''Andiva ivantsovi'' is a

Vendian 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 ...

fossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserve ...

, identified to be a

bilaterian Bilateria () is a large clade of animals characterised by bilateral symmetry during embryonic development. This means their body plans are laid around a longitudinal axis with a front (or "head") and a rear (or "tail") end, as well as a left–r ...

triploblastic Triploblasty is a condition of the gastrula in which there are three primary germ layers: the ectoderm, mesoderm, and endoderm. Germ cells are set aside in the embryo at the blastula stage, and are incorporated into the gonads during organogenesis ...

animal in the

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 ...

phylum In biology, a phylum (; : phyla) is a level of classification, or taxonomic rank, that is below Kingdom (biology), kingdom and above Class (biology), class. Traditionally, in botany the term division (taxonomy), division has been used instead ...

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. ...

, known from 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 ...

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 ...

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 ...

. It was first discovered in 1977, and described as a new species in a new

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Mikhail Fedonkin Academician Mikhail Aleksandrovich Fedonkin (; born June 19, 1946) is a Russian paleontologist specializing in documentation of the earliest animals' body fossils, tracks, and trails. He has also described numerous Vendian-aged fossils includin ...

in 2002. It lived about 555 million years ago. Fossils of ''Andiva'' also occur 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 ...

. All known fossils of ''Andiva'' are external molds.

Description

''Andiva'' was between long and from wide, with a bilaterally symmetrical shape, larger on the anterior end and narrower at the posterior. The anterior part features a smooth "fringe" followed by a surface "covered by fine ribs and sutura", also described as a "quilt" with narrow, tightly packed chambers The symmetry of these ribs is a

glide symmetry In geometry, a glide reflection or transflection is a geometric transformation that consists of a reflection across a hyperplane and a translation ("glide") in a direction parallel to that hyperplane, combined into a single transformation. Bec ...

, that is, in which the corresponding segments on the left and right sides do not line up, but are staggered. This is a feature shared by other forms belonging to the proposed

taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...

. The original reconstruction by Fedonkin proposed that the ridged surface was a convex, thin

carapace A carapace is a dorsal (upper) 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 unde ...

made of a chitin-like, non mineralized substance, protecting the animal while "creeping or gliding" over the sea bed. In the same reconstruction, the smooth zone was considered an imprint of the soft tissue beneath the dorsal carapace.

Association

''Andiva'' is often found together with other species from the Ediacara biota, like ''

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 ...

'', ''

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 ...

'', ''

Kimberella ''Kimberella'' is an extinct genus of marine bilaterian known only from rocks of the Ediacaran period. The slug-like organism fed by scratching the microbial surface on which it dwelt in a manner similar to the gastropods, although its affinity ...

'', '' Brachina'', ''

Parvancorina ''Parvancorina'' is a genus of shield-shaped bilaterally symmetrical fossil animal that lived in the late Ediacaran seafloor. It has some superficial similarities with the Cambrian trilobite-like arthropods. Etymology The generic name is deriv ...

'', ''

Tribrachidium ''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. Etymolo ...

'' and others.

Taxonomy and relationships

Morphologically, ''Andiva'' most closely resembles ''

Ovatoscutum ''Ovatoscutum concentricum'' is one of many enigmatic organisms known from the Ediacaran deposits of the Flinders Ranges, Australia, and the White Sea area in Russia, dating around 555 Ma. Etymology The generic name ''Ovatoscutum'' is derived fr ...

'', ''

Chondroplon ''Chondroplon bilobatum'' is a medusoid Ediacaran fossil. It has sand-filled tubes, although these may not have been sand-filled in life. It has a shield-like shape, with one end different from the other, and bilateral symmetry, and although it ...

'' and, more distantly, ''Dickinsonia'', as part of the proposed

. ''

Archaeaspinus ''Archaeaspinus fedonkini'' is an extinct proarticulatan organism from the Late Ediacaran period. Background ''Archaeaspinus'' was discovered in Zimnii Bereg, the Winter Coast of the White Sea in Russia, by A. Yu. Ivantsov in 2001. Since the ...

'' and ''

Cyanorus ''Cyanorus singularis'' is a small proarticulatan, closely related to ''Spriggina'' and ''Marywadea''. The anterior part of the body was most likely not segmented. The axial structure of it combines features of the ''Vendia'' species and ''Dickin ...

'' have also been directly compared to it. Jerzy Dzik includes ''Andiva'' in the

Dipleurozoa Dipleurozoa (or Dickinsoniomorpha) are extinct proarticulate organisms of the Ediacaran period, which had a flat and more or less ovoid shape. Polychaete worms were treated, however it seems more likely that they were vendobionts. The most re ...

, with ''Chondroplon'' as the closest relative, separated from ''Dickinsonia'' and closer to ''Yorgia'', ''

Praecambridium ''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 Proartic ...

'', ''Archaeaspinus'' and ''

Vendia ''Vendia'' is an extinct vendiamorph from the late Ediacaran, estimated to be around 567 - 550 Ma years old, it contains two species, ''V. sokolovi'' and ''V. rachiata'', both of which are restricted to the Ust' Pinega Formation in Northwestern ...

'', since all of them are sharing a dextrally bent dorsal medial chamber.

References

{{Taxonbar, from=Q4754504 Cephalozoa Prehistoric bilaterian genera Monotypic prehistoric animal genera Fossil taxa described in 2002 White Sea fossils Ediacaran life Fossils of Russia

Description

Association

Taxonomy and relationships

See also

References