The first fossils of Pterygotus were found in deposits of Lochkovian-Pragian (Early Devonian) age by quarrymen in Scotland and western England, who referred to the large fossil remains as "Seraphims".
Louis Agassiz, a Swiss-American biologist and geologist, described the fossils in 1839 and named it Pterygotus in the belief that they were the fossil remains of a large fish; "Pterygotus" translating to "winged fish".
The specimens described by Agassiz from England were referred to a species he dubbed Pterygotus problematicus.
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.
Although recognizing the fossils of Pterygotus as arthropod was closer to its modern phylogenetical position, Agassiz would consider Pterygotus to represent a crustacean of the Entomostraca subclass.
Although Frederick M'Coy did note that Pterygotus resembled the Limulidae and the previously discovered eurypterid Eurypterus in 1849, he classified both Eurypterus and Pterygotus as crustaceans.

The new Scottish fossils were named as the species P. anglicus in 1849, which remains the most extensively known species of Pterygotus, distinguished from subsequently discovered species by possessing curved terminal teeth and the primary and intermediate teeth being inclined slightly backwards.

P. problematicus was also used as the designation for an incomplete chelicera discovered in the Welsh Borderland of western England by John William Salter in 1852 but is in modern times considered a nomen vanum ("baseless name") as the species is impossible to define.
The fossil material with which it was described is undiagnostic and insufficient to establish any meaningful characteristics and as such many fragmentary pterygotid fossils have been referred to it throughout its long history, rendering it effectively synonymous with the family Pterygotidae.
More often than not, these fragments consist of patches of pterygotid integument preserving the scale-like ornamentation characteristic of the group which researchers have wrongfully believed was characteristic of only Pterygotus or P. problematicus.
As such ornamentation is known from every pterygotid genus it can not be used as a diagnostic feature of a single species.
Though P. problematicus is the earliest name used for a species of Pterygotus, it is not considered the type species as the name is no longer in use.
Instead P. anglicus, based on a number of diagnostic features and properly illustrated in its description by Agassiz in 1844, is considered the type species of Pterygotus.

Two further species that remain assigned to the genus to this day would be described from England during the 19th century; P. ludensis of Pridoli (Late Silurian) age and P. arcuatus of Ludlow (Late Silurian) age, along with a North American species, P. cobbi, from the Pridoli of the United States and Canada.
P. arcuatus was originally described from a syntypic series (a series of specimens out of which a particular holotype is not designated) of fossil remains by John William Salter, containing five separate fossil specimens.
In 1961, 102 years after its description, Erik N. Kjellesvig-Waering noted that only one of these specimens (Number 89587 of the Geological Survey and Museum of London, a free ramus of a chelicera) might truly be referrable to this distinct species as the other fossils (tergites, coxae and indeterminable fragments) might actually represent fossils of other species due to not being diagnostic enough.
P. ludensis, described by Salter in 1859, can be distinguished from other species by the more developed and prolonged keel (or ridge) running along the center of the telson from its beginning to the tail spike.

The rare species P. cobbi, described by James Hall in 1859 based on fossils recovered in New York, USA, was the first species of Pterygotus to be described from outside of Scotland and expanded the known range of the genus considerably.
Hall described this new species along
The first fossils of Pterygotus were found in deposits of Lochkovian-Pragian (Early Devonian) age by quarrymen in Scotland and western England, who referred to the large fossil remains as "Seraphims". Louis Agassiz, a Swiss-American biologist and geologist, described the fossils in 1839 and named it Pterygotus in the belief that they were the fossil remains of a large fish; "Pterygotus" translating to "winged fish". The specimens described by Agassiz from England were referred to a species he dubbed Pterygotus problematicus. 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. Although recognizing the fossils of Pterygotus as arthropod was closer to its modern phylogenetical position, Agassiz would consider Pterygotus to represent a crustacean of the Entomostraca subclass. Although Frederick M'Coy did note that Pterygotus resembled the Limulidae and the previously discovered eurypterid Eurypterus in 1849, he classified both Eurypterus and Pterygotus as crustaceans.
The new Scottish fossils were named as the species P. anglicus in 1849, which remains the most extensively known species of Pterygotus, distinguished from subsequently discovered species by possessing curved terminal teeth and the primary and intermediate teeth being inclined slightly backwards.
P. problematicus was also used as the designation for an incomplete chelicera discovered in the Welsh Borderland of western England by John William Salter in 1852 but is in modern times considered a nomen vanum ("baseless name") as the species is impossible to define. The fossil material with which it was described is undiagnostic and insufficient to establish any meaningful characteristics and as such many fragmentary pterygotid fossils have been referred to it throughout its long history, rendering it effectively synonymous with the family Pterygotidae. More often than not, these fragments consist of patches of pterygotid integument preserving the scale-like ornamentation characteristic of the group which researchers have wrongfully believed was characteristic of only Pterygotus or P. problematicus. As such ornamentation is known from every pterygotid genus it can not be used as a diagnostic feature of a single species. Though P. problematicus is the earliest name used for a species of Pterygotus, it is not considered the type species as the name is no longer in use. Instead P. anglicus, based on a number of diagnostic features and properly illustrated in its description by Agassiz in 1844, is considered the type species of Pterygotus.
Two further species that remain assigned to the genus to this day would be described from England during the 19th century; P. ludensis of Pridoli (Late Silurian) age and P. arcuatus of Ludlow (Late Silurian) age, along with a North American species, P. cobbi, from the Pridoli of the United States and Canada. P. arcuatus was originally described from a syntypic series (a series of specimens out of which a particular holotype is not designated) of fossil remains by John William Salter, containing five separate fossil specimens. In 1961, 102 years after its description, Erik N. Kjellesvig-Waering noted that only one of these specimens (Number 89587 of the Geological Survey and Museum of London, a free ramus of a chelicera) might truly be referrable to this distinct species as the other fossils (tergites, coxae and indeterminable fragments) might actually represent fossils of other species due to not being diagnostic enough. P. ludensis, described by Salter in 1859, can be distinguished from other species by the more developed and prolonged keel (or ridge) running along the center of the telson from its beginning to the tail spike.
The rare species P. cobbi, described by James Hall in 1859 based on fossils recovered in New York, USA, was the first species of Pterygotus to be described from outside of Scotland and expanded the known range of the genus considerably. Hall described this new species along
Pterygotus