Wikipedia
Meniscoessus is a genus of extinct mammal from the Upper Cretaceous Period of what is now North America. It lived toward the end of the "age of the dinosaurs" and was a member of the extinct order Multituberculata. It lies within the suborder Cimolodonta and family Cimolomyidae.
The genus Meniscoessus was named by Cope E.D. in 1882. It has also been known under the following names: '' Cimolomys '' (partly); Dipriodon ( Marsh 1889); Halodon (Marsh 1889); Oracodon (Marsh 1889); Moeniscoessus; Selenacodon (Marsh 1889) (partly); and Tripriodon (Marsh 1889).
The history of this generic name is complicated and confusing. It is attributed to Cope, 1882. Later, this was joined by "Meniscoessus" (Marsh 1889). The second usage apparently related to teeth described as belonging to small carnivorous dinosaurs. These were further christened Dipriodon, Tripriodon and others, including Triprotodon. Close similarities were then noticed with an already established dinosaur genus, Paronychodon (Cope 1876), also based on teeth from the Laramie Formation. Over time, an impressive school of names was synonymized under P. However, this is now considered a nomen dubium.
In 1929, Simpson published American Mesozoic Mammalia (Mem. of the Peabody Museum, 3 pt. 1; i-xv). The name Tripriodon ("three saw tooth") was resurrected. These "theropod" teeth were actually mammalian. The mammal T. since seems to have fallen from use.
Be that all as it may, Meniscoessus is a valid multituberculate, and is known from some quite good remains, as well as a great many teeth.