page_title: Eysyslopterus
section_title: History of research
hierarchical_section_title: Eysyslopterus / History of research
caption_attribution_description: English: Outdated 1934 restoration of the carapace of the eurypterid species Hughmilleria patteni (now in the genus Eysyslopterus), based on Størmer, 1934.
context_page_description: Eysyslopterus is a genus of eurypterid, an extinct group of aquatic arthropods. Eysyslopterus is classified as part of the family Adelophthalmidae, the only clade within the derived Adelophthalmoidea superfamily of eurypterids. One fossil of the single and type species, E. patteni, has been discovered in deposits of the Late Silurian period in Saaremaa, Estonia. The genus is named after Eysysla, the Viking name for Saaremaa, and opterus, a traditional suffix for the eurypterid genera, meaning "wing". The species name honors William Patten, an American biologist and zoologist who discovered the only known fossil of Eysyslopterus.
  Eysyslopterus is a little-known basal genus that was distinguished from the rest of adelophthalmids by the position near the head margin of the eyes, different from the rest of its relatives. Its carapace was parabolic and with transverse deep furrows forming the ornamentation. With an estimated length of 8 cm, Eysyslopterus was a small eurypterid. It lived in a nearshore lagoonal quiet community along other eurypterid species.
context_section_description: Eysyslopterus is only known from one single specimen (and is therefore the holotype, AMNH 32720, housed at the American Museum of Natural History) which preserves the carapace. This fossil was collected by the American biologist and zoologist William Patten during his extensive explorations at the Rootsikula Formation in Saaremaa, Estonia (then part of the Soviet Union). During a meeting between Patten and the Norwegian paleontologist and geologist Leif Størmer in 1932, Størmer observed Patten's private collection of eurypterids, among which he recognized a carapace of a new unknown species. He described it in 1934 as belonging to the genus Hughmilleria patteni, named after Patten, who died months after the meeting. Størmer noticed several differences between his new species and other Hughmilleria species, essentially the shape of the prosoma and the form or position of the eyes. He also suggested a close relationship between H. patteni and other species, especially the Scottish species H. lanceolata.
  However, in 1961, the American paleontologist Erik Norman Kjellesvig-Waering split Hughmilleria in two subgenera, H. (Hughmilleria) for species with large ovoid marginal eyes and H. (Nanahughmilleria) for small reniform intramarginal (within the margin) eyes. Since H. patteni fulfilled this condition, it was referred to H. (Nanahughmilleria). It was not until 2008 when during a phylogenetic review of the entire Adelophthalmidae family by the Norwegian Odd Erik Tetlie and German Markus Poschmann paleontologists, N. patteni was recognized as sufficiently different to represent its own genus due to the anterior position of its eyes, much more exaggerated than in the other adelophthalmid genera. The first part of the generic name is composed of the word Eysysla, the Viking name for Saaremaa, and the second part by opterus, a suffix commonly used in eurypterids which means "wing" (and therefore, translated as "wing of Eysysla").
caption: Restoration of the carapace of Eysyslopterus patteni based on Størmer's of 1934
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