Genus: Agathaumas COPE,1872
Etymology: Greek, agan, “much” and Greek, thaumas, personified form of Greek, thauma, “wonder, prodigy”: “great wonder”.
= Agathaumus HAY, 1901 (sic)

Species: sylvestris COPE, 1872
Etymology: Latin, sylvestris, "forested, wooded."
= Agathaumas silvestre COPE, 1892 (sic)
= Agathaumas sylvestre COPE, 1890 (not 1889) (sic)
= Triceratops sylvestris (COPE, 1872) KUHN, 1936 (nomen dubium)
= Triceratops silvestris (COPE, 1872) (KUHN, 1936 (nomen dubium)

Holotype: AMNH 4000

Locality: 1/2 miles east of Black Buttes station on the Union Pacific Railroad, Black Buttes, 52 miles east of Green River, Sweetwater County, sec. 9, T18N, R100W, Wyoming.

Horizon: Lance Formation.

Biostratigraphy:

Age: Lancian age, upper Maastrichtian Stage, uppermost Senonian subepoch, Upper Gulf Epoch, Late Cretaceous.

Material: Right ilium, 8 posterior dorsal and sacral centra, right ilium, and ribs, proximal portion of a pubis? and other fragments.

Referred material:

COPE, 1892

Locality: Dakota.

Horizon:

Biostratigraphy:

Age: Late Cretaceous.

Material:

Number: Not given: Ilium and tibia.