Stylonuridae is a family of eurypterids, an extinct group of

chelicerate The subphylum Chelicerata (from New Latin, , ) constitutes one of the major subdivisions of the phylum Arthropoda. It contains the sea spiders, horseshoe crabs, and arachnids (including harvestmen, scorpions, spiders, solifuges, ticks, ...

arthropod Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a Segmentation (biology), segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and Arth ...

s commonly known as "sea scorpions". The family is one of two families contained in the superfamily

Stylonuroidea Stylonuroidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder Stylonurina. Stylonuroidea, which lived from ...

(along with Parastylonuridae), which in turn is one of four superfamilies classified as part of the suborder Stylonurina. Stylonuridae, which lived from Early Silurian to the

Late 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 ...

, were small to very large forms with scales developing into tubercules and knobs. The prosoma (head) exhibited variable shape, with arcuate compound eyes located subcentrally, or anteriorly. Their abdomens were slender. Their walking legs were long and powerful, sometimes characterized by spines. Most genera did not have swimming legs. 1955. Merostomata. ''Treatise on Invertebrate Paleontology, Part P Arthropoda 2, Chelicerata'', P: 36.

Description

Stylonurids are stylonuroids with undifferentiated opisthosoma with appendages II-IV being spiniferous akin to the genus '' Ctenopterus'', whilst appendages V-VI are non-spiniferous akin to the genus '' Pagea''. The fixed spines on appendages II-IV could have been used as dragnets to rake through the sediment, indiscriminately entangling anything within their sweeping arc. This type of sweep-feeding also occurs in the

Hibbertopteroidea Mycteropoidea is an extinct superfamily of eurypterids, an extinct group of chelicerate arthropods commonly known as "sea scorpions". It is one of four superfamilies classified as part of the suborder Stylonurina. Mycteropoids have been recovered ...

, though the adaptations of the hibbertopterids suggests they were more selective feeders.

Systematics and genera

The Stylonuridae is classified within the superfamily

within the Stylonurina. It contains five genera in total and one recognised subfamily; the Laurieipterinae containing genera ''

Laurieipterus ''Laurieipterus'' is a genus of a eurypterid classified as part of the family Stylonuridae. It contains one species, ''L. elegans'' from the Early Silurian of Scotland Scotland (, ) is a country that is part of the United Kingdom. Cover ...

'' and '' Ctenopterus''. "Laurieipterines" are diagnosed as stylonurids with broad metastoma and an epistoma with a rostral field and were restricted to the Early Silurian. Family Stylonuridae Diener, 1924 * '' Pagea'' Waterston, 1962 * ''

Soligorskopterus ''Soligorskopterus'' is a genus of eurypterid, a group of extinct aquatic arthropods. Fossils of ''Soligorskopterus'' have been discovered in deposits from the Late Devonian. The genus contains two species: ''S. tchepeliensis'', the type species ...

'' Plax ''et al.'', 2018 * ''

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 ...

'' Page, 1856 * Subfamily Laurieipterinae Kjellesvig-Waering, 1966 **'' Ctenopterus'' Clarke & Ruedermann, 1912 ** ''

'' Kjellesvig-Waering, 1966

References

Stylonuroidea Ordovician first appearances Cisuralian extinctions Prehistoric arthropod families {{Eurypterid-stub