''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 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, known from the Winter 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 ...

by Mikhail Fedonkin 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, 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 ...

Proarticulata. The original reconstruction by Fedonkin proposed that the ridged surface was a convex, thin carapace 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'', '' Yorgia'', '' Kimberella'', '' Brachina'', '' Parvancorina'', ''

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

Proarticulata. '' Archaeaspinus'' and '' Cyanorus'' have also been directly compared to it. Jerzy Dzik includes ''Andiva'' in the Dipleurozoa, with ''Chondroplon'' as the closest relative, separated from ''Dickinsonia'' and closer to ''Yorgia'', '' Praecambridium'', ''Archaeaspinus'' and '' Vendia'', 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