''Stylonurella'' is a genus of prehistoric

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

. It is classified within the Parastylonuridae family and contains three species, ''S. arnoldi'' and ''S. beecheri'' from the

Devonian The Devonian ( ) is a period (geology), geologic period and system (stratigraphy), system of the Paleozoic era (geology), era during the Phanerozoic eon (geology), eon, spanning 60.3 million years from the end of the preceding Silurian per ...

Pennsylvania Pennsylvania, officially the Commonwealth of Pennsylvania, is a U.S. state, state spanning the Mid-Atlantic (United States), Mid-Atlantic, Northeastern United States, Northeastern, Appalachian, and Great Lakes region, Great Lakes regions o ...

United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...

and ''S. spinipes'' from the

Silurian The Silurian ( ) is a geologic period and system spanning 23.5 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 third and shortest period of t ...

of Kip Burn,

Scotland Scotland is a Countries of the United Kingdom, country that is part of the United Kingdom. It contains nearly one-third of the United Kingdom's land area, consisting of the northern part of the island of Great Britain and more than 790 adjac ...

.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 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 tortoises, the unde ...

. 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 (biology), 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 sy ...

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'' 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'', 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, and the second of twelve periods of the Phanerozoic Eon (geology), Eon. The Ordovician spans 41.6 million years f ...

), 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 st ...

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

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

), reclassified as a species of '' Kiaeropterus''.

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