''Parvancorina'' is a

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 ...

of shield-shaped bilaterally symmetrical

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 ...

animal that lived in 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 ...

seafloor. It has some superficial similarities with the

Cambrian The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordov ...

trilobite-like

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

Etymology

The generic name is derived from a crasis

compound word In linguistics, a compound is a lexeme (less precisely, a word or Sign language, sign) that consists of more than one Word stem, stem. Compounding, composition or nominal composition is the process of word formation that creates compound lexemes. C ...

from the Latin ''parva ancora'' (small anchor). The specific name of the type species, ''P. minchami'', honors Mr. H. Mincham, the private collector, who in 1957 had collected and presented a number of fine specimens of Ediacaran fossils to the South Australian Museum. The specific name of ''P. sagitta'' is the Latin word ''sagitta'' (arrow), in direct reference to the arrow-like shape.

Occurrence

''P. minchami'' fossils were first discovered in the Ediacara Member of the Rawnslay Quartzite, Flinders Ranges, 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 ...

. This species is also known from deposits of the Verkhovka, Zimnegory and Yorga Formations in 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 ...

area of the Arkhangelsk Region,

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 ...

. Additionally, similar poorly preserved ''Parvancorina'' sp. fossils were found in the Lyamtsa Formation of this Russian region. This Species is also recorded from Sursager area in Jodhpur region, Sonia Formation of Marwar Supergroup in India. ''P. sagitta'' is found in the Verkhovka formation on the Solza River, White Sea area of the Arkhangelsk Region, Russia. Parvancorina

Description

It has a raised ridge down the central axis of symmetry. This ridge can be high in unflattened

s. At the 'head' end of the ridge there are two quarter-circle-shaped raised arcs attached. In front of this are two nested semicircular lines. The fossils are normally about in each of width and length, but can be up to .

Affinity

In attempting to determine its phylogenic relationships, ''Parvancorina'' has been compared with trilobite-like arthropods, such as '' Skania'' from the Burgess Shale Biota,

Canada Canada is a country in North America. Its Provinces and territories of Canada, ten provinces and three territories extend from the Atlantic Ocean to the Pacific Ocean and northward into the Arctic Ocean, making it the world's List of coun ...

, and '' Primicaris'' from the Chengjiang Biota,

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

. However, the growth form of ''Parvancorina'' is unusual for an arthropod. Furthermore, the strong resemblance of ''P. sagitta'' to the primitive mollusk-like bilateran '' Temnoxa'' and similarities to parts of '' Kimberella'' casts further doubt on an arthropod affinity.

Lifestyle and habitus

''Parvancorina'' typically lived with their "heads" parallel to the current direction. Overfolding of the fossils from all sides contradicts any form of stalked attachment to the sea floor. They are suggested to have been mobile and able to actively orientate their bodies towards the current direction, with smaller individuals from the Ediacara biota in Australia often found in close association with each other. They have been proposed to be filter feeders, using their body ridges to direct water towards feeding structures, with deposit feeding being a possible but less likely ecology.

References

External links

Ediacaran.orgHome of the Ediacaran
* {{Taxonbar, from=Q763329 Ediacaran life Enigmatic prehistoric animal genera White Sea fossils Fossil taxa described in 1958