page_title: Adelophthalmus
section_title: Twentieth century
hierarchical_section_title: Adelophthalmus / History of research / Twentieth century
caption_attribution_description: English: Fossils of the eurypterid species Adelophthalmus dumonti. Fig. 1 a. First thoracic segment b. Last thoracic segment, with its triangular upraised area c. Marginal spiniferous processes, without striæ, of the segment d. Granules on the carapace e. Articulating surface of the thoracic and abdominal segments f. Marginal ridge of the cephalic shield g. Right eye h. Protruded lateroposterior angles of the shield i. Hollows corresponding with the basal joints of the ectognaths j. Swimming-foot, showing the terminal palette with the rounded and regular outline of its end k. U-shaped ridge Fig. 2 Marginal ridge of the cephalic shield Fig. 3 First appendage, to show the knob or pad on the posterior border of the articulation Fig. 4 Triangular upraised area of the last thoracic segment as seen from the left, to show its slopes
context_page_description: Adelophthalmus is a genus of eurypterid, an extinct group of aquatic arthropods. Fossils of Adelophthalmus have been discovered in deposits ranging in age from the Early Devonian to the Early Permian, which makes it the longest lived of all known eurypterid genera, with a total temporal range of over 120 million years. Adelopthtalmus was the final genus of the Eurypterina suborder of eurypterids and consisted the only known genus of swimming eurypterids from the Middle Devonian until its extinction during the Permian, after which the few surviving eurypterids were all walking forms of the suborder Stylonurina.
  Fossils of Adelophthalmus have been described from four continents; North America, Europe, Asia, Australia, which indicates that Adelophthalmus might have had a nearly cosmopolitan distribution, one of few eurypterid genera to achieve one besides potentially Pterygotus. The territorial expansion of Adelophthalmus had begun early, with representatives found in both Siberia and Australia during the Devonian, but it first gained its almost cosmopolitan distribution following the amalgamation of the supercontinent Pangaea during the Carboniferous and Permian.
context_section_description: In 1907, Henry Woodward described Eurypterus moyseyi (today recognized as Adelophthalmus moyseyi) based on fossils recovered from Radstock, Somerset in England. Woodward compared the singular specimen of E. moyseyi to fossil specimens of A. mansfieldi from America, finding the spikes along the abdomen very similar, though noted that they were less prominent in E. moyseyi. Woodward described very large fossil specimens, the carapace alone measuring 21 cm (8.3 in) and the seven associated body segments measuring an additional 25 cm (9.8) together. Despite this, the latest available size estimates for A. moyseyi put the species at 12 cm (4.7 in) in length.
  A. nebraskensis was described as Eurypterus (Anthraconectes) nebraskensis in 1914 by American geologist Erwin H. Barbour based on fossils recovered in Nebraska, USA. The species was described alongside other fossils from the associated sediments, which helped reinforce the idea as Adelophthalmus (or Anthraconectes) as a freshwater animal.
  The species A. dumonti, Carboniferous in age, was described by Belgian paleontologist Xavier Stainier in 1915 as Eurypterus dumonti. The type specimen, a relatively complete fossil measuring just 3.3 centimetres (1.3 in) in length, was discovered through boring at a new coalfield in Campine, northern Belgium. Though the fossil had been slightly damaged, including the entire counterpart being fragmented, owing to careless usage of hammers and diamond bores during excavation, the fossil could nevertheless be studied in detail and compared to known eurypterid species. As Stainier considered every known Carboniferous eurypterid to be part of the genus Eurypterus (among them several species today recognized as Adelophthalmus, such as the type species A. granosus, A. imhofi and A. pennsylvanicus), he classified the new Belgian eurypterid in that genus as well. He did note that the new species was very similar to species such as E. pennsylvanicus and especially E. mansfieldi (both seen as species of Adelophthalmus today). The species name dumonti honors the prominent Belgian geologist André Dumont.
  The American geologist Amadeus William Grabau described the species Anthraconectes chinensis in 1920, based on fossils discovered in Zhaozezhuang, China.
  Canadian geologist Walter A. Bell described the species A. brasdorensis in 1922 (as a species of Anthraconectes) based on a single fossil recovered in New Campbellton, Canada, referring it to the genus due to similarities with the Scottish A. kidstoni and the American A. mansfieldi.
  1924 saw the description of the species Anthraconectes sellardsi by American paleontologist Carl Owen Dunbar based on two incomplete fossils and few other small fragments from Elmo in Kansas. The first specimen preserves the carapace and the first four tergites of the preabdomen, while the second preserves five preabdominal and three postabdominal tergites; this specimen represents twice the size of the first one.
  The species A. oklahomensis was described by American paleontologist Carl E. Decker in 1938 based on Permian-age fossils in Oklahoma. Since the A. oklahomensis specimen was virtually identical to specimens of A. sellardsi of similar age and a similar stratigraphical horizon in Kansas, A. oklahomensis was designated a junior synonym of A. sellardsi by American geologist Carl Colton Branson, with the support of Decker, in 1959.
  The type specimen of A. zadrai, MB.A. 889, was collected in the Czech Republic in 1930 or 1931 and first mentioned in a manuscript by French Carboniferous worker Pierre Pruvost, who dubbed it "Eurypterus (Anthraconectes) Zadrai", but he did not formally describe the specimen or taxon. Pruvost had previous experience with the genus, having described the species Anthraconectes cambieri in 1930 based on fossils from Charleroi, Belgium. A. zadrai was first described formally in 1952 as Adelophthalmus zadrai, at a point in time when the type specimen was seemingly lost. The specimen was rediscovered in Berlin under a different species name based on the original collector of the fossil (Dr. Pali
caption: Drawing of the type specimen of A. dumonti from its 1915 description (as Eurypterus dumonti).
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