Erettopterus

Erettopterus Temporal range: Rhuddanian–Lochkovian 443.7–412.3 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Fossil of E. bilobus at the Natural History Museum, Vienna.
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Arthropoda
Subphylum:	Chelicerata
Order:	†Eurypterida
Superfamily:	†Pterygotioidea
Family:	†Pterygotidae
Genus:	†Erettopterus Salter in Huxley & Salter, 1859
Type species
†Erettopterus bilobus Salter, 1856
Species
19 species †E. bilobus Salter, 1856 †E. brodiei Kjellesvig-Waering, 1961 †E. canadensis Dawson, 1879 †E. carinatus Kjellesvig-Waering, 1979 †E. exophthalmus Kjellesvig-Waering & Leutze, 1966 †E. gigas Salter in Huxley & Salter, 1859 †E. globiceps Clarke & Ruedemann, 1912 †E. grandis Pohlman, 1881 †E. holmi Størmer, 1934 †E. laticauda Schmidt, 1883 †E. marstoni Kjellesvig-Waering, 1961 †E. megalodon Kjellesvig-Waering, 1961 †E. osiliensis Schmidt, 1883 †E. saetiger Kjellesvig-Waering, 1964 †E. serratus Kjellesvig-Waering, 1961 †E. serricaudatus Kjellesvig-Waering, 1979 †E. spatulatus Kjellesvig-Waering, 1961 †?E. vogti Størmer, 1934 †E. waylandsmithi Kjellesvig-Waering & Caster, 1955
Synonyms
Himantopterus Salter, 1856, preoccupied Truncatiramus Kjellesvig-Waering, 1961

Erettopterus is a genus of large predatory eurypterid, an extinct group of aquatic arthropods. Fossils of Erettopterus have been discovered in deposits ranging from Early Silurian (the Rhuddanian age) to the Early Devonian (the Lochkovian age), and have been referred to several different species. Fossils have been recovered from two continents; Europe and North America. The genus name is composed by the Ancient Greek words ἐρέττω (eréttō), which means "rower", and πτερόν (pterón), which means "wing", and therefore, "rower wing".

Erettopterus is classified as part of the eurypterid family Pterygotidae, a family differentiated from other eurypterids by their flattened telsons (the most posterior segment of the body) and their modified chelicerae (frontal appendages), ending in well-developed chelae (claws). Although some pterygotid eurypterids, such as Jaekelopterus or Acutiramus grew to gigantic proportions, it is estimated that the largest species of Erettopterus, E. osiliensis, reached 90 cm (35 in). Erettopterus had a bilobed (divided into two lobes) telson, which is its main characteristic. The forms of chelicerae are very diverse between species, but they are generally very long with small curved teeth without serrations.

Studies on the chelicerae and compound eyes of Erettopterus have revealed that it was a predator with high visual acuity, but it was not as highly specialized or active as Jaekelopterus and Pterygotus, it was more like Slimonia acuminata, and probably used its enlarged chelicerae for grasping rather than a more specialized feeding.