''Eoandromeda'' is an

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 t ...

organism In biology, an organism () is any life, living system that functions as an individual entity. All organisms are composed of cells (cell theory). Organisms are classified by taxonomy (biology), taxonomy into groups such as Multicellular o ...

consisting of eight radial spiral arms, and known from two taphonomic modes: the standard

Ediacara type preservation Ediacaran type preservation relates to the dominant preservational mode in the Ediacaran period, where Ediacaran organisms were preserved as casts on the surface of microbial mats. Exceptional preservation All but the smallest fraction of th ...

in Australia, and as carbonaceous compressions from the

Doushantuo formation The Doushantuo Formation (formerly transcribed as Toushantuo or Toushantou, from ) is a geological formation in western Hubei, eastern Guizhou, southern Shaanxi, central Jiangxi, and other localities in China. It is known for the fossil Lagers ...

of China, where it is abundant.

Morphology

A few dozen

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 ...

specimens are known, ranging from about 1 to 4 cm in diameter; they are circular in outline and their eight arms, with closed ends, spiral either clockwise or counterclockwise. Ridges cut across both the inside and outside of the spiral arms. The arms of the Australian individuals are longer and more tightly coiled than those of the Chinese, despite the Australian individuals not attaining as large a diameter; they are more often kinked.

Affinity

The organism was first interpreted as a

trace fossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

, and has also been considered to represent an agglutinating

foraminifera Foraminifera (; Latin for "hole bearers"; informally called "forams") are single-celled organisms, members of a phylum or class of amoeboid protists characterized by streaming granular ectoplasm for catching food and other uses; and commonly ...

n. However, the discovery of the Chinese fossils, which have preserved organic matter, ruled out these interpretations, because the

Burgess shale type preservation The Burgess Shale of British Columbia is famous for its exceptional preservation of mid-Cambrian organisms. Around 69 other sites have been discovered of a similar age, with soft tissues preserved in a similar, though not identical, fashion. Additi ...

displayed required relatively robust organic material to start with. Its spiral form has also led to comparison with the fossil embryos also preserved in the Doushantuo formation; the exact purpose still remains out on this until intermediate forms are found. The organism bears a very superficial resemblance to

echinoderm An echinoderm () is any member of the phylum Echinodermata (). The adults are recognisable by their (usually five-point) radial symmetry, and include starfish, brittle stars, sea urchins, sand dollars, and sea cucumbers, as well as the s ...

ctenophore Ctenophora (; ctenophore ; ) comprise a phylum of marine invertebrates, commonly known as comb jellies, that inhabit sea waters worldwide. They are notable for the groups of cilia they use for swimming (commonly referred to as "combs"), and ...

s and to some of the other

Ediacara 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 sessil ...

, but it lacks sufficient physical characteristics to ascertain with any degree of certainty whether it is indeed an

animal Animals are multicellular, eukaryotic organisms in the Kingdom (biology), biological kingdom Animalia. With few exceptions, animals Heterotroph, consume organic material, Cellular respiration#Aerobic respiration, breathe oxygen, are Motilit ...

or not. If it is, it would be the earliest known fossil of an adult animal; and its anatomy is consistent with that expected from the earliest animals. However, it is not perfectly clear that it is an animal;

algae Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from ...

, the dominant constituent of the Doushantuo biota, cannot be ruled out, except that ''Eoandromeda'' seems a little too complex.

Taphonomic significance

In the Ediacaran (Vendian) period there are two biotas of multicellular organisms; as now understood, these biota do not generally share members, as was considered until recently: * Ediacara-type biota (it is in broad sense: Ediacara-, Nama-, Avalon-type ecological assemblage) it is community of the Metazoa and problematic organisms: ''

Dickinsonia ''Dickinsonia'' is an extinct genus of basal animal that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine. The individual ''Dickinsonia'' typically resembles a bilaterally symmetrical ribbed oval. Its a ...

'', ''

Yorgia ''Yorgia waggoneri'' is a discoid Ediacaran organism. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of . It is classified within the extinct animal phylum Proarti ...

'', ''

Kimberella ''Kimberella'' is an extinct genus of bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity with ...

'', ''

Charnia ''Charnia'' is a genus of frond-like lifeforms belonging to the Ediacaran biota with segmented, leaf-like ridges branching alternately to the right and left from a zig-zag medial suture (thus exhibiting glide reflection, or opposite isometry). T ...

'', ''

Charniodiscus ''Charniodiscus'' is an Ediacaran fossil that in life was probably a stationary filter feeder that lived anchored to a sandy sea bed. The organism had a holdfast, stalk and frond. The holdfast was bulbous shaped, and the stalk was flexible. The ...

'', ''

Cyclomedusa ''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 20 cm are known. The concentric dis ...

'', ''

Ediacaria ''Ediacaria'' is a fossil genus dating to the Ediacaran Period of the Neoproterozoic Era. Unlike most Ediacaran biota, which disappeared almost entirely from the fossil record at the end of the Period, ''Ediacaria'' fossils have been found ...

'', ''

Parvancorina ''Parvancorina'' is a genus of shield-shaped bilaterally symmetrical fossil animal that lived in the late Ediacaran seafloor. It has some superficial similarities with the Cambrian trilobite-like arthropods. Etymology The generic name is derived ...

'', ''

Pteridinium ''Pteridinium'' is an erniettomorph found in a number of Precambrian deposits worldwide. It is a member of the Ediacaran biota. Body plan The three-lobed body is generally flat such that only two lobes are visible. Each lobe consists of a number ...

'', ''

Rangea ''Rangea'' is a frond-like Ediacaran fossil with six-fold radial symmetry. It is the type genus of the rangeomorphs. ''Rangea'' was the first complex Precambrian macrofossil named and described anywhere in the world. ''Rangea'' was a centimetre- ...

'', '' Fractofusus'', ''

Tribrachidium ''Tribrachidium heraldicum'' is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. ''T. heraldicum'' is the best known member of the extinct group Trilobozoa. Etymology ...

'', '' Hiemalora'', palaeopascichnids and others. These organisms mainly are negative and positive imprints on the base of sandstone beds with the "elephant skin" and tubercle texture diagnostic of

microbial mat A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in desert ...

s (Ediacara-type preservation), sandy casts in the beds of sandstone (Nama-type preservation), Avalon-type preservation characterized imprints on the top mudstone surface covered by volcanic ash, and in Khatyspyt-type preservation the fossils are found in finely laminated to medium-bedded, nodular

bituminous limestone Bituminous limestone is limestone impregnated and sometimes deeply colored with bituminous matter derived from the decomposition of animal and plant remains entombed within the mass or in its vicinity. Uses The amount of bituminous matter or asph ...

s. *Miaohe-type biota characterizes assemblage of

algal Algae ( , ; : alga ) are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from un ...

macrofossils: ''Beltanelloides'', '' Mezenia'', ''Sinospongia'', ''Jiuqunaoella'', ''Grypania'', ''Liulingjitaenia'', ''

Tawuia ''Tawuia'' is a millimetric disc-shaped, most likely multicellular macrofossil from the Neoproterozoic. It is considered to be synonymous with ''Chuaria'' and ''Longfengshania'', which, in turn, are thought to represent different life stages o ...

'', '' Calyptrina'', ''Cucullus'' and others. These fossils are of the form of flat organic carbonaceous films; it is shadow left by organic matter of the organism flesh (it is looks like of the

). Trying to relate organisms that are preserved in the two modes is immensely problematic, because they preserve such different parts of organisms; the imprints preserve a casts of the organism's outline, whereas the carbonaceous films display a shadow left by any resistant organic matter. This has made relating the two taphonomic types very difficult: ''Eoandromeda'' is one of the few organisms which can convincingly be compared in both taphonomic modes. Such cases of preservation are known also for organisms related to the ''

Anfesta ''Anfesta stankovskii'' is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa. Etymology The generic and specific names of the ''Anfesta stankovskii'' hon ...

Albumares ''Albumares brunsae'' is a tri-radially symmetrical fossil animal that lived in the late Ediacaran seafloor. It is a member of the extinct group Trilobozoa. Etymology The generic name ''Albumares'' derives from the Latin ''Mare Album'' (White S ...

''-like fossils from the Doushantuo Formation, for '' Beltanelloides sorichevae'' from the Lyamtsa Formation of the

White Sea The White Sea (russian: Белое море, ''Béloye móre''; Karelian and fi, Vienanmeri, lit. Dvina Sea; yrk, Сэрако ямʼ, ''Serako yam'') is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is s ...

area,

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-eigh ...

and Doushantuo Formation, and possible for '' Cyclomedusa davidi'' from Perevalok Formation of the Central Urals.

References

{{Taxonbar, from=Q5381582 Enigmatic animal taxa Ediacaran life Fossils of China

Morphology

Affinity

Taphonomic significance

See also

References