| Archaeaspinus Temporal range: | |
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| Archaeaspinus fedonkini | |
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| Genus: | Archaeaspinus Ivantsov, 2007 |
| Species: | A. fedonkiniIvantsov, 2001 |
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Archaeaspinus fedonkini is an extinct proarticulatan organism from the Late Precambrian (Ediacaran) period.
Archaeaspinus was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001. [1] 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. [2]
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. [3] [1] [4] The type species, A. fedonkini is the only species known in this genus. It appears in the fossil record between 571-551Ma. [5]
As with other genera within the family Yorgiidae, Archaeaspinus is discoid. Much of its body segmented by up to 15 bilateral isomers. [2] 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. [6] This lobe, or perhaps irregular isomer, is bordered by a shallow furrow on the anterior and left edge. [3]
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. [7]
It closely resembles Yorgia , because of the similar anterior region, and to a lesser extent Dickinsonia and other Proarticulates. [8]
Archaeaspinus belongs to the phylum Proarticulata. Within that, its class is Cephalozoa and family Yorgiidae. [9] [10] Until 2004 Cephalozoans were categorized within the class Vendiamorpha, so older records of the Archaeaspinus may label it a Vendiamorph. [11]
Newer analyses suggest that tissue on the ventral side of most Proarticulates, and therefore Archaeaspinus, bore cilia for feeding. [8]
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 did. [12]
Dickinsonia is a genus of extinct organism that lived during the late Ediacaran period in what is now Australia, China, Russia and Ukraine, most likely a basal animal. It is one of the best known members of the Ediacaran biota. The individual Dickinsonia typically resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; its mode of growth has been considered consistent with a stem-group bilaterian affinity, though various other affinities have been proposed. The discovery of cholesterol molecules in fossils of Dickinsonia lends support to the idea that Dickinsonia was an animal, though these results have been questioned.
Tribrachidium heraldicum is a tri-radially symmetric fossil animal that lived in the late Ediacaran (Vendian) seas. In life, it was hemispherical in form. T. heraldicum is the best known member of the extinct group Trilobozoa.
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 25 cm (9.8 in). It is classified within the extinct animal phylum Proarticulata.
Cephalonega stepanovi is a fossil organism from Ediacaran deposits of the Arkhangelsk Region, Russia. It was described by Mikhail A. Fedonkin in 1976
Vendia is a genus of oval-shaped, Ediacaran fossils ranging from 4.5 to 12.5 mm long. The body is completely segmented into isomers, which are arranged alternately in two rows longitudinal to the axis of the body. The larger isomers cover the smaller ones externally but the posterior ends of all the isomers remain free. The transverse elements decrease in size from anterior to posterior and are all inclined in the same direction.
Trilobozoa is a phylum of extinct, sessile animals that were originally classified into the Cnidaria. The basic body plan of trilobozoans is often a tri-radial or radial sphere-shaped form with lobes radiating from its centre. Fossils of trilobozoans are restricted to marine strata of the Late Ediacaran period.
Praecambridium sigillum is an extinct organism that superficially resembles a segmented trilobite-like arthropod. It was originally described as being a trilobite-like arthropod, though the majority of experts now place it within the Proarticulata as a close relative of the much larger Yorgia. It is from the Late Ediacaran deposit of Ediacara Hills, Australia, about 555 million years ago. On average, P. sigillum had at least 5 pairs of segments, with each unit becoming progressively larger as they approach the cephalon-like head.
Anfesta stankovskii is a tri-radially symmetrical fossil animal that lived in the late Ediacaran (Vendian) seafloor. It is a member of the extinct group Trilobozoa.
Proarticulata is a proposed phylum of extinct, bilaterally symmetrical animals known from fossils found in the Ediacaran (Vendian) marine deposits, and dates to approximately 567 to 550 million years ago. The name comes from the Greek προ = "before" and Articulata, i.e. prior to animals with true segmentation such as annelids and arthropods. This phylum was established by Mikhail A. Fedonkin in 1985 for such animals as Dickinsonia, Vendia, Cephalonega, Praecambridium and currently many other Proarticulata are described.
Vendiamorpha is a class of extinct animals within the Ediacaran phylum Proarticulata.
Isomer is an element of transverse body articulation of the bilateral fossil animals of the Phylum Proarticulata from the Ediacaran (Vendian) period. This term has been proposed by Andrey Yu. Ivantsov, a Russian paleontologist from the Laboratory of the Precambrian organisms, Paleontological Institute, Russian Academy of Sciences.
Epibaion is a trace fossil imprint of the Ediacaran animals of the phylum Proarticulata, which became extinct in the Precambrian. Imprints often occurring in chains, that is interpreted as a feeding trace; some chains terminate in a body fossil, allowing their maker to be identified. Several specimens are known; E. waggoneris was produced by Yorgia waggoneri; E. costatus by Dickinsonia costata, and E. axiferus, the type species, has as yet not been found with a trace-maker. It is proposed that the Australian fossil Phyllozoon is also a feeding trace of Proarticulata.
Protechiurus edmondsi is a species of fossil animal from the Ediacaran Nama group of Namibia. It was initially interpreted as an echiurid worm. It has been placed as a "vendobiont", on the hypothesis that the Edicarian fauna represent a distinct phylum. It has also been suggested that it may be an ecdysozoan.
Andiva ivantsovi is a Vendian fossil, identified to be a bilaterian triploblastic animal in the Ediacaran phylum Proarticulata, known from the Winter Coast, White Sea, Russia. It was first discovered in 1977, and described as a new species in a new genus by Mikhail Fedonkin in 2002. It lived about 555 million years ago. Fossils of Andiva also occur in South Australia. All known fossils of Andiva are external molds.
The petalonamids (Petalonamae) are an extinct group of archaic animals typical of the Ediacaran biota, also called frondomorphs, dating from approximately 635 million years ago to 516 million years ago. They are benthic and motionless animals, that have the shape of leaves, fronds (frondomorphic), feathers or spindles and were initially considered algae, octocorals or sea pens. It is now believed that there are no living descendants of the group, which shares a probable relation to the Ediacaran animals known as Vendozoans.
Armillifera parva is a species of Ediacaran proarticulate first described by Mikhail Fedonkin in 1980. Its fossils were discovered in the White Sea area, Arkhangelsk Region, Russia. These fossils of A. parva were restricted to almost the same stratigraphic range as Kimberella, although fossils of both organisms have been rarely found.
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.
Yorgiidae is an extinct family of cephalozoans, which lived 635 million years ago. They were filter fed.
Ivovicia is an extinct genus of proarticulates. This monotypic genus has only one species: Ivovicia rugulosa.The genus is named after the Ivovik creek, near the place where the specimen was found.
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