''Archaeaspinus fedonkini'' is an extinct
proarticulata
Proarticulata is a proposed phylum of extinct, near-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. ...
n organism from the Late
Ediacaran
The Ediacaran ( ) is a geological period of the Neoproterozoic geologic era, Era that spans 96 million years from the end of the Cryogenian Period at 635 Million years ago, Mya to the beginning of the Cambrian Period at 538.8 Mya. It is the last ...
period.
Background
''Archaeaspinus'' was discovered in
Zimnii Bereg, the
Winter Coast
The Winter Coast (''Zimniy Bereg'', ) is a coastal area in Arkhangelsk Oblast in northwest Russia. It is located on the eastern side of the Dvina Bay in the White Sea, between the Northern Dvina delta and Cape Voronov, opposite to the Summer Coast ...
of the
White Sea
The White Sea (; Karelian language, Karelian and ; ) is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is surrounded by Karelia to the west, the Kola Peninsula to the north, and the Kanin Peninsula to the nort ...
in
Russia
Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
, 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
The Flinders Ranges are the largest mountain ranges in South Australia, which starts about north of Adelaide. The ranges stretch for over from Port Pirie to Lake Callabonna.
The Adnyamathanha people are the Aboriginal group who have inhab ...
in
South Australia
South Australia (commonly abbreviated as SA) is a States and territories of Australia, state in the southern central part of Australia. With a total land area of , it is the fourth-largest of Australia's states and territories by area, which in ...
as well.
Originally called ''
Archaeaspis''—a name already applied to 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 in this genus. It appears in the fossil record between 571-551Ma.
Description
As with other genera within the family
Yorgiidae
Yorgiidae is an extinct family of the class Cephalozoa, which is a part of the wider phylum Proarticulata. They lived from around 571 to 551 Ma.
Description
Like other relatives within the phylum Proarticulata, their body plan consists of is ...
, ''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 the isomer that is furthest forward 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 Proart ...
'', because of the similar anterior region, and to a lesser extent ''
Dickinsonia
''Dickinsonia'' is a genus of extinct organism that lived during the late Ediacaran period in what is now Australia, China, Russia, and Ukraine. It had a round, bilaterally symmetric body with multiple segments running along it. It could range f ...
'' and other
Proarticulates.
Phylogenetic relationships
''Archaeaspinus'' belongs to the phylum
Proarticulata
Proarticulata is a proposed phylum of extinct, near-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. ...
. Within that, its class is
Cephalozoa
Cephalozoa are an extinct class (biology), class of primitive segmented marine organisms within the Phylum (biology), Phylum Proarticulata from the Ediacaran period. They possessed bilateral symmetry and were characterized by a thin, rounded body ...
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 r ...
, 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 or filter-feeding strategy, absorbing nutrients from the microbial mat below in much the same way that ''
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 Proart ...
'' did.
References
{{Taxonbar, from1=Q114835855, from2=Q107144612
Proarticulata
Yorgiidae