Catopsbaatar
Scientific classification
Kingdom: Animalia
Therapsida
Class: Mammalia
Order: Multituberculata
Family: Djadochtatheriidae
Genus: Catopsbaatar
Species
  C. catopsaloides

Ref.

Catopsbaatar is a mammal genus which lived in Mongolia during the Upper Cretaceous. It coexisted with some of the late dinosaurs. This animal was a member of the extinct order of Multituberculata.
For those of a technical disposition, it's within the Suborder of Cimolodonta, and a member of the family Djadochtatheriidae.

Genus: Catopsbaatar (Kielan-Jaworowska Z, 1974) Kielan-Jaworowska Z, 1994
Remarks: (For anatomists or masochists): "One of the most characteristic features of Catopsbaatar (which differentiates it not only from Kryptobaatar but from all the djadochtatherioids in which the zygomatic ridges are known ), is a very deep anterior zygomatic ridge, and a small medial zygomatic ridge, the latter forming about a quarter of a circle and adhering the anterior one from behind," (Kielan-Jaworowska et al, 2002).

Species: Catopsbaatar catopsaloides (Kielan-Jaworowska Z, 1974) Kielan-Jaworowska Z, 1994
Aka: Catopsalis caotopsaloides; Djadochtatherium catopsaloides Kielan-Jaworowska, 1974
Place: Hermiin Tsav (aka Khermeen Tsav)
Country: Mongolia
Age: Campanian, Upper Cretaceous
Remarks: This was originally regarded as a species of Djadochtatherium. It also spent a while assigned to the North American genus Catopsalis Cope, 1882, courtesy of an interpretation in 1979 by Kielan-Jaworowska & Sloan.
The original material consisted of three skulls, the most complete of which was juvenile. Subsequently, a fouth specimen was identified and then an even more complete example came to light in 1999, along with some postcranial skeleton. This belonged to an elderly critter. It's been provisionally considered in Kielan-Jaworowska et al, 2002 but has yet to be fully described.
With a skull length of around 6cm, this was a pretty large multi.
References: Kielan-Jaworowska (1974), Multituberculate succesion in the Late Cretaceous of the Gobi Desert (Mongolia). in Results of the Polish-Mongolian Palaeont. Expeditions - Part V. Palaeontologica Polonica. (30), p.23-43.
Kielan-Jaworowska & Sloan (1979), Catopsalis (Multituberculata) from Asia and North America and the problem of taeniolabidid dispersal in the Late Cretaceous. Acta Paleontologica Polonica 24, p.187-197.
Kielan-Jaworowska (1994), A new generic name for the multituberculate mammal "Djadochtatherium" catopsaloides. Acta Palaeontologica Polonica 39, p.134-136.

Page references: Kielan-Jaworowska Z & Hurum JH (2001), Phylogeny and Systematics of multituberculate mammals. Paleontology 44, p.389-429.
Kielan-Jaworowska Z, Hurum JH, Currie PJ, & Barsbold R (2002), New data on anatomy of the Late Cretaceous multituberculate mammal Catopsbaatar. Acta Palaeontologica Polonica 47(3), p.557-560.

(This information has been derived from [1] MESOZOIC MAMMALS; Djadochtatherioidea, an internet directory. As that's my webpage, there are no issues of copyright. Trevor Dykes)