Similarities in the genital appendage could mean that the three genera are all synonyms of each other, as they had been classified in the past (as species of "Pterygotus"). Some differences between them have also been noted in the chelicerae, though chelicerae have been questioned as the basis of eurypterid generic distinction since their morphology depends on the lifestyles and has been observed to vary throughout ontogeny. Telson morphology is sometimes used as a distinguishing feature, though the telsons of the three derived pterygotid genera are all paddle-shaped (the telson of "Jaekelopterus" is triangular, but might fall into the morphological range of the other genera). An inclusive phylogenetic analysis with multiple species of "Acutiramus", "Pterygotus" and "Jaekelopterus" is required to resolve whether or not the genera are synonyms of each other.