Alternative combinations: Merychyus harrisonensis, Paramerychyus harrisonensis, Ticholeptus harrisonensis
Synonyms: Hypsiops luskensis Schultz and Falkenbach 1950, Merychyus siouxensis Loomis 1924, Phenacocoelus kayi Schultz and Falkenbach 1950, Phenacocoelus luskensis Schultz and Falkenbach 1950
Full reference: O. A. Peterson. 1907. Annals of Carnegie Museum 4(3)
- Merycoides harrisonensis: Its type locality is Van Tassel (Lower), which is in a Harrisonian terrestrial horizon in Wyoming
- Hypsiops luskensis: F:AM 44853A, a partial skeleton (skull, mandible, and probably associated postcranial elements). Its type locality is Eighteen Mile District, which is in a Harrisonian terrestrial horizon in Wyoming.
- Merychyus siouxensis:
- Phenacocoelus kayi: Its type locality is Southeast of Lusk, which is in a Harrisonian terrestrial horizon in the Upper Harrison Beds Formation of Wyoming.
Average measurements (in mm): P1 8.43 x 6.64, P2 11.4 x 9.5, P3 10.8 x 10.6, P4 9.75 x 13.35, M1 13.3 x 14.6, M2 16.7 x 17.9, M3 20.8 x 18.4, m1 13.8 x 11.3