Stylonuridae is a family of

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 ...

s, an extinct group of

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

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

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 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 turn ...

), which in turn is one of four superfamilies classified as part of the suborder

Stylonurina Stylonurina is one of two suborders of eurypterids, a group of extinct arthropods commonly known as "sea scorpions". Members of the suborder are collectively and informally known as "stylonurine eurypterids" or "stylonurines". They are known from ...

. Stylonuridae, which lived from Early Silurian to the

Late Devonian The Devonian ( ) is a geologic period and system of the Paleozoic era during the Phanerozoic eon, spanning 60.3 million years from the end of the preceding Silurian period at million years ago ( Ma), to the beginning of the succeeding ...

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

Systematics and genera

The Stylonuridae is classified within the superfamily

within the

. It contains five genera in total and one recognised subfamily; the Laurieipterinae containing genera '' Laurieipterus'' 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'' Page, 1856 * '' Qujingopterus'' Ma, 2024 * Subfamily Laurieipterinae Kjellesvig-Waering, 1966 **'' Ctenopterus'' Clarke & Ruedermann, 1912 ** '' Laurieipterus'' Kjellesvig-Waering, 1966

References

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