Acutiramus
Encyclopedia
Acutiramus is an extinct genus of eurypterid
which lived in the Late Silurian
(Ludlow) to Early Devonian.
Acutiramus was one of the largest eurypterids with pincers 5 cm and length about 2 m. It was related to another large eurypterid, Pterygotus
.
, 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. Pterygotidae
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 Pterygotidae
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.
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...
which lived in the Late Silurian
Silurian
The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...
(Ludlow) to Early Devonian.
Acutiramus was one of the largest eurypterids with pincers 5 cm and length about 2 m. It was related to another large eurypterid, Pterygotus
Pterygotus
Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...
.
Description
PterygotidaePterygotidae
Pterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea, and were the only eurypterids to have a truly worldwide distribution, and include the largest arthropods to have ever lived.-Description:...
, 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. Pterygotidae
Pterygotidae
Pterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea, and were the only eurypterids to have a truly worldwide distribution, and include the largest arthropods to have ever lived.-Description:...
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 Pterygotidae
Pterygotidae
Pterygotidae are an extinct family of eurypterids. They were members of the superfamily Pterygotioidea, and were the only eurypterids to have a truly worldwide distribution, and include the largest arthropods to have ever lived.-Description:...
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.
Species
- Acutiramus Ruedemann, 1935
- Acutiramus bohemicus (Barrande, 1872) — Silurian, Czech Republic
- = Pterygotus comes Barrande, 1872 — Silurian, Czech Republic
- = Pterygotus mediocris Barrande, 1872 — Silurian, Czech Republic
- = Pterygotus blahai Semper, 1898 — Silurian, Czech Republic
- = Pterygotus fissus Seemann, 1906 — Silurian, Czech Republic
- Acutiramus cummingsi (Grote & Pitt, 1875) — Silurian USA & Canada
- = Pterygotus acuticaudatus Pohlman, 1882 — Silurian, USA
- = Pterygotus buffaloensis Pohlman, 1881 — Silurian, USA
- = Pterygotus quadraticaudatus Pohlman, 1882 — Silurian, USA
- Acutiramus floweri Kjellesvig-Waering & Caster, 1955 — Silurian, USA
- Acutiramus macrophthalmus (Hall, 1859) — Silurian USA & Canada
- = Pterygotus osborni Hall, 1859 — Silurian , USA
- = 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 bohemicus (Barrande, 1872) — Silurian, Czech Republic