Genus: Pteropleyx COPE, 1890 (not 1889) (nomen dubium)
Etymology: Greek, pteron, “wing, feather”, and Greek, pelyx, “pelvis, basin”: “wing pelvis”.
= Petropelyx KEYES, 1894 (sic)

Species: grallipes COPE, 1890 (not 1889) (nomen dubium)
Etymology: Latin, grallator, "one who walks on silts" and Greek, pes, "foot."
= Thespesius grallipes (COPE, 1890) (nomen dubium)
= Trachodon grallipes (COPE, 1890) (nomen dubium)

Holotype: AMNH 3971

Locality: Cow Island 40 miles below mouth of Judith River on the Missouri River, Fergus County, Montana.

Horizon: Judith River Formation.

Biostratigraphy:

Age: Judithian age, Campanian Stage, Senonian subepoch, Upper Gulf epoch, Late Cretaceous.

Material: Greater part of skeleton.