page_title: Slimonia
section_title: Classification
hierarchical_section_title: Slimonia / Classification
caption_attribution_description: Pa L&amp;ON T OQRAPH 1, SoC . PI. XX. U. SILURIAN CRUSTACEA. 2 ATHollick,deletlitli WWest'imj SLIMONIA ACUMINATA, SaJttr.sv- (Restored,.)
context_page_description: Slimonia is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Slimonia have been discovered in deposits of Silurian age in South America and Europe. Classified as part of the family Slimonidae alongside the related Salteropterus, the genus contains three valid species, S. acuminata from Lesmahagow, Scotland, S. boliviana from Cochabamba, Bolivia and S. dubia from the Pentland Hills of Scotland and one dubious species, S. stylops, from Herefordshire, England. The generic name is derived from and honors Robert Slimon, a fossil collector and surgeon from Lesmahagow.
  Out of the four described species of Slimonia, three measured below or up to 20 centimetres in length. Only S. acuminata was larger, with the largest specimens measuring 100 centimetres in length. Though this is large for a predatory arthropod, Slimonia would be exceeded in length by later and more derived members of the closely related pterygotid family of eurypterids, which would become the largest known arthropods to ever live.
context_section_description: Slimonia is classified as part of the eurypterid family Slimonidae, within the superfamily Pterygotioidea. Historically Slimonia was first considered a member of the Pterygotidae, until it was reclassified alongside Hughmilleria and other genera to the family Hughmilleriidae in 1951 by Erik N. Kjellesvig-Waering. Nestor Ivanovich Novojilov classified Slimonia as part of a family of its own in 1968.
  Slimonia is one of the most closely related genera to the pterygotid family and the Slimonidae is often interpreted as a sister-taxon to the Pterygotidae. The other Pterygotioid family, the Hughmilleriidae, has also been interpreted as the most closely related sister-taxon to the pterygotids. The discovery of Ciurcopterus, the most primitive known pterygotid, and studies revealing that Ciurcopterus combines features of Slimonia (the appendages are particularly similar) and of more derived pterygotids, revealed that the Slimonidae is more closely related to the Pterygotidae than the Hughmilleriidae is.
  The cladogram below is simplified from a study by O. Erik Tetlie (2007), and showcases the position of Slimonia relative to the rest of the Eurypterina suborder of eurypterids, with the Stylonurina suborder as an outgroup.
caption: Dorsal and ventral views of S. acuminata
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