page_title: Pterygotioidea
section_title: History of research
hierarchical_section_title: Pterygotioidea / History of research
caption_attribution_description: English: Fossils of Pterygotus problematicus published by John William Salter in 1852. Fig. 1 a. Part of the claw of Pterygotus problematicus, Agass., from the Upper Ludlow Rock of Hagley Park, Herefordshire:— this is probably the fixed finger, and shows the striated spines of unequal size. Fig. 1 b. Some of the spines, magnified. Fig. 2 a. From the same slab:— a portion probably of the spinous edge of the abdomen, with one of the lateral appendages (*) attached. Fig. 2 b. The appendage, fig. 2a*, magnified, to show the radiating striae and lateral teeth. This large spine or appendage may possibly be a terminal joint of one of the feet, pressed against the fragment, fig. 2 a, but not articulated with it.
context_page_description: Pterygotioidea is a superfamily of eurypterids, an extinct group of aquatic arthropods. Pterygotioids were the most derived members of the infraorder Diploperculata and the sister group of the adelophthalmoid eurypterids. The group includes the basal and small hughmilleriids, the larger and specialized slimonids and the famous pterygotids which were equipped with robust and powerful cheliceral claws.
  Though the more primitive hughmilleriids were small, Hughmilleria wangi being the smallest of all pterygotioids at just 6 centimetres in length, later members of the group, particularly in the Pterygotidae, would become the largest known arthropods to ever exist with several genera surpassing 2 metres in length.
  Among all currently recognized eurypterid clades, the Pterygotioidea is the most diverse, containing over 50 species in 10 genera. With the number of recognized eurypterid species being around 250, pterygotioids account for more than a fifth of all known eurypterid species.
context_section_description: The first pterygotioid fossils to be uncovered were those of the type genus, Pterygotus. Louis Agassiz, a Swiss-American biologist and geologist, described the fossils in 1839 and named it Pterygotus in the mistaken belief that they were the fossil remains of a large fish; "Pterygotus" translating to "winged fish". Agassiz first recognized the true nature of the fossils as arthropod remains five years later in 1844 after having examined more complete fossils recovered in the Old Red Sandstone of Scotland.
  In 1856, the species Pterygotus acuminata was named by John William Salter. The fossils referred to this species, recovered from Lesmahagow, Scotland, were soon realized to be distinct from other species of Pterygotus (such as the type species P. anglicus) and that same year geologist David Page erected a new genus to contain the species. The new genus, Slimonia, could be differentiated from other known species of Pterygotus most apparently by the lack of large cheliceral claws, otherwise a defining characteristic of Pterygotus.
  In 1903, the genus Hughmilleria was created based on fossils discovered in the Pittsford Shale Member of the Vernon Formation. Its describer, the American geologist Clifton J. Sarle, considered the genus to represent an intermediate form between the more basal Eurypterus and the derived Pterygotus but did not assign Hughmilleria to any particular family.
  The family Pterygotidae was erected in 1912 by John Mason Clarke and Rudolf Ruedemann to constitute a group for the genera Pterygotus, Slimonia, Hastimima and Hughmilleria. Pterygotus had also been designated as containing two subgenera; Pterygotus (Curviramus) and Pterygotus (Erettopterus), but Erettopterus would later be raised to its own genus. American paleontologist Erik N. Kjellesvig-Waering emended the Pterygotidae in 1951, referring the genera Hastimima, Hughmilleria and Slimonia, and the newly named Grossopterus, to their own family within the Eurypteracea, Hughmilleriidae, leaving Pterygotus as the sole pterygotid genus.
  In 1955, Norwegian paleontolgist and geologist Leif Størmer considered the pterygotid clade to represent a family within the eurypterid superfamily "Eurypteracea". In 1962, Russian paleontologist Nestor Ivanovich Novojilov raised the Eurypteracea and Pterygotidae to subordinal and superfamily status, Eurypteracea becoming the suborder Eurypterina and creating the superfamily Pterygotioidea, containing Hughmilleriidae and Pterygotidae. The same year, Novojilov also reclassified Slimonia into a pterygotioid family of its own as it was considered distinct enough from other hughmilleriids to warrant a separate family, the Slimonidae.
caption: Fossils described by John William Salter as belonging to "Pterygotus problematicus" in 1852. This species is now considered a nomen vanum.
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