Isolated fossil remains of a large chelicera (frontal appendage) suggests that the largest known species, P. grandidentatus, reached a body length of 1.75 metres (5.7 ft).

[1] Like its close relative Jaekelopterus, Pterygotus was a large and active predator noted for its robust and enlarged cheliceral claws that would have allowed it to puncture and grasp prey and a visual acuity (clarity of vision) comparable to that of modern predatory arthropods.

[3] P. anglicus, the type species, grew to 1.6 metres (5.2 ft) in length, based on a large tergite discovered by Henry Woodward at some point between 1866 and 1878.

[14] 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.

[12] 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.

[17] In 1912, the family Pterygotidae was erected by John Mason Clarke & Rudolf Ruedemann in 1912 to include the eurypterid genera Pterygotus, Slimonia, Hughmilleria and Hastimima.

The fossils referred to P. australis, consisting of four fragments making up about half of a segment that were discovered during the process of excavations beneath Melbourne during the construction of new drainage works for the city in 1899.

[20] Kjellesvig-Waering named the species P. bolivianus in 1964 based on fossils recovered from deposits of Emsian-Eifelian (Early to Middle Devonian) age in Bolivia.

[22] Another species, P. ventricosus, was classified as the separate genus Ciurcopterus in 2007 by O. Erik Tetlie and Derek E. G. Briggs, distinguished primarily by sharing several features with more basal pterygotioid eurypterids, such as its appendages being similar to those of Slimonia.

[23] New fossil finds also revealed the presence of Pterygotus in several European countries where it had previously been unknown and established it as a highly taxonomically diverse genus.

As pterygotids commonly occur in association with multiple related genera, it was considered unusual that there was only one species, Erettopterus bilobus, present in Lesmahagow.

This partial ramus measures 1.4 cm (0.5 in) in length and was discovered at Whitcliffe in Shropshire, England associated with fossils of brachiopods and cephalopods.

[12] P. lightbodyi is named in honor of Robert Lightbody, a British amateur geologist who made valuable contributions to paleontological research on the early Paleozoic of the Welsh Borderland, including the discovery of important Silurian fossils (such as eurypterids), in the 1800s.

P. grandidentatus can easily be distinguished from other species not only be its unusual terminal tooth, but also by the disoriented teeth along the claw, being bent in a variety of different directions.

Named by Salter in 1868, P. taurinus is treated as a dubious species for the reason that it is effectively a composite composed of fossils of three different eurypterids.

[28] John William Dawson in 1861 named a new species of lycopod plant, Selaginites formosus, based on alleged remains of stems and branches found at Gaspé.

The outline and position of the eyes suggest an assignation to the genus Pterygotus, differing from P. monroensis in being nearly rectangular in shape and with a straight transverse frontal margin.

[31] Although it was later placed on the genus Waeringopterus, Samuel J. Ciurca, Jr. and O. Erik Tetlie concluded in 2007 that the holotype does not really have eyes and is nothing more than an incomplete body segment.

[17] P. floridanus, recovered from deposits of Lochkovian age in Florida, extended the known range of eurypterids on the continent over 800 km (500 miles) south.

The remains of P. floridanus were first uncovered by G. Arthur Cooper in Suwannee County, Florida, and the fossils consist of a fixed ramus of the chelicera as well as fragments of the abdominal plates and tergites and were concluded to represent a new species of Pterygotus by Erik N. Kjellesvig-Waering in 1950.

A species of Jaekelopterus, J. howelli from the Early Devonian, is similar in the wide and truncated telson shape, but is easily distinguished by possessing serrations and a much larger terminal spine.

[9] The species P. monroensis, known from deposits of late Wenlock to Ludlow age in New York State, USA, was suggested to represent a synonym of Erettopterus osiliensis by Samuel J. Ciurca, Jr. and O. Erik Tetlie in 2007, based upon the similar shape of the eyes and the carapace.

The cladogram also contains the maximum sizes reached by the species in question, which have been suggested to possibly have been an evolutionary trait of the group per Cope's rule ("phyletic gigantism").

[36] Both Pterygotus anglicus and Jaekelopterus rhenaniae had a very high visual acuity, which researchers could determine by observing a low IOA and a large number of lenses in their compound eyes.

The chelicerae of Pterygotus were enlarged, robust and possessed a curved free ramus and denticles of different lengths and sizes, all adaptations that correspond to strong puncturing and grasping abilities in extant scorpions and crustaceans.

Based on the feeding process seen in modern arthropods with chelicerae, one of the claws would hold the prey while the other would cut off pieces and transport it to the mouth with continuous and simple movements.

[44] P. nobilis lived alongside representatives of Acutiramus, Erettopterus and Eusarcana as well as with a diverse fauna of conodonts, gastropods, cephalopods, ostracods, malacostracans, trilobites and bivalves and cartilaginous fish Onchus.

P. ludensis, Downtonian in age, occurred together with a diverse array of eurypterids composed of Carcinosoma, Dolichopterus, Erettopterus, Hughmilleria, Parahughmilleria, Eurypterus, Nanahughmilleria, Marsupipterus, Stylonurus, Tarsopterella, Slimonia and Salteropterus.

[48] The dubious P. taurinus from England has been found in deposits that have also yielded the remains of Erettopterus as well as a variety of fish, such as acanthodians, thelodontiforms as well as cephalaspidomorphs Hemicyclaspis and Thyestes.

[50] P. gaspesiensis from Canada has been recovered from an environment home to a diverse set of bivalves and gastropods as well as the trilobite Phacops and malacostracan Tropidocaris, but no other known eurypterids.