Ovatoscutum

Ovatoscutum
Cast of Ovatoscutum concentricium
Scientific classification
Kingdom:	Animalia
Phylum:	Proarticulata
Genus:	Ovatoscutum Glaessner & Wade, 1966
Species
O. concentricium Glaessner & Wade, 1966

Schematic reconstruction of Ovatoscutum concentricium

Ovatoscutum is one of many enigmatic organism known from Ediacaran deposites of the Flinders Ranges, Australia and the White Sea area, Russia. This genera contains one species, Ovatoscutum concentricium.

This fossil have form of a rounded shield, sculptured with strong concentric corrugation/ribs, which weakens adjacent to a triangular neckline. A suture-like zone extends through the centre from the tip of the neckline towards the opposite margin. The ribs become wider towards the periphery.^[1][2]

Ovatoscutum was first described by Martin Glaessner and Mary Wade in 1966 and with doubt has been interpreted as a chondrophoran pneumatophore. This idea was based on some similarity of Ovatoscutum with Devonian Plectodiscus that was interpreted as velellid float (pneumatophore) and with modern chondrophoran pneumatophore Velella.^[1] Thus the speculative suggestion is appeared that the Ovatoscutum is pelagic Hydrozoa Chondrophora, which became popular and was widely quoted despite absence of additional researches and facts.^{[3][4][2][5][6]} As far back as 1966 Glaessner and Wade remarked that no evidence of a velellid 'sail' exists in Ovatoscutum and that Ovatoscutum differs from all Porpitidae chondrophora.^[1]

Ovatoscutum fossils are negative imprints on the bases of sandstone beds with the "elephant skin" and tubercle texture diagnostic of microbial mats. The same bedding planes contain various other benthic organisms: Yorgia, Andiva, Dickinsonia, Tribrachidium, Kimberella, Parvancorina and others. The such Ediacara-type assemblages are having bedding-planes that preserve benthic organisms that appear not to have been transported in the course of their burial and they preserved in situ.^[7] This fact also does not support pelagic lifestyle and chondrophoran interpretation of the Ovatoscutum.

Mikhail A. Fedonkin places Ovatoscutum in the extinct bilaterian phylum Proarticulata.^[8][9]

See also

List of Ediacaran genera

References

1. ^ ^{a b c} Glaessner, M.F.; Wade, M. (1966). "The late Precambrian fossils from Ediacara, South Australia". Palaeontology 9 (4): 599. http://palaeontology.palass-pubs.org/pdf/Vol%209/Pages%20599-628.pdf. 
2. ^ ^{a b} Fedonkin, M.A. (1985). "Systematic Description of Vendian Metazoa". In Sokolov, B.S. and Iwanowski, A.B.. Vendian System: Historical–Geological and Paleontological Foundation, Vol. 1: Paleontology. Moscow: Nauka. pp. 70–106. 
3. ^ Waggoner, B.M. (1995). "Ediacaran Lichens: A Critique". Paleobiology 21 (3): 393–397. JSTOR 2401174. 
4. ^ Waggoner, B.; Collins, A.G. (2004). "Reductio Ad Absurdum: Testing The Evolutionary Relationships Of Ediacaran And Paleozoic Problematic Fossils Using Molecular Divergence Dates". Journal of Paleontology 78 (1): 51–61. doi:10.1666/0022-3360(2004)078<0051:RAATTE>2.0.CO;2. 
5. ^ Jenkins, R. J. F. (1992). "Functional and ecological aspects of Ediacarian assemblages". In Lipps, J., and Signor, P. W.. Origin and early evolution of the Metazoa. New York: Springer. pp. 131–176. ISBN 0306440679. OCLC 231467647. http://books.google.ru/books?id=gUQMKiJOj64C&pg=PA161&lpg=PA161. 
6. ^ Jensen, S.; Gehling, J.G.; Droser, M.L.; Grant, S.W.F. (2002). "A scratch circle origin for the medusoid fossil Kullingia". Lethaia 35 (4): 291–299. doi:10.1080/002411602320790616. http://earthsciences.ucr.edu/docs/Soren_scratch_2002.pdf. 
7. ^ Droser, M.; Gehling, J. & Jensen, S. (2006). "Assemblage palaeoecology of the Ediacara biota: The unabridged edition?". Palaeogeography, Palaeoclimatology, Palaeoecology 232: 131–147. doi:10.1016/j.palaeo.2005.12.015. http://www.earthscience.ucr.edu/people/droser/Droser_et_2006.pdf. 
8. ^ Fedonkin, M.A. (2002). "Andiva ivantsovi gen. et sp. n. and related carapace-bearing Ediacaran fossils from the Vendian of the Winter Coast, White Sea, Russia". Italian Journal of Zoology 69 (2): 175–181. doi:10.1080/11250000209356456. 
9. ^ Fedonkin, M.A. (2003). "The origin of the Metazoa in the light of the Proterozoic fossil record". Paleontological Research 7 (1): 35. doi:10.2517/prpsj.7.9. http://www.bionet.nsc.ru/live/ppt/Fedonkin_2003.pdf.