Stylonuridae are an extinct family of prehistoric eurypterid

Eurypterid

Eurypterids are an extinct group of arthropods related to arachnids which include the largest known arthropods that ever lived. They are members of the extinct order Eurypterida ; which is the most diverse Paleozoic chelicerate order in terms of species...

s within the Superfamily Stylonuroidea

Stylonuroidea

Stylonuroidea are an extinct superfamily of eurypterids. They were members of the subphylum Chelicerata.-Description:Stylonuroidea, which lived from the Ordovician to Lower Permian periods, were characterized by their last pair of prosomal appendages, which were developed as walking legs, or less...

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Description

Stylonuridae, which lived from the Ordovician

Ordovician

The Ordovician is a geologic period and system, the second of six of the Paleozoic Era, and covers the time between 488.3±1.7 to 443.7±1.5 million years ago . It follows the Cambrian Period and is followed by the Silurian Period...

 to Lower Permian

Permian

The PermianThe term "Permian" was introduced into geology in 1841 by Sir Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil; Murchison asserted in 1841 that he named his "Permian...

 periods, 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.

Genera

• Class Merostomata
  Merostomata
  Merostomata is the name given to a grouping of the extinct Eurypterida and the Xiphosura . The term was originally used by James Dwight Dana to refer to Xiphosura only, but was emended by Henry Woodward to cover both groups....
  
   Dana, 1852
• Order Eurypterida Burmeister, 1843
• Superfamily Stylonuroidea
  Stylonuroidea
  Stylonuroidea are an extinct superfamily of eurypterids. They were members of the subphylum Chelicerata.-Description:Stylonuroidea, which lived from the Ordovician to Lower Permian periods, were characterized by their last pair of prosomal appendages, which were developed as walking legs, or less...
  
   Diener, 1924

  Family Stylonuridae Diener, 1924

  Genus Stylonurus

  Stylonurus

  Stylonurus is a genus of prehistoric eurypterid of the Family Stylonuridae.-Description:Stylonurids, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited variable shape, with arcuate...

  
  Page, 1856

  Genus Drepanopterus

  Drepanopterus

  Drepanopterus is an extinct genus of eurypterid. There are currently two species assigned to the genus. The genus has in the past been assigned its own family, with nine species associated with the genus Drepanopterus, however five of these have since been proven to be synonyms of pre-existing...

  
  Laurie, 1892

  Genus Brachyopterus

  Brachyopterus

  Brachyopterus is a genus of prehistoric eurypterid of the family Rhenopteridae.-Description:Brachyopterus is distinguished by its small size, compound eyes with axes converging anteriorly on a subtrapezoid to subpentagonal prosoma...

  
  Størmer, 1951

  Genus Ctenopterus

  Ctenopterus

  Ctenopterus is a genus of prehistoric eurypterid of the Family Stylonuridae. It contains only one species.-Description:Stylonurids, which lived from the Ordovician to Lower Permian periods, were small to very large forms with scales developing into tubercules and knobs. The prosoma exhibited...

  
  Clarke & Ruedemann, 1912

  Genus Tarsopterella

  Tarsopterella

  Tarsopterella is a genus of prehistoric eurypterid of the Family Hardieopteridae. It contains only one species.-Description:Tarsopterella is distinguished by its prosoma , which is subrectangular and slightly concave in front, with small compound eyes. Its abdomen has pronounced lateral epimera...

  
  Størmer, 1951

  Genus Melbournopterus

  Melbournopterus

  Melbournopterus is a genus of prehistoric chelicerate, known from the Upper Silurian of Australia. It is of uncertain taxonomic placement within the subphylum Chelicerata.-Description:...

  
  Caster & Kjellesvig-Waering, 1953

  Genus Campylocephalus

  Campylocephalus

  Campylocephalus is a genus of prehistoric eurypterid of the Family Hibbertopteridae.-Description:Campylocephalus is distinguished by its prosoma , which is subsemicircular and strongly convex, with subcentral compound eyes separated by inflated lobes. Its abdominal tergites are convex, with...

  
  Eichwald, 1860