Species: altus MARSH, 1893
Etymology: Latin, altus, "high."

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.

Coniornis altus MARSH, 1893, Holotype: YPM 515: A) Posterior; B) cross-section; C) right lateral view; D) ventral; and E) anterior end.

Referred material:

= Hesperornis montana SHUFELDT, 1915
Etymology: In reference to the state of Montana.

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.