# Eoandromeda

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{{Short description|Genus of Ediacaran animal}}
{{Speciesbox
| fossil_range = [Ediacaran](/source/Ediacaran), approx. {{fossil range|580|550}}
| image = Eoandromeda octobrachiata.png
| image_caption = ''Eoandromeda octobrachiata'' from the Tongshan Lagerstätte, Dengying Formation, China
| genus = Eoandromeda
| species = octobrachiata
| authority = Tang, Yin, Bengtson, Liu, Wang and Gao, 2008
}}

'''''Eoandromeda''''' is an [Ediacaran](/source/Ediacaran) [organism](/source/Ediacara_biota) consisting of eight radial spiral arms, and known from two [taphonomic modes](/source/Taphonomy): the standard [Ediacara type preservation](/source/Ediacara_type_preservation) in Australia, and as carbonaceous compressions from the [Doushantuo Formation](/source/Doushantuo_Formation) of China,<ref name=Zhu2008>{{cite journal |author1=Maoyan Zhu |author2=James G. Gehling |author3=Shuhai Xiao |author4=Yuanlong Zhao |author5=Mary L. Droser | year = 2008| title = Eight-armed Ediacara fossil preserved in contrasting taphonomic windows from China and Australia| journal = Geology| volume = 36| issue = 11| pages = 867–870| doi = 10.1130/G25203A.1| url = http://geology.geoscienceworld.org/cgi/content/abstract/36/11/867|bibcode = 2008Geo....36..867Z | url-access = subscription}}</ref>
where it is abundant.<ref>{{cite journal| journal = Journal of China University of Geosciences| volume =  19| issue = 3| pages = 200–206| date = June 2008 | issn = 1002-0705| title = Megascopic Symmetrical Metazoans from the Ediacaran Doushantuo Formation in the Northeastern Guizhou, South China|author1=Wang Yue |author2=Wang Xunlian |author3=Huang Yuming | doi = 10.1016/S1002-0705(08)60039-4}}</ref>

==Morphology==
thumb|left|Artist restoration
A few dozen [fossil](/source/fossil) specimens are known, ranging from about 1 to 4&nbsp;cm in diameter; they are circular in outline and their eight arms, with closed ends, spiral either clockwise or counterclockwise.<ref name=Zhu2008/>
Ridges cut across both the inside and outside of the spiral arms.<ref name=Zhu2008/>  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](/source/trace_fossil), and has also been considered to represent an agglutinating [foraminifera](/source/foraminifera)n.  However, the discovery of the Chinese fossils, which have preserved organic matter, ruled out these interpretations, because the [Burgess shale type preservation](/source/Burgess_shale_type_preservation) displayed required relatively robust organic material to start with.<ref name=Zhu2008/>  Its spiral form has also led to comparison with the [fossil embryos](/source/fossil_embryos) also preserved in the Doushantuo Formation; the exact purpose still remains out on this until intermediate forms are found.<ref name=Zhu2008/>

The organism bears a very superficial resemblance to [echinoderm](/source/echinoderm)s, [ctenophore](/source/ctenophore)s and to some of the other [Ediacara biota](/source/Ediacara_biota), but it lacks sufficient physical characteristics to ascertain with any degree of certainty whether it is indeed an [animal](/source/animal) or not.<ref name=Zhu2008/>  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.<ref name=Zhu2008/>  However, it is not perfectly clear that it is an animal; [algae](/source/algae), the dominant constituent of the Doushantuo biota, cannot be ruled out, except that ''Eoandromeda'' seems a little too complex.<ref name=Zhu2008/>

==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](/source/Dickinsonia)'', ''[Yorgia](/source/Yorgia)'', ''[Kimberella](/source/Kimberella)'', ''[Charnia](/source/Charnia)'', ''[Charniodiscus](/source/Charniodiscus)'', ''[Cyclomedusa](/source/Cyclomedusa)'', ''[Ediacaria](/source/Ediacaria)'', ''[Parvancorina](/source/Parvancorina)'', ''[Pteridinium](/source/Pteridinium)'', ''[Rangea](/source/Rangea)'', ''[Fractofusus](/source/Fractofusus)'', ''[Tribrachidium](/source/Tribrachidium)'', ''[Hiemalora](/source/Hiemalora)'', [palaeopascichnids](/source/Palaeopascichnida) 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](/source/microbial_mat)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](/source/bituminous_limestone)s.
*Miaohe-type biota characterizes assemblage of [algal](/source/algal) macrofossils: ''Beltanelloides'', ''[Mezenia](/source/Mezenia)'', ''Sinospongia'', ''Jiuqunaoella'', ''Grypania'', ''Liulingjitaenia'', ''[Tawuia](/source/Tawuia)'', ''[Calyptrina](/source/Calyptrina_striata)'', ''Cucullus'' and others.<ref name= Xiao_et_al_2002>{{cite journal| author = Xiao, S.| author2 = Yuan, X.| author3 = Steiner, M.| author4 = Knoll, A.H.| year = 2007| title = Macroscopic carbonaceous compressions in a terminal Proterozoic shale: A systematic reassessment of the Miaohe biota: South China| journal = Journal of Paleontology| volume = 76| pages = 347–376| url = http://www.paleo.geos.vt.edu/Shuhai/Reprints/XiaoMiaoheBiotaJP2002.pdf| doi = 10.1666/0022-3360(2002)076<0347:MCCIAT>2.0.CO;2| issn = 0022-3360| issue = 2| access-date = 2008-11-15| archive-date = 2011-07-18| archive-url = https://web.archive.org/web/20110718134442/http://www.paleo.geos.vt.edu/Shuhai/Reprints/XiaoMiaoheBiotaJP2002.pdf| url-status = dead}}</ref><ref name= Grazhdankin_et_al_2007>{{cite journal| author = D. V. Grazhdankin |author2=K. E. Nagovitsin |author3=A.V. Maslov| year = 2007| title = Late Vendian Miaohe-type Ecological Assemblage of the East European Platform| journal = Doklady Earth Sciences| volume = 417| issue = 8| pages = 1183–1187| doi = 10.1134/S1028334X07080107| bibcode=2007DokES.417.1183G}}</ref> 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 [Burgess shale type preservation](/source/Burgess_shale_type_preservation)).

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](/source/Anfesta)-[Albumares](/source/Albumares)''-like fossils from the Doushantuo Formation, for ''[Beltanelloides sorichevae](/source/Beltanelloides)'' from the [Lyamtsa Formation](/source/Lyamtsa_Formation) of the [White Sea](/source/White_Sea) area, [Russia](/source/Russia)<ref name= Leonov_2007>{{cite journal| author = M. V. Leonov| year = 2007| title = Comparative taphonomy of Vendian genera ''Beltanelloides'' and ''Nemiana'': taxonomy and lifestyle| journal = Geological Society, London, Special Publications| volume = 286| pages = 259–267| url = http://sp.lyellcollection.org/cgi/content/abstract/286/1/259| doi = 10.1144/SP286.18| issue=1|bibcode = 2007GSLSP.286..259L | url-access = subscription}}</ref> and Doushantuo Formation,<ref name= Xiao_et_al_2002/> and possible for ''[Cyclomedusa davidi](/source/Cyclomedusa)'' from Perevalok Formation of the [Central Urals](/source/Urals).<ref name= Grazhdankin_et_al_2007/>

==See also==
* [List of Ediacaran genera](/source/List_of_Ediacaran_genera)

==References==
{{Reflist}}

{{Taxonbar|from=Q20677586|from2=Q5381582}}

Category:Enigmatic prehistoric animal genera
Category:Ediacaran life
Category:Fossils of China
Category:Monotypic prehistoric animal genera

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Adapted from the Wikipedia article [Eoandromeda](https://en.wikipedia.org/wiki/Eoandromeda) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Eoandromeda?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.