This timeline of eurypterid research is a chronologically ordered list of important fossil discoveries, controversies of interpretation, and taxonomic revisions of eurypterids, a group of extinct aquatic arthropods closely related to modern arachnids and horseshoe crabs that lived during the Paleozoic Era. The scientific study of eurypterids began in the early 19th century when James E. DeKay recognized a fossil that had previously been described as that of a fish as arthropod in nature. Though DeKay erroneously believed the fossil to represent a crustacean and a missing link between trilobites and branchiopods, the fossil became the type species of first ever eurypterid to be scientifically described, Eurypterus remipes, in 1825. Over 250 species of eurypterids in 74 recognized valid genera have been described since the discovery of Eurypterus remipes. The most recent genus to be described is Terropterus (2021) and the most recent species is its type species Terropterus xiushanensis (2021).
19th century
1810s
1818 The first eurypterid fossil to be discovered is unearthed in rocks in New York of Silurian age. It is described by Dr. S. L. Mitchill as an example of the fish Silurus, possibly due to the catfish-like appearance of its carapace.
1820s
1825 James E. DeKay recognized the fossil described by Mitchill as an arthropod and named it Eurypterus remipes, the first eurypterid to be described scientifically. DeKay interpreted the animal as a crustacean and as the missing link between trilobites and branchiopods.
1830s
1831 John Scouler examines and figures fossil remains from Lower Carboniferous Scotland which will later be referred to Hibbertopterus scouleri. Scouler described the genus Eidothea based on a single fossil without designating a species name.
1836 Samuel Hibbert describes the species Eurypterus scouleri, later transferred to its own genus, Hibbertopterus. Scouler's Eidothea is discovered to be pre-occupied by a genus of plant, his fossil is found to be similar to Eurypterus scouleri.
1838 Stepan S. Kutorga described the species Limulus oculatus as an extinct horseshoe crab.
1839 Louis Agassiz described the new genus Pterygotus, believing the fossils to represent a large fish.
1840s
1843 Burmeister created the family Eurypteridae to contain Eurypterus.
1844 Agassiz recognized Pterygotus as an arthropod after the discovery of more complete remains, he classified it as a crustacean of the Entomostraca subclass.
1849 Agassiz described the species Pterygotus anglicus.
1850s
1851 Hermann Jordan excavates the first fossils of the genus Adelophthalmus.
1852 John William Salter described the species Pterygotus problematicus.
1854 Jordan and Hermann von Meyer describe the new species and genus Adelophthalmus granosus.
1855 August Emanuel von Reuss described the new species and genus Lepidoderma imhofi.
1856 Salter described the new genus Himantopterus (the genus name was replaced in 1859 by Erettopterus) and the new species H. acuminatus, H. banksii, H. bilobus, H. lanceolatus, H. maximus and H. perornatus. Salter described the species Pterygotus acuminata. Page transferred Pterygotus acuminata to its own genus, Slimonia. Page named and figured, but did not thoroughly describe, the genus Stylonurus.
1859 Hall describes the species Pterygotus marcophthalmus. It will later be considered part of the genus Acutiramus. Hall describes the species Pterygotus osborni. Hall describes the species Pterygotus cobbi. Salter names a subgenus of Pterygotus, Erettopterus, for species with a bilobed telson. Salter described the species Slimonia stylops. Salter described the species Eurypterus abbreviatus. Salter described the species Pterygotus ludensis. Salter described the species Pterygotus punctatus. Salter described the species Eurypterus pygmaeus, later recognized as representing fossils of Nanahughmilleria. Salter and Thomas Henry Huxley describe the fossil specimens that will later be named Necrogammarus salweyi, believing them to represent some sort of crustacean.
1860s
1860 Edouard D'Eichwald recognized Kutorga's Limulus oculatus to be highly distinct from Limulus and created the generic name Campylocephalus to contain the species.
1861 John William Dawson named a new species of plant, Selaginites formosus.
1865 Henry Woodward described the genus Stylonurus (named and figured, but not thoroughly described, by David Page in 1856) and raised the rank of the Eurypteridae to that of order, effectively creating the Eurypterida as the taxonomic unit it is seen as today.
1866 Woodward created the subclass Merostomata to contain eurypterids and xiphosurans. Ernst Haeckel classified the Merostomata (containing virtually only the Eurypterida) and Xiphosura within a group he named Gigantostraca within the crustaceans. "Gigantostraca" is later treated as a synonym of Mersostomata.
1868 Salter described the species Pterygotus taurinus. Woodward described the species Eurypterus obesus. Woodward described the species Eurypterus scorpioides. Fielding Bradford Meek and Amos Henry Worthen described the new species and genus Anthraconectes mazonensis. Anthraconectes was designated a subgenus of Eurypterus.
1870s
1870 Henry Woodward described the species Necrogammarus salweyi, believing it to represent an amphipod.
1871 Dawson reclassified his plant Selaginites formosus as a eurypterid.
1872 Barrande describes Pterygotus bohemicus, later considered part of the genus Acutiramus, P. kopaninensis and P. nobilis. Walcott described the genus and species Echinognathus clevelandi.
1873 Friedrich Goldenberg coined the name Polyzosternites to replace Adelophthalmus.
1874 Samuel Almond Miller described the new genus and species Megalograptus welchi, mistakenly believing the fragmentary fossils to represent a graptolite.
1875 Grote and Pitt describe Pterygotus cummingsi, later considered the type species of Acutiramus. Grote and Pitt describe the species Eusarcus scorpionis.
1877 Dionýs Štúr described the species Eurypterus salmi, later referred to Campylocephalus. Meek and Worthen described the species Eurypterus pennsylvanicus, later referred to Adelophthalmus. Hall described the species Eurypterus mansfieldi, later referred to Adelophthalmus.
1879 John William Dawson described the species Erettopterus canadensis.
1880s
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