.9 million...
), Charnwood Forest
Charnwood Forest
Charnwood Forest is an upland tract in north-western Leicestershire, England, bounded by Leicester, Loughborough, and Coalville. The area is undulating, rocky and picturesque, with barren areas. It also has some extensive tracts of woodland; its elevation is generally 600 ft and upwards, the area...
(England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
), Olenek (Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
), North China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
, Newfoundland, Northwest Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
, Podolia (Ukraine
Ukraine
Ukraine is a country in Eastern Europe. It has an area of 603,628 km², making it the second largest contiguous country on the European continent, after Russia...
), the Ural Mountains (Russia
Russia
Russia or , officially known as both Russia and the Russian Federation , is a country in northern Eurasia. It is a federal semi-presidential republic, comprising 83 federal subjects...
), the White Sea (Russia), and Sonora (Mexico
Mexico
The United Mexican States , commonly known as Mexico , is a federal constitutional republic in North America. It is bordered on the north by the United States; on the south and west by the Pacific Ocean; on the southeast by Guatemala, Belize, and the Caribbean Sea; and on the east by the Gulf of...
). 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 animal phyla appeared. Cyclomedusa has no known relatives.