11 marzo 2012

Scoperto fossile con scheletro vissuto 560 milioni di anni fa

Coronacollina acula Un gruppo di paleontologi ha scoperto un fossile - denominato Coronacollina acula - vissuto tra 560 milioni e 550 milioni di anni fa, nel periodo Ediacarano. Finora non era stata rinvenuta traccia di scheletri prima del Cambriano (da 542 a 488 milioni di anni fa). Per questo scoperta del più antico animale dotato di parti dure introduce elementi di novità assai rilevanti.
La Coronacollina Acula non era in grado di muoversi e probabilmente viveva in colonie ancorate sul fondale marino. Il corpo dell'animale, di forma tronco conica e alto da 3 a 5 centimetri, era dotato di quattro sostegni aghiformi lunghi fino a 40 centimetri.
Andrea Mameli www.linguaggiomacchina.it 11 marzo 2012

The advent of hard-part structural support among the Ediacara biota: Ediacaran harbinger of a Cambrian mode of body construction
Erica C. Clites (Department of Earth Sciences, University of California)
Mary L. Droser (Department of Earth Sciences, University of California)
James G. Gehling (South Australian Museum, North Terrace, Adelaide)
Geology (Geological Society of America) Feb. 14, 2012
Abstract
Coronacollina acula The apparent lack of taxonomic continuity between the Precambrian and Cambrian fossil records has led to controversial and conflicting interpretations about the Ediacara biota and their place in the evolution of metazoan life on this planet. This has been further complicated by the absence of similar modes of construction between these faunas and the rarity of Precambrian skeletonized fossils. We describe a new Ediacaran organism that represents the oldest multielement organism with structural support through either biomineralization or chitin. Coronacollina acula gen. et sp. nov. from the Ediacara Member (Rawnsley Quartzite) was constructed from a framework of rigid and brittle elements that disarticulated after death. It reveals a constructional mode not recognized previously among members of this assemblage, but one that was prevalent among Cambrian organisms. Coronacollina consists of a truncated cone associated with spicules, up to 37 cm in length, diverging radially from the cone. This constructional morphology is similar to the Cambrian Choia, a low conical demosponge with a corona of long spicules, providing a long-predicted constructional link between the Ediacara biota and the Cambrian fossil record.

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