Catopsbaatar
Catopsbaatar is a genus of multituberculate, an extinct order of rodent-like mammals. It lived in what is now Mongolia during the late Campanian age of the Late Cretaceous Period, about 72 million years ago. The first fossils were collected in the early 1970s, and the animal was named as a new species of the genus "Djadochtatherium " in 1974, "D. catopsaloides". The specific name refers to the animal's similarity to the genus "Catopsalis". The species was moved to the genus "Catopsalis" in 1979, and received its own genus ("Catopsbaatar", Greek and Mongolian for "visible hero") in 1994. Five skulls, one molar, and one skeleton with a skull are known; the latter is the genus' most complete specimen. "Catopsbaatar" was a member of the family Djadochtatheriidae.
Catopsbaatar
The skull of "Catopsbaatar" was heavy-set, with a wide margin across the front. It was shorter along the midline than at the sides, because the nuchal crest at the back of the head curved inwards at the middle, creating an indention at the hind margin of the skull when viewed from above. The zygomatic arches were strongly expanded to the sides, with the skull width (across the arches) about 85 percent of the skull length. The front of the orbits (eye sockets) were further back than in other djadochtatheriids, resulting in a more elongated snout (65 percent of the skull length) and small orbits. The premaxilla (front bone of the upper jaw) extended less than two-thirds of the length of the snout in front of the eyes, shorter than that of "Kryptobaatar". The premaxilla consisted of parts of the face and the palate; djadochtatheriids had a premaxillary ridge on the boundary between the two (visible when viewing the skull from below). The palatal part of the premaxilla was concave, with many randomly arranged nutrient foramina (openings). The nasal bone—which formed the upper part of the snout—was relatively wide (becoming wider towards the back), and its front was covered with irregularly spaced vascular foramina. The suture between the nasal and frontal bones was less pointed forwards in the middle than were those of "Catopsbaatar"'s relatives. 
The maxilla (the main part of the upper jaw) was extensive, and formed most of the side of the snout. It contained all the upper teeth, except the incisors. The infraorbital foramina (openings at the lower front of the maxilla) were slit-like in some specimens and rounded in others, and varied in number from one to three. One of the most characteristic features of the face of "Catopsbaatar" was the very large anterior zygomatic ridge on the sides of the upper jaw (a site for jaw-muscle attachment). It was much higher than in other djadochtatheriids except for "Djadochtatherium", from which it differed in that the ridge was semicircular rather than roughly trapezoidal (other genera have elliptical ridges). The front margin of the anterior zygomatic ridge was thickened, which produced a bulge on the side margin of the snout when viewed from the side and above. The lower part of the suture between the maxilla and the squamosal bone extended along the hind border of the anterior zygomatic ridge. The palatal processes of the maxilla formed most of the palate. The major palatine foramina had shallow grooves extending forward. The postpalatine torus (a bony protrusion on the palate) of "Catopsbaatar" was less prominent than was that of "Tombaatar". The frontal bone was large, and formed most of the cranial roof. The suture between the frontal and parietal bones formed a U-shaped part in the middle which pointed backwards—similar to the condition in "Kryptobaatar" but less deep, with smaller U-shaped structures at the sides. This differed from "Djadochtatherium", which had a narrower V-shaped suture between the frontal and parietal bones.
The intermediate zygomatic ridge on the squamosal bone (also for jaw-muscle attachment) was much smaller and lower than the anterior zygomatic ridge in front of it. "Catopsbaatar" differed from other djadochtatheriids in that the intermediate ridge contacted the anterior ridge with its front edge. The posterior zygomatic ridge at the lower back of the squamosal bone was the weakest of the three ridges, and only marked by a depression. The postorbital processes behind the orbit on the parietal bone were very long, and the parietal ridges extended from the hind margin of the postorbital processes towards each other (but without reaching). The nuchal crest was very prominent, and extended to the sides to form "wings". The occipital plate was almost vertical and slightly concave, and was obscured by the nuchal crest when the skull was viewed from above. Though incompletely preserved, it is assumed that the occipital plate sloped back and upwards from the occipital condyles (as in some relatives). The orbito-temporal vascular system inside the skull of "Catopsbaatar" did not differ much from those of related genera.