Genus: Euthlastus SIMPSON, 1927
Etymology: Greek, eu, “good, ture” and Greek, thlastos, “crushed”: Well crushed (teeth).

Species: cordiformis SIMPSON, 1927
Etymology:

Holotype: YPM 13755

Locality: Reeds YPM Quarry 9, (Mammal Quarry), T22N, R77W, Sec. 12, Como Bluff, Albany County, Wyoming.

Horizon: Brushy Basin Member, Morrison Formation.

Biostratigraphy: Zone 3.

Age: Upper Part, Comobluffian age, Kimmeridgian Stage, uppermost Malm Epoch, Late Jurassic.

Material: Right maxilla with last 4 molars, all somewhat borken.

Referred material:

ENGELMANN & CALLISON, 1998

Locality: Quarry face as exposed inside the Dinosaur National Monument Visitor Center, Carnegie Quarry, Vernal, Uintah County, Utah.

Horizon: Brushy Basin Member, Morrison Formation.

Biostratigraphy: Zone 3.

Age: Upper Part, Comobluffian age, Kimmeridgian Stage, uppermost Malm Epoch, Late Jurassic.

Material:

DINO 12796: Upper molar.