The exact relationship of Drepanopterus to other eurypterids has long been unclear; however, it is now apparent that it is a primitive mycteropoid, and an early relative of the Carboniferous Hibbertopterus.

Drepanopterus is distinguished by its "fairly large" size, compound eyes with parallel axes on a subrectangular to subovate prosoma (head).

[2] Whilst classified as the basalmost member of the Drepanopteridae, Drepanopterus also shares certain characteristics with the kokomopteroids (such as having a clavate telson).

Drepanopterus also has certain characteristics otherwise only found within the Mycteroptidae; appendage IV was not used in food capture and the coxae are large, as in Megarachne.

Appendage III also retains some Hughmilleria-type conical spines suggesting that Drepanopterus hunted larger invertebrate or vertebrate prey than its later relatives.