 The foot claws are slightly curved; the fifth toe has been reduced to a single claw.The authors placed "Eosipterus" in a general Pterodactyloidea "incertae sedis"; in 1999 a placement within Pterodactylidae was suggested and even a synonymy with "Pterodactylus" within a hypothesis that the lower Yixian Formation dated from the late Jurassic.A cladistic study in 2006 found that it was a member of the Ctenochasmatidae — David Unwin more precisely assigned it to the Ctenochasmatinae.