Erettopterus is a genus 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...

. It was related to another large 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...

, Pterygotus

Pterygotus

Pterygotus is the second-largest known eurypterid, or sea scorpion and one of the largest arthropods of all time.-Description:...

.

Description

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:...

, 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 Devonian

Devonian

The Devonian is a geologic period and system of the Paleozoic Era spanning from the end of the Silurian Period, about 416.0 ± 2.8 Mya , to the beginning of the Carboniferous Period, about 359.2 ± 2.5 Mya...

 periods, were characterized by small to large exoskeletons with semilunar scales. The telson

Telson

The telson is the last division of the body of a crustacean. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments. It never carries any appendages, but a forked "tail" called the caudal furca is often present. Together with the...

, (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

Chelicerae

The chelicerae are mouthparts of the Chelicerata, an arthropod subphylum that includes arachnids, Merostomata , and Pycnogonida . Chelicerae are pointed appendages which are used to grasp food, and are found in place of the chewing mandibles most other arthropods have...

 (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.

Erettopterus 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 its telson, which is bilobed. The distal margins of the chelicerae are angular. The prosoma (head) is semielliptical, with compound eyes located at the edge.

Species

• Erettopterus Salter in Huxley & Salter, 1859
  • Erettopterus bilobus (Salter, 1856) — Silurian, Scotland
    • = Eurypterus perornatus Salter, 1856 — Silurian , Scotland
    • = Pterygotus bilobus var. acidens Woodward, 1878 — Silurian , Scotland
    • = Pterygotus bilobus var. crassus Woodward, 1878 — Silurian, Scotland
    • = Pterygotus bilobus var. inornatus Woodward, 1878 — Silurian, Scotland
    • = Pterygotus bilobus var. perornatus Woodward, 1878 — Silurian, Scotland
    • = Pterygotus perornatus var. plicatissimus Salter in Huxley & Salter, 1859 — Silurian, Scotland
  • Erettopterus brodiei Kjellesvig-Waering, 1961 — Silurian, England
  • Erettopterus canadensis (Dawson, 1879) — Silurian, Canada
  • Erettopterus exophthalmus Kjellesvig-Waering & Leutze, 1966 — Silurian, USA
  • Erettopterus gigas Salter in Huxley & Salter, 1859 — Silurian, England
  • Erettopterus globiceps Clarke & Ruedemann, 1912 — Silurian, USA
  • Erettopterus grandis Pohlman, 1881 — Silurian, USA
  • Erettopterus holmi (Størmer, 1934) — Silurian, Norway
  • Erettopterus laticauda Schmidt, 1883 — Silurian, Estonia
  • Erettopterus marstoni Kjellesvig-Waering, 1961 — Silurian, England
  • Erettopterus megalodon Kjellesvig-Waering, 1961 — Silurian, England
  • Erettopterus osiliensis Schmidt, 1883 — Siluria, Estonia,
  • Erettopterus saetiger Kjellesvig-Waering, 1964 — Silurian, USA
  • Erettopterus serratus Kjellesvig-Waering, 1961 — Devonian, USA
  • Erettopterus spatulatus Kjellesvig-Waering, 1961 — Silurian, England
  • ?Erettopterus vogti Størmer, 1934a — Devonian, Norway
  • Erettopterus waylandsmithi Kjellesvig-Waering & Caster, 1955 — Silurian, USA