''Stylonurella'' is a genus of prehistoric

eurypterid Eurypterids, often informally called sea scorpions, are a group of extinct arthropods that form the Order (biology), order Eurypterida. The earliest known eurypterids date to the Darriwilian stage of the Ordovician period 467.3 Myr, million yea ...

. It is classified within the

Parastylonuridae The Parastylonuridae are a family of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". The family is one of two families contained in the superfamily Stylonuroidea (along with Stylonuridae), which in tu ...

family and contains three species, ''S. arnoldi'' and ''S. beecheri'' from the

Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, whe ...

Pennsylvania Pennsylvania (; ( Pennsylvania Dutch: )), officially the Commonwealth of Pennsylvania, is a state spanning the Mid-Atlantic, Northeastern, Appalachian, and Great Lakes regions of the United States. It borders Delaware to its southeast, ...

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...

and ''S. spinipes'' from the

Silurian The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozo ...

of Kip Burn,

Scotland Scotland (, ) is a country that is part of the United Kingdom. Covering the northern third of the island of Great Britain, mainland Scotland has a border with England to the southeast and is otherwise surrounded by the Atlantic Ocean to the ...

.Dunlop, J. A., Penney, D. & Jekel, D. 2015. A summary list of fossil spiders and their relatives. In World Spider Catalog. Natural History Museum Bern, online at http://wsc.nmbe.ch, version 16.0 http://www.wsc.nmbe.ch/resources/fossils/Fossils16.0.pdf (PDF).

Description

''Stylonurella'' was a small stylonuroid, possessing a subquadrate

prosoma The cephalothorax, also called prosoma in some groups, is a tagma of various arthropods, comprising the head and the thorax fused together, as distinct from the abdomen behind. (The terms ''prosoma'' and ''opisthosoma'' are equivalent to ''cepha ...

with approximately the same length as width. The midsection was slightly constricted and the eyes were parallel and anteriorly located in the anterior half of the

carapace A carapace is a Dorsum (biology), 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 tor ...

. The metastoma and first two appendages are unknown, the third and fourth prosomal legs are very short and the last two walking legs are very long. The

metasoma The metasoma is the posterior part of the body, or tagma, of arthropods whose body is composed of three parts, the other two being the prosoma and the mesosoma. In insects, it contains most of the digestive tract, respiratory system, and circula ...

is very narrow. A revision of the families and genera of the Stylonuracea (Eurypterida)

Classification

Though one of the earliest described stylonurines, described shortly after the description of ''

Stylonurus ''Stylonurus'' is a genus of prehistoric eurypterid of the family Stylonuridae. The genus contains three species: ''Stylonurus powriensis'' from the Devonian of Scotland, ''Stylonurus shaffneri'' from the Devonian of Pennsylvania and ''Stylonurus ...

'' itself, it has no close relations to that genus. Indeed, there are numerous and apparent differences. For instance, the eyes of ''Stylonurus'' are located on the posterior half of the carapace and those of ''Stylonurella'' are on the anterior half. Furthermore, there are noticeable differences between ''Stylonurella'' and its closest relative, ''

Parastylonurus ''Parastylonurus'' is a genus of prehistoric eurypterid. It is classified within the Parastylonuridae family and contains three species, ''P. hendersoni'' and ''P. ornatus'' from the Silurian of Scotland and ''P. sigmoidalis'' from the Silurian ...

'', for instance the widely different shapes of the carapaces (quadrate in ''Stylonurella'' and subrounded in ''Parastylonurus'').

Species

''Stylonurella'' contains three valid species, with other named species now seen as invalid or as part of other genera. * ''Stylonurella''? ''arnoldi'' Ehlers, 1935 - Pennsylvania, USA (

) * ''Stylonurella''? ''beecheri'' Hall, 1884 - Pennsylvania, USA (

) * ''Stylonurella spinipes'' Page, 1859 - Kip Burn, Scotland (

) Invalid or reassigned species are listed below: * ''"Stylonurella" logani'' Woodward, 1872 - Kip Burn, Scotland (

), synonym of ''S. spinipes''. * ''"Stylonurella" modestus'' Clarke & Ruedemann, 1912 - New York, USA (

Ordovician The Ordovician ( ) is a geologic period and System (geology), system, the second of six periods of the Paleozoic Era (geology), Era. The Ordovician spans 41.6 million years from the end of the Cambrian Period million years ago (Mya) to the start ...

), 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 ...

. * ''"Stylonurella" otisius'' Clarke, 1907 - Eastern USA (

), reclassified as a species of '' Clarkeipterus''. * ''"Stylonurella" ruedemanni'' Størmer, 1934 - Ringerike, Norway (

), reclassified as a species of ''

Kiaeropterus ''Kiaeropterus'' is a genus of prehistoric eurypterid classified as part of the Rhenopteridae family. Two species, both from the Silurian period, are known; ''K. cyclophthalmus'' from Scotland and ''K. ruedemanni'' from Norway.Dunlop, J. A., P ...

''.

References

{{Taxonbar, from=Q7629699 Stylonuroidea Silurian arthropods of Europe Silurian eurypterids Eurypterids of Europe Devonian eurypterids Eurypterids of North America

Description

Classification

Species

See also

References