"P. carmani" is the most commonly found eurypterid in the Lower Devonian deposits of Lucas County, Ohio. Described by Erik N. Kjellesvig-Waering in 1961 and named in honor of Dr. J. Ernest Carman of the Ohio State University, the first to discover eurypterids at the locality where the "P. carmani" remains were found, "P. carmani" is primarily known from incomplete chelicerae and gnathobases of coxae. Alongside the two coxae and three chelicerae part of its original description, known fossil remains also include a metastoma and a pretelson. All of these original fossil specimens were designated by Kjellesvig-Waering as paratype specimens upon the original description of the species. The designated type specimen is an incomplete chelicerae, PE5105, that remains housed at the Chicago Natural History Museum alongside the paratype specimens. The species can be differentiated from other species of "Pterygotus" primarily by features of its cheliceral teeth, differing from "P. barrandei" and "P. cobbi" in these teeth being less-developed and thicker in "P. carmani" as well as the teeth having a markedly different arrangement on the claw.