| 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.
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 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 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