Oogenus: Triprismatoolithus JACKSON & VARRICCHIO, 2010
Etymology: Latin, tri, "three"; indicating the presence of three structural layers of prismatic egghell calcite, and Greek, oo, "egg" and Greek, lithus, "rock or stone"; Three stone egg.

Oospecies: stephensi JACKSON & VARRICCHIO, 2010
Etymology: In honor of Robert E. 'Short' Stephens of Augusta, Montana.

Holotype: ES 101

Locality: Dave and Joel Quarry, Sevenmile Hill outcrops, Teton County, Montana.

Horizon: Two Medicine Formation.

Biostratigraphy:

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

Material: A compress whole egg.

Referred material:

ES 102, 153, 154, 155, 157, 163: Partial eggs.

MOR 98-31, 98-26, 99-31 ES2, MOR 98-28 ES 1, MOR 98-28 ES 2: Eggshells.

Locality: First Find Micorsite (OTM 99-19), Sevenmile Hill outcrops, Teton County, Montana.

Horizon: Two Medicine Formation.

Biostratigraphy:

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

Material:

ES 127: Abnormal, multilayered eggshell.