Proarticulata is a proposed extinct phylum

Phylum

In biology, a phylum The term was coined by Georges Cuvier from Greek φῦλον phylon, "race, stock," related to φυλή phyle, "tribe, clan." is a taxonomic rank below kingdom and above class. "Phylum" is equivalent to the botanical term division....

 of very early bilateral

Bilateria

The bilateria are all animals having a bilateral symmetry, i.e. they have a front and a back end, as well as an upside and downside. Radially symmetrical animals like jellyfish have a topside and downside, but no front and back...

 animals known from fossils found in the Ediacaran

Ediacaran

The Ediacaran Period , named after the Ediacara Hills of South Australia, is the last geological period of the Neoproterozoic Era and of the Proterozoic Eon, immediately preceding the Cambrian Period, the first period of the Paleozoic Era and of the Phanerozoic Eon...

 (Vendian) fauna. Mikhail A. Fedonkin

Mikhail A. Fedonkin

Dr. Mikhail Aleksandrovich Fedonkin is an awarding winning paleontologist specializing in documentation of the earliest animals' body fossils, tracks, and trails. He was the first to describe several fossils including Hiemalora, Onega stepanovi, and Nimbia occlusa.Fedonkin is fluent in English and...

 describes animals in Proarticulata as having a "shield-like" shape, an unmineralized, thin, flexible carapace

Carapace

A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods such as crustaceans and arachnids, as well as vertebrates such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron.-Crustaceans:In crustaceans, the...

 and a thick, segmented

Segmentation (biology)

Segmentation in biology refers to either a type of gastrointestinal motility or the division of some animal and plant body plans into a series of repetitive segments. This article will focus on the segmentation of animal body plans, specifically using the examples of the phyla Arthropoda,...

 body. The segmentation is described as a "symmetry of gliding reflection

Glide reflection

In geometry, a glide reflection is a type of isometry of the Euclidean plane: the combination of a reflection in a line and a translation along that line. Reversing the order of combining gives the same result...

", in which the correspoding segments on the left and right sides do not line up, but are staggered. Fedonkin suggests that Proarticulata may be ancestral to the chordate

Chordate

Chordates are animals which are either vertebrates or one of several closely related invertebrates. They are united by having, for at least some period of their life cycle, a notochord, a hollow dorsal nerve cord, pharyngeal slits, an endostyle, and a post-anal tail...

s. Fedonkin places the genera

Genus

In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...

 Dickinsonia

Dickinsonia

Dickinsonia is an iconic fossil of the Ediacaran biota. It resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; most interpretations consider it to be an animal, although others suggest it may be fungal, or a member of an "extinct kingdom".-Species variety:A...

, Yorgia

Yorgia

Yorgia waggoneri is a member of the Ediacara biota, and resembles a cross between the organisms Dickinsonia and Spriggina. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of...

, Vendia

Vendia

Vendia is an oval-shaped, Ediacaran fossil from 4.5 to 12.5 mm long. Its 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...

, Archaeaspinus, Andiva and Ovatoscutum

Ovatoscutum

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....

in Proarticulata. A. Yu. Ivantsov has proposed that the genera Tamga

Tamga (fossil)

Tamga hamulifera is a disk-shaped fossil from Precambrian strata of the White Sea area, in Russia.-Description:The small , disk-shaped fossil has seven hook-like isomers in a star-like arrangement in the clearly expressed peripheral undivided zone. T...

, Lossinia, Ivovicia and Onega

Onega (fossil)

Onega stepanovi is one of the lesser known fossil taxa from the Ediacaran Period. It was described by Mikhail A. Fedonkin in 1976and was placed in the Phylum Proarticulata in 1985....

are in or close to Proarticulata.

Body fossils

• Armillifera Fedonkin, 1980

A. parva Fedonkin, 1980

• Andiva Fedonkin, 2002

A. ivantsovi Fedonkin, 2002

• Archaeaspinus Ivantsov, 2007 (=Archaeaspis Ivantsov, 2001)

A. fedonkini Ivantsov, 2001

• Chondroplon Wade, 1971 (possible =Dickinsonia)

C. bilobatum Wade, 1971

• Cyanorus Ivantsov, 2004

C. singularis Ivantsov, 2004

• Dickinsonia
  Dickinsonia
  Dickinsonia is an iconic fossil of the Ediacaran biota. It resembles a bilaterally symmetrical ribbed oval. Its affinities are presently unknown; most interpretations consider it to be an animal, although others suggest it may be fungal, or a member of an "extinct kingdom".-Species variety:A...
  
  Sprigg, 1947

D. costata Sprigg, 1947

D. lissa Wade, 1972

D. menneri Keller 1976 (=Vendomia menneri Keller 1976)

D. tenuis Glaessner et Wade, 1966

• Ivovicia Ivantsov, 2007

I. rugulosa Ivantsov, 2007

• Karakhtia Ivantsov, 2004

K. nessovi Ivantsov, 2004

• Lossinia Ivantsov, 2007

L. lissetskii Ivantsov, 2007

• Marywadea
  Marywadea
  Marywadea is a genus of Ediacaran biota shaped like an oval with a central ridge. It is a bilaterian organism as evidenced by its symmetry. The fossil has an asymmetrical first chamber of the quilt. It has transverse ridges away from the central axis that may be gonads. The head is shaped as a...
  
  Glaessner, 1976

M. ovata Glaessner et Wade, 1966

• Onega Fedonkin, 1976

O. stepanovi Fedonkin, 1976

• Ovatoscutum Glaessner et Wade, 1966

O. concentricum Glaessner et Wade, 1966

• Paravendia Ivantsov, 2004

P. janae Ivantsov, 2001 (=Vendia janae Ivantsov, 2001)

• Phyllozoon
  Phyllozoon
  Phyllozoon is an Ediacaran imprint that resembles a proarticulatan and has been interpreted as a feeding trace. It usually occurs in long chains of imprints formed, presumably, as the making organism moved....
  
  Jenkins et Gehling, 1978

P. hanseni Jenkins et Gehling, 1978

• Podolimirus Fedonkin, 1983

P. mirus Fedonkin, 1983

• Praecambridium Glaessner et Wade, 1966

P. siggilum Glaessner et Wade, 1966

• Spriggina
  Spriggina
  Fossils of Spriggina are known from the Ediacaran period, around . The segmented organism reached about 3 cm in length and may have been predatory...
  
  Glaessner, 1958

S. floundersi Glaessner, 1958

• Tamga Ivantsov, 2007

T. hamulifera Ivantsov, 2007

• Valdainia Fedonkin, 1983

V. plumosa Fedonkin, 1983

• Vendia
  Vendia
  Vendia is an oval-shaped, Ediacaran fossil from 4.5 to 12.5 mm long. Its 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...
  
  Keller, 1969

V. sokolovi Keller, 1969

V. rachiata Ivantsov, 2004

• Yorgia
  Yorgia
  Yorgia waggoneri is a member of the Ediacara biota, and resembles a cross between the organisms Dickinsonia and Spriggina. It has a low, segmented body consisting of a short wide "head", no appendages, and a long body region, reaching a maximum length of...
  
  Ivantsov, 1999

Y. waggoneri Ivantsov, 1999

Trace fossils

• Epibaion Ivantsov, 2002

E. axiferus Ivantsov, 2002.

E. waggoneris Ivantsov, 2011. This is a trace of Yorgia waggoneri

E. costatus Ivantsov, 2011. This is a trace of Dickinsonia costata

External links

• Database of Ediacaran Biota Advent of Complex Life