''Volborthella'' is an animal of uncertain classification, whose fossils pre-date . It has been considered for a period a cephalopod. However discoveries of more detailed fossils showed that ''Volborthella''’s small, conical shell was not secreted but built from grains of the mineral

silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...

(silica), and that it was not divided into a series of compartments by

septa SEPTA, the Southeastern Pennsylvania Transportation Authority, is a regional public transportation authority that operates bus, rapid transit, commuter rail, light rail, and electric trolleybus services for nearly four million people througho ...

as those of fossil shelled cephalopods and the living ''

Nautilus A nautilus (; ) is any of the various species within the cephalopod family Nautilidae. This is the sole extant family of the superfamily Nautilaceae and the suborder Nautilina. It comprises nine living species in two genera, the type genus, ty ...

'' are. This illusion was a result of the laminated texture of the organisms' tests. Therefore, ''Volborthella''’s classification is now uncertain. It has been speculated that it may in fact represent a

sclerite A sclerite (Greek language, Greek , ', meaning "hardness, hard") is a hardened body part. In various branches of biology the term is applied to various structures, but not as a rule to vertebrate anatomical features such as bones and teeth. Instea ...

of a larger organism, on the basis of one specimen; however, it may be premature to accept this hypothesis, as the arrangement of sclerites producing this impression may have occurred by chance. The Ordovician scleritome-bearing '' Curviconophorus'', as well as the Halwaxiids, lobopods and echinoderms, demonstrate the diversity of organisms which may produce a scleritome of this nature. The related ''Campitius'' was originally suggested to be part of a

radula The radula (; : radulae or radulas) is an anatomical structure used by mollusks for feeding, sometimes compared to a tongue. It is a minutely toothed, chitinous ribbon, which is typically used for scraping or cutting food before the food enters ...

rather than a scleritome, but is now considered a synonym of ''Volborthella''. ''Volborthella'' is widespread, and a useful biostratigraphic indicator; it has been found in

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Greenland Greenland is an autonomous territory in the Danish Realm, Kingdom of Denmark. It is by far the largest geographically of three constituent parts of the kingdom; the other two are metropolitan Denmark and the Faroe Islands. Citizens of Greenlan ...

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, and northeastern Europe, and is restricted to Lower Cambrian rocks, appearing before the trilobites and co-existing with them for some time. ''Volborthella'' has been described as a 'failed attempt in mineralisation'; it constructed its wall by agglutinating grains of sediment, much like some foramanifera, and declined in conjunction with the origin of truly- biomineralising organisms. However, its similarity to '' Salterella'', which contained embedded sediment grains in its mineralised wall, suggests a possible biological relationship - ''Salterella'' may have begun to mineralise its agglutinated wall. Some ''Volborthella'' specimens do show taphonomic hints that some form of lightly mineralised sheath may have enclosed its agglutinated shell.

References

{{Taxonbar, from1=Q18519633, from2=Q5150695 Enigmatic prehistoric animal genera Controversial taxa