''Archaeaspinus fedonkini'' is an extinct

proarticulata Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately . The name comes from the Greek () = "before" and Articulata, i.e. pr ...

n organism from the Late Precambrian (

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 th ...

) period.

Background

''Archaeaspinus'' was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001. Since then, numerous additional fossils have been attributed to the genus, mostly from that same type locality, but a small number from Flinders Ranges in South Australia as well.Mikhail A. Fodonkin, James G. Gehling, Kathleen Grey, Guy M. Narbonne, Patricia Vickers-Rich
''The Rise of Animals, Evolution and Diversification of the Kingdom Animalia''
Johns Hopkins University Press, Baltimore, 2007 Originally called ''

Archaeaspis ''Archaeaspis'' is an extinct genus of redlichiid trilobites. It lived during the late Atdabanian stage, which lasted from 521 to 515 million years ago during the early part of the Cambrian Period. The first specimens were first found in Siberi ...

''—a name already preoccupied by a redlichiid trilobite—in 2001 by Ivantsov, it was later recombined under its current name in 2007 by the same author. The type species ''A. fedonkini'' is the only species known to the genus. It appears in the fossil record between 571-551Ma. Photo_of_

Description

Like other genera within the family Yorgiidae, ''Archaeaspinus'' is discoid, much of its body segmented by up to 15 bilateral isomers. It has an unsegmented anterior end reminiscent of a head, full of what may be distribution channels. It also contains what appears to be an unpaired lobe which branches off of the foreword-most isomer to loop within the "head" section, following the shape of the body. This lobe, or perhaps irregular isomer, is bordered by a shallow furrow on the anterior and left edge. The isomers are arranged in a gliding reflection symmetry, thought to have increased in size and quantity as the organism aged and grew. The dorsal side is covered with evenly spaced tubercles. Though originally thought to have been soft bodied, it has also been suggested that ''Archaeaspinus'' had a delicate, flexible carapace ("cover tissue") covering its dorsal side. It closely resembles ''

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 ...

'', because of the similar anterior region, and to a lesser extent ''

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 ...

'' and other Proarticulates.

Phylogenetic relationships

As noted above, ''Archaeaspinus'' belongs to the phylum

Proarticulata Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately . The name comes from the Greek () = "before" and Articulata, i.e. pr ...

. Within that, its class is

Cephalozoa Cephalozoa are an extinct class of primitive segmented marine organisms within the Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body. Description Unlike the other cl ...

and family Yorgiidae. Until 2004 Cephalozoans were categorized within the class

Vendiamorpha Vendiamorpha is a class of extinct animals within the Ediacaran phylum Proarticulata. The typical vendiamorph had an oval-shaped or round-shaped body divided completely into segmented isomers, that were arranged alternately in two rows with ...

, so older records of the ''Archaeaspinus'' may label it a Vendiamorph. Newer analyses suggest that tissue on the ventral side of most Proarticulates, and therefore ''Archaeaspinus,'' bore cilia for feeding.

Paleoecology

''Archaeaspinus'' is thought to have used an

osmotrophic Osmotrophy is a feeding mechanism involving the movement of dissolved organic compounds by osmosis for nutrition. Organisms that use osmotrophy are called osmotrophs. Some mixotrophic microorganisms use osmotrophy to derive some of their energy. ...

or filter-feeding strategy, absorbing nutrients from the microbial mat below in much the same way that ''

'' did.

References

{{Taxonbar, from=Q107144612 Proarticulata Yorgiidae