Pterygotus atlanticus

Pterygotus is a genus of giant predatory eurypterid, a group of extinct aquatic arthropods. Fossils of Pterygotus have been discovered in deposits ranging in age from Late Silurian to Late Devonian, and have been referred to several different species. Fossils have been recovered from four continents; Australia, Europe, North America and South America, which indicates that Pterygotus might have had a nearly cosmopolitan distribution. The type species, P. anglicus, was described by Swiss naturalist Louis Agassiz in 1839. Agassiz mistakenly believed the remains were of a giant fish, with the name Pterygotus translating to "winged fish". He would only realize the mistake five years later in 1844.

With the largest species, P. grandidentatus, reaching a body length of 1.75 metres, Pterygotus was among the largest known eurypterids to have existed, though some of its close relatives surpassed it in length. Though there were a few gigantic species, many species were considerably smaller in size. The smallest species, P. kopaninensis, measured just 50 centimetres in length.
 * Initial finds The first fossils of Pterygotus were found in deposits of Lochkovian-Pragian age by quarrymen in Scotland and western England, who referred to the large fossil remains as "Seraphims".
 * Creation of subgenera and the Pterygotidae By 1859, 10 species had been assigned to the genus, and John William Salter recognized that it was possible to divide these species into subgenera based on the morphology of the telsons. Salter erected the subgenus Pterygotus for species with a bilobed telson.
 * Further discoveries Though early discoveries of Pterygotus were confined to England and North America, fossil finds throughout the 20th century would help establish that Pterygotus as a genus achieved a nearly cosmopolitan distribution.
 * The cheliceral morphology and visual acuity of the pterygotid eurypterids separates them into distinct ecological groups. The primary method for determining visual acuity in arthropods is by determining the number of lenses in their compound eyes and the interommatidial angle. The IOA is especially important as it can be used to distinguish different ecological roles in arthropods, being low in modern active arthropod predators.
 * Like Acutiramus, Pterygotus lived in fully marine environments, and its fossils are today recovered associated with common and diverse fossils indicative of such an environment. Notably, P. barrandei and P. cobbi occur in marine environments associated with fossils of Acutiramus. Pterygotus was more widespread than Acutiramus and as such many species occur without associated representatives of Acutiramus as well, such as the British P. lightbodyi.