''Morrisonodon brentbaatar'' is an extinct multituberculate mammal from the

Upper Jurassic The Late Jurassic is the third epoch of the Jurassic Period, and it spans the geologic time from 161.5 ± 1.0 to 143.1 ± 0.8 million years ago (Ma), which is preserved in Upper Jurassic strata.Owen 1987. In European lithostratigraphy, the name ...

Morrison Formation The Morrison Formation is a distinctive sequence of Upper Jurassic sedimentary rock found in the western United States which has been the most fertile source of dinosaur fossils in North America. It is composed of mudstone, sandstone, siltston ...

of North America. ''M. brentbaatar'' was described by Robert T. Bakker in 1998, who originally placed it in the genus ''

Ctenacodon ''Ctenacodon'' is a genus of extinct mammal that lived in what is now North America during the Upper Jurassic period. It is a member of the family Allodontidae within the order Multituberculata. ''Ctenacodon'', also known as ''Allodon'' (Marsh 1 ...

''. The fossil remains consist of a jaw fragment containing two upper

premolar The premolars, also called premolar Tooth (human), teeth, or bicuspids, are transitional teeth located between the Canine tooth, canine and Molar (tooth), molar teeth. In humans, there are two premolars per dental terminology#Quadrant, quadrant in ...

s and the sockets corresponding to two molars. The remains were found in the Upper Jurassic

Wyoming Wyoming ( ) is a landlocked U.S. state, state in the Mountain states, Mountain West subregion of the Western United States, Western United States. It borders Montana to the north and northwest, South Dakota and Nebraska to the east, Idaho t ...

. The species name honours the Wyoming paleontologist Brent Breithaupt, while "Baatar" is a Mongolian for "hero". Bakker assigned his specimens to ''Ctenacodon'' with hesitation, noting additional specimens may require a new classification. In a 2001 review of multituberculates,

Zofia Kielan-Jaworowska Zofia Emilia Kielan-Jaworowska (25 April 1925 – 13 March 2015) was a Polish paleobiologist. In the mid-1960s, she led a series of Polish-Mongolian paleontological expeditions to the Gobi Desert. She was the first woman to serve on the executi ...

and

Jørn Hurum Jørn Harald Hurum (born November 4, 1967) is a Norway, Norwegian paleontologist and popularizer of science. He is a vertebrate paleontologist and holds an associate professor position at the Natural History Museum at the University of Oslo, Natur ...

did not recognize Bakker's specimen as related to other ''Ctenacodon'' species or even belonging to the family

Allodontidae Allodontidae (from ancient Greek "ἄλλος" "ὀδούς", "different tooth") is a family of extinct multituberculate mammal that lived in what is now North America during the Upper Jurassic period. They were relatively early mammals and are ...

, speculating the species might instead belong to the family

Plagiaulacidae Plagiaulacidae is a family of fossil mammals within the order Multituberculata. Remains are known from the Upper Jurassic and earliest Cretaceous of North America and Europe. They were among the more derived representatives of the informal subord ...

. In 2004, the species was placed in the newly established genus ''Morrisonodon''.

References

Multituberculata Morrison mammals Fossil taxa described in 2004 Prehistoric mammal genera {{jurassic-mammal-stub