Species: altus MARSH, 1893
Etymology:
Holotype: YPM 515
Locality: 1 mile above the mouth of Dog Creek, near the mouth of the Judith River, Fergus County, Montana.
Horizon: Judith River Formation.
Biostratigraphy:
Age: Judithian age, Campanian Stage, Senonian subepoch, Upper Gulf epoch, Late Cretaceous.
Material: Right tibia missing distal end.
Referred material:
= Hesperornis montana SHUFELDT, 1915
Etymology:Holotype: USNM 8199
Locality: 1 mile above mouth of Dog Creek, Fergus County, Montana.
Horizon: Claggett Formation.
Biostratigraphy:
Age: Campanian Stage, Senonian Subepoch, Gulf Epoch, Late Cretaceous.
Material: 23rd dorsal vertebra.