 In a 1994 paper, S. Christopher Bennett like Lydekker considered "Ornithostoma" to be distinct from "Pteranodon", mainly because of the lower edge ridges of the jaw.He also concluded that it was a "nomen dubium".This in 2001 was rejected however, by David Unwin who thought "Ornithostoma" to be a valid genus belonging to the Pteranodontidae, but limited the referable material to the original three fragments, including perhaps CAMSM B.54406.