'' Pseudorhizostomites howchini'' is a enigmatic member of the

Ediacaran Biota The Ediacaran (; formerly Vendian) biota is a Taxonomy (biology), taxonomic period classification that consists of all life forms that were present on Earth during the Ediacaran Period (). These were composed of enigmatic tubular and frond-sh ...

which was originally been thought to have been a

jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

of some kind (Sepkoski, 2002). ''P. howchini'' is now though to either have been a

pseudofossil Pseudofossils are inorganic objects, markings, or impressions that might be mistaken for fossils. Pseudofossils may be misleading, as some types of mineral deposits can mimic lifeforms by forming what appear to be highly detailed or organized str ...

, a gas escape structure or perhaps the result of a

rangeomorph The rangeomorphs are a form taxon of frondose Ediacaran Ediacaran biota, fossils that are united by a similarity to ''Rangea''. Some researchers, such as Pflug and Narbonne, suggest that a natural taxon Rangeomorpha may include all similar-look ...

holdfast being pulled by currents or, if any of these possibilities are not true, some other force from the sediments which enclosed the fossil.

Distribution and discovery

Reginald Sprigg Reginald Claude Sprigg, (1 March 1919 – 2 December 1994) was an Australian geologist and conservationist. At 17 he became the youngest Fellow of the Royal Society of South Australia. During 1946, in the Ediacara Hills, South Australia he di ...

found the

Holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

of ''P. howchini'' within the Flinders Ranges of

South Australia South Australia (commonly abbreviated as SA) is a state in the southern central part of Australia. It covers some of the most arid parts of the country. With a total land area of , it is the fourth-largest of Australia's states and territories ...

. Fossils of ''Pseudorhizostomites'' also occur within the

White Sea The White Sea (russian: Белое море, ''Béloye móre''; Karelian and fi, Vienanmeri, lit. Dvina Sea; yrk, Сэрако ямʼ, ''Serako yam'') is a southern inlet of the Barents Sea located on the northwest coast of Russia. It is su ...

region of Russia on Zimnii Bereg, the Dniester River Basin of

Podolia Podolia or Podilia ( uk, Поділля, Podillia, ; russian: Подолье, Podolye; ro, Podolia; pl, Podole; german: Podolien; be, Падолле, Padollie; lt, Podolė), is a historic region in Eastern Europe, located in the west-central ...

, Ukraine and Gornaya Baskkiria of the Ryauzyak Basin. These fossils are commonly found at all locations.

Classification and interpretations

Originally, Sepkoski (2002) suggested the possibility of the problematic fossils as being a

Jellyfish Jellyfish and sea jellies are the informal common names given to the medusa-phase of certain gelatinous members of the subphylum Medusozoa, a major part of the phylum Cnidaria. Jellyfish are mainly free-swimming marine animals with umbrella- ...

. Although a more modern and updated interpretation of ''P. howchini'' is it being a pseudo-fossil or a structure caused by the Holdfast of a

Petalonamid The petalonamids (Petalonamae) are an extinct group of archaic animals typical of the Ediacaran biota, also called frondomorphs, dating from approximately 635 million years ago to 516 million years ago. They are benthic and motionless animals, t ...

being pulled out by the currents. ''Pseudorhizostomites'' tends to occur around very thin impressions and casts of fossils which are the likely producer of ''Pseudorhizostomites'' if they decayed. The decayed parts of the organisms preserved alongside the biogenic structure were also interpreted as escaping through an overlying sand lamina. The species

Rugoconites tenuirugosus ''Rugoconites'' is a genus of Ediacaran biota found as fossils in the form of a circular or oval-like impression preserved in high relief, six or more centimeters in diameter. The fossils are surrounded by frills that have been interpreted ( Wad ...

was thought to be the originator behind ''P. howchini'' ; the fossil was also compared with the living Hydrozoan

Campanularia ''Campanularia'' is a genus of hydrozoans, in the family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is t ...

Description

''Pseudorhizostomites howchini'' is a form which represents a large amount of grooves radiating from a centre, which along the way irregularly branch out from one-another towards the outside. No distinct peripheral boundary is present in fossils. The central part which has the grooves radiating from is often strongly depressed (Negative hyporelief). The diameter of the grooves can often vary significantly, and can be from 9–60 mm in some specimens.

References

{{Reflist Ediacaran Ediacaran life Aquatic animals Enigmatic prehistoric animal genera Fossil taxa described in 1949

Distribution and discovery

Classification and interpretations

Description

See also

References