page_title: Adelophthalmus
section_title: Classification
hierarchical_section_title: Adelophthalmus / Classification
caption_attribution_description: Figures 43–47 Eurypterus (Anthraconectes) mansfieldi C. E. Hall. Figure 43, a small, fairly perfect specimen, ×3; figure 44, large specimen, natural size, showing the long epimera; figure 45, a nearly entire small individual, showing the extremely slender telson and the doublures of the postabdominal segments; figure 46, the fourth endognathite, ×2; figure 47, enlargement of test with narrow, triangular scales. (From James Hall) The Eurypterida of New York. Volume 1. New York State Museum Memoir 14, figures 43-47
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: Adelophthalmus is classified as part of (and lends its name to) the family Adelophthalmidae, the only family within the superfamily Adelophthalmoidea, alongside the genera Parahughmilleria, Nanahughmilleria, Bassipterus, Pittsfordipterus and Eysyslopterus. The cladogram below presents the inferred phylogenetic positions of most of the genera included in the three most derived superfamilies of the Eurypterina suborder of eurypterids (Adelophthalmoidea, Pterygotioidea and the waeringopteroids), as inferred by O. Erik Tetlie and Markus Poschmann in 2008, based on the results of a 2008 analysis specifically pertaining to the Adelophthalmoidea and a preceding 2004 analysis.
  A close relationship between the three groups is confirmed partly due to basal members of all three groups, Orcanopterus, Eysyslopterus and Herefordopterus, sharing similar carapace shapes. Adelophthalmus being the most derived member of its family is confirmed by its swimming appendages being the thinnest of all included genera and by its eyes being the closest to the center of the carapace. In adelophthalmoids, eyes appear to get closer to the center of the carapace with every more derived genus, and even though eye position may reflect lifestyles and inhabited environments, they are also assumed to (particularly in this case, with a clear progression) include phylogenetically important information.
caption: Fossils of A. mansfieldi.
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