''Yubaatar'' is a

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

multituberculate Multituberculata (commonly known as multituberculates, named for the multiple tubercles of their teeth) is an extinct order of rodent-like mammals with a fossil record spanning over 130 million years. They first appeared in the Middle Jurassic, a ...

, an extinct order of rodent-like

mammals A mammal () is a vertebrate animal of the class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three middle e ...

, which lived in what is now

China China, officially the People's Republic of China (PRC), is a country in East Asia. With population of China, a population exceeding 1.4 billion, it is the list of countries by population (United Nations), second-most populous country after ...

during the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''cre ...

. The first specimen was discovered in the

Qiupa Formation The Qiupa Formation () is a Late Cretaceous Maastrichtian geologic formation in Henan Province, central China. It is rich in dinosaur eggs and bones, such as those of carnivorous and herbivorous dinosaurs. The Qiupa Formation is considered to be ...

Luanchuan County Luanchuan County () is a county under the jurisdiction of the prefecture-level city of Luoyang, in the west of Henan province, China. It has an area of and a population of 318,000. The county contains significant deposits of molybdenum and tungs ...

, in the

Henan Province Henan; alternatively Honan is a province in Central China. Henan is home to many heritage sites, including Yinxu, the ruins of the final capital of the Shang dynasty () and the Shaolin Temple. Four of the historical capitals of China, Luo ...

. The specimen consists of a partial skeleton with a nearly complete skull, and was made the

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

of the new genus and species ''Yubaartar zhongyuanensis'' by the Chinese palaeontologist Li Xu and colleagues in 2015. The generic name consists of the word ''Yu'', which is the

pinyin Hanyu Pinyin, or simply pinyin, officially the Chinese Phonetic Alphabet, is the most common romanization system for Standard Chinese. ''Hanyu'' () literally means 'Han Chinese, Han language'—that is, the Chinese language—while ''pinyin' ...

spelling of the

Chinese character Chinese characters are logographs used to write the Chinese languages and others from regions historically influenced by Chinese culture. Of the four independently invented writing systems accepted by scholars, they represent the only on ...

for the Henan Province, and the Mongolian word ''baatar'', which means "hero", a word commonly used as suffix in the names of Asian multituberculates. The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

comes from

Zhongyuan Zhongyuan (), the Central Plain(s), also known as Zhongtu (, lit. 'central land') and Zhongzhou (, lit. 'central region'), commonly refers to the part of the North China Plain surrounding the lower and middle reaches of the Yellow River, centere ...

, an ancient name for the geographic area of the province. Yubaatar skull

''Yubaatar'' is the first known and southernmost Late Cretaceous multituberculate outside of the Mongolian plateau (most multituberculate specimens mainly consist only of teeth and jaws, and are rarely found in eastern Asia). With a skull 7 cm long, ''Yubaatar'' was one of the largest members of the group known from the

Mesozoic The Mesozoic Era is the Era (geology), era of Earth's Geologic time scale, geological history, lasting from about , comprising the Triassic, Jurassic and Cretaceous Period (geology), Periods. It is characterized by the dominance of archosaurian r ...

, only exceeded in size by '' Erythrobaatar'' and ''

Bubodens ''Bubodens magnus'' is a poorly understood, extinct multituberculate mammal from the Upper Cretaceous of South Dakota. It is known only from a single tooth, and has uncertain placement within the suborder Cimolodonta though has been tentatively a ...

''. ''Yubaatar'' had a unique feature among multituberculates in that its last 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 ...

was replaced. The holotype specimen had a

palaeopathology Paleopathology, also spelled palaeopathology, is the study of ancient diseases and injuries in organisms through the examination of fossils, mummified tissue, skeletal remains, and analysis of coprolites. Specific sources in the study of ancient ...

unique among known

mammal, a severely broken right

tibia The tibia (; : tibiae or tibias), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two Leg bones, bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outsi ...

bone, which was probably damaged in an accident, but had healed. ''Yubaatar'' was found to be basal to the

clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

Taeniolabidoidea Taeniolabidoidea is a group of extinct mammals known whose fossils can be found in North America and Asia. They were the largest members of the extinct order Multituberculata, as well as the largest non-therian mammals. '' Lambdopsalis'' even pr ...

, which consists of North American and Asian multituberculates; this indicates there was a faunal interchange between Asia and North America before the Cretaceous–Paleogene transition. The morphology of ''Yubaatar'' indicates that diversity in the complexity of the teeth of multituberculates, relating to their diets, increased with the number of genera and difference in body size, and that there was a shift in adaptations towards increased herbivory in the group across the Cretaceous–Paleogene boundary. Yubaatar zhongyuanensis

References

{{Taxonbar, from=Q24056613 Cretaceous mammals Cimolodonta Fossil taxa described in 2015 Fossils of China Prehistoric mammal genera