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Kingdom  Animalia
Class  Merostomata
Family  †Pterygotidae
Rank  Genus
Subphylum  Chelicerata
Superfamily  †Pterygotioidea
Phylum  Arthropoda
Order  Eurypterid
Acutiramus FileAcutiramus cummingsijpg Wikimedia Commons
Similar  Eurypterid, Slimonia, Pterygotus, Hughmilleria, Eurypterus

Acutiramus is an extinct genus of eurypterid which lived in the Late Silurian (Ludlow) to Early Devonian.


Acutiramus is one of the largest eurypterids with pincers 5 cm and length about 2 m. The genus closely related to Pterygotus, of which several species were originally placed in, and to the giant Jaekelopterus.

Acutiramus Acutiramus Sea Scorpion On Black Digital Art by Jan Sovak


Acutiramus Pinterest The world39s catalog of ideas

Pterygotids, which lived from the Ordovician to Devonian periods, were characterized by small to large exoskeletons with semilunar scales. The telson, (tail) was expanded, or flatter than it was tall. Pterygotids also had chelicerae (claws in front of the mouth) that were large and long, with strong, well developed teeth on the claws. Their walking legs were small and slender, without spines.

Acutiramus Image Magnificent Rocks

Acutiramus is distinguishable from other pterygotids by the distal margin of the chelae, where the final tooth is at an acute angle to the rest of the claw (hence the name Acutiramus, or “acute arm”). The large tooth in the center of the claw is distally inclined, which is to say it points forwards. The prosoma (head) is subquadrate, with compound eyes located at the edge of the front corners. The telson has a low row of knobs running down its center.


Acutiramus httpsuploadwikimediaorgwikipediacommonsthu
  • Acutiramus Ruedemann, 1935
  • Acutiramus bohemicus (Barrande, 1872) — Silurian, Czech Republic
  • syn.= Pterygotus comes Barrande, 1872 — Silurian, Czech Republic
  • syn.= Pterygotus mediocris Barrande, 1872 — Silurian, Czech Republic
  • syn.= Pterygotus blahai Semper, 1898 — Silurian, Czech Republic
  • syn.= Pterygotus fissus Seemann, 1906 — Silurian, Czech Republic
  • Acutiramus cummingsi (Grote & Pitt, 1875) — Silurian USA & Canada
  • syn.= Pterygotus acuticaudatus Pohlman, 1882 — Silurian, USA
  • syn.= Pterygotus buffaloensis Pohlman, 1881 — Silurian, USA
  • syn.= Pterygotus quadraticaudatus Pohlman, 1882 — Silurian, USA
  • Acutiramus floweri Kjellesvig-Waering & Caster, 1955 — Silurian, USA
  • Acutiramus macrophthalmus (Hall, 1859) — Silurian USA & Canada
  • syn.= Pterygotus osborni Hall, 1859 — Silurian, USA
  • syn.= Pterygotus cobbi var. juvenis Clarke & Ruedemann, 1912 — Silurian, USA
  • Acutiramus perneri Chlupáč, 1994 — Devonian, Czech Republic
  • Acutiramus perryensis Leutze, 1958 — Silurian, USA
  • Acutiramus suwanneensis Kjellesvig-Waering, 1955 — Silurian?, USA

  • Acutiramus FileAcutiramus macrophthalmusJPG Wikimedia Commons
    Acutiramus Specimens


    Acutiramus Wikipedia

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