"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. This species was one of the most common eurypterid in England during the Ludlow epoch and was quite large and clearly distinct (though it resembles "P. barrandei", "P. floridanus" and "P. cobbi" in its cheliceral morphology) from other species of the genus, being known from multiple specimens. The most important fossils of "P. lightbodyi" include the holotype (consisting of most of a chelicera) and two paratypes (including most of the free ramus). The claws of "P. lightbodyi" are all equipped with vertically placed and very long teeth, most of which curve slightly backwards. The terminal tooth is unusually slender and long in "P. lightbodyi", and as with the other teeth slightly curved backwards. Among the more important diagnostic features of the species is the combination of a large terminal tooth and a large upright tooth near it.