This taxon is considered subjective synonym of
of the valid taxon Centrosaurus apertus
according to the Paleobiology Database.
See the page for Centrosaurus apertus →
Bibliography
Original description
B. Brown. 1917. A complete skeleton of the horned dinosaur Monoclonius, and description of a second skeleton showing skin impressions. Bulletin of the American Museum of Natural History 37(10):281-306