Xijun Ni

• Ph.D.
• Professor (Full) at Chinese Academy of Sciences

Plain Language Summary The Paleocene–Eocene Thermal Maximum (PETM), which occurred approximately 56 million years ago, was a period of extreme global warming. The PETM has been linked to large amounts of light carbon entering the ocean–atmosphere system. Wildfires that burned peatland during this period may have been a source of light carbon. Model...

The Anthropocene's human-dominated habitat expansion endangers global biodiversity. However, large mammalian herbivores experienced few extinctions during the 20th century, hinting at potentially overlooked ecological responses of a group sensitive to global change. Using dental microwear as a proxy, we studied large herbivore dietary niches over a...

We report a new genus and species of Entelodontidae, Entelodontellus zhouliangi gen. et sp. nov. The new taxon is represented by a pair of mandibular halves which belong to the same individual. The left mandible preserves three molars and the right half preserves p4–m3. It can be distinguished from other entelodonts by presenting a large robust pos...

The partial skeleton of a fossil snake is described from the Upper Miocene “Liushu” Formation of the Linxia Basin, Gansu Province, in the northeastern Tibetan Plateau of China. Material preserves rare cranial materials of the palatomaxillary arch, in addition to a series of vertebrae, represents a new species of erycine sand boa, Eryx linxiaensis s...

Yuomys are medium-sized Hystricomorpha rodents. They are known for coming from areas of low elevation in China during the middle and late Eocene. Two new Yuomys were discovered from a locality near Xueshuo village in Litang County, Sichuan Province. The locality lies in the Gemusi pull-apart basin formed in the Litang Fault System (LTFS) in the Hen...

Fossil evidence is indispensable for studying the derivation, divergence, and dispersal of squirrels as they responded to global Cenozoic climatic and paleoenvironmental change. Among these fossil records, the earliest known definitive fossil squirrels in Eurasia occur after the Eocene/Oligocene Boundary and are slightly younger than the oldest rec...

Cranial endocasts are one of the most direct tools available to obtain information about the endocranial cavity of fossil mammals, but few anatomical comparisons have analyzed endocranial data within a phylogenetic framework. Our study combines analyses of new digital endocasts from high-resolution X-ray micro-computed tomography (µCT) for two noto...

The oldest‐known undoubted cultural practices of intentional cranial deformation (ICD, also known as artificial cranial modification) appeared in the Middle East, Australia and Northeast China in the terminal Pleistocene‐early Holocene populations. Here we report an ICD calvarium fossil (Songhuajiang II) discovered from an underwater sand mining si...

A latest Paleocene charophyte flora collected from the South Gobi area in the Junggar Basin, western China, includes the geographically widespread taxa Peckichara torulosa var. varians (Dollfus and Fritel, 1919) Sanjuan, Vicente, and Eaton, 2020, Lychnothmanus vectensis (Groves, 1926) Soulié-Märsche, 1989, and Gyrogona lemani capitata Grambast and...

A new species, Yuomys robustus of the ctenodactyloid rodent Yuomys, is described in the paper. It is from the Western margin of the Ordos Basin District in eastern Ningxia Hui Autonomous Region, China. Yuomys robustus is characterized by a combination of features: large size, high tooth crown, having a postparacrista on M2 and lacking hypocone on P...

Bats dispersed widely after evolving the capacity for powered flight, and fossil bats are known from the early Eocene of most continents. Until now, however, bats have been conspicuously absent from the early Eocene of mainland Asia. Here, we report two teeth from the Junggar Basin of northern Xinjiang, China belonging to the first known early Eoce...

As one of the most complete archaic human fossils, the Harbin cranium provides critical evidence for studying the diversification of the Homo genus and the origin of Homo sapiens. However, the unsystematic recovery of this cranium and a long and confused history since the discovery impede its accurate dating. Here, we carried out a series of geoche...

It has recently become clear that several human lineages coexisted with Homo sapiens during the late Middle and Late Pleistocene. Here, we report an archaic human fossil that throws new light on debates concerning the diversification of the Homo genus and the origin of H. sapiens. The fossil was recovered in Harbin city in northeastern China, with...

Here we report a new cricetid s.l., Caecocricetodon yani, gen. et sp. nov., discovered in the early Oligocene of the Caijiachong Formation in Yunnan Province, China. The new cricetid differs from all known cricetids or stem muroids by its particular molar pattern displaying numerous crests and spurs. Our phylogenetic analysis based on a matrix incl...

Neogene strata rich in fossil mammals are well exposed in central Nei Mongol, China. Over a dozen mammalian faunas in chronological succession from Early Miocene to Early Pliocene were discerned in this region, and they built a fundamental part of the Neogene land mammal biochronological system in northern China. Tuchengzi was first recognized for...

The “giant” beaver, Trogontherium cuvieri Fischer, 1809, is an extinct species that was widely distributed from the late Pliocene to the late Pleistocene all over the Palaearctic Realm. The global environment during this period is characterized by periodic and extreme climate changes, and most mammalian groups experienced rapid evolution during thi...

The dire wolf was one of the successful top predators in North America during the Pleistocene. It is best known from the southern part of North America, and it even immigrated to South America. Fossils of dire wolves are very rare north of 42° North latitude in North America. That distribution supported the belief that the low temperatures and ice...

Bovid material from Xishuigou, Tabenbuluk area, Gansu Province, China, is described here. The type material of ‘Eotragus’ halamagaiensis from the Halamagai Formation, Junggar Basin, Xinjiang Uygur Autonomous Region, China is reviewed as well. Both should be attributed to Turcocerus halamagaiensis comb. nov. The short and almost straight horn cores...

New fossil remains of order artiodactyla have been recovered from Dhok Pathan Formation, northern Pakistan. The assemblage represents 16 specimens belonging to seven species of order artiodactyla which are Selenoportax vexillarius, Pachyportax latidens, Dorcatherium minus, Dorcatherium majus, Gazella lydekkeri, Hippopotamodon sivalense and Propotam...

Hereditary hierarchy is one of the major features of complex societies. Without a written record, prehistoric evidence for hereditary hierarchy is rare. Intentional cranial deformation (ICD) is a ritualized and cross-generational cultural practice that embodies social identity and cultural beliefs in adults through the behavior of permanently and i...

Remains of platacanthomyids from Leilao, a late Miocene hominoid locality in Yuanmou, Yunnan, China are described. Five species in three genera are recognized: Neocometes sp., Platacanthomys dianensis Qiu, 1989, Typhlomys aff. T . primitivus Qiu, 1989, T. hipparionum Qiu, 1989 and T . storchi n. sp. Leilao is the only locality that produces fossils...

We report 7 mammalian and 16 pollen species from the top of the Shimagou Formation in Kumkol Basin of northern Qinghai-Xizang Plateau, whose age is latest Middle Miocene (about 12.5 Ma). We erect a new species of fossil rodent, Spermophilinus kumkolensis sp. nov. The micromammalian fauna from the Kumkol Basin shares high similarities with contempor...

Mammals are the most important elements in Cenozoic terrestrial ecosystem. The composition and the character of a mammalian fauna are controlled by evolution time and evolutionary rate. Here we took 50 Asian Paleogene mammalian faunas as representatives and applied Bayesian Tip-dating method to infer the relationships and divergence times among the...

Understanding of ancestral conditions for anthropoids has been hampered by the paucity of well-preserved early fossils. Here, we provide an unprecedented view of the cerebral morphology of the 20-million-year-old Chilecebus carrascoensis , the best-preserved early diverging platyrrhine known, obtained via high-resolution CT scanning and 3D digital...

As one of the three major groups of gomphotheres, the Miocene Choerolophodontidae were long considered to have been distributed in Europe, Africa, and South Asia, with a few localities in East Asia, whereas choerolophodontids never extended into North America during the Miocene. In this paper, we report new Choerolophodon fossil materials from the...

The “giant” beaver, Trogontherium cuvieri Fischer, 1809, is an extinct species that was widely distributed all over Palaearctic Realm. And the well-approved temporal range of this species is from the Late Pliocene to Middle Pleistocene. Here we report a new specimen of T. cuvieri from the upper Pleistocene of the Songhua River drainage area near Ha...

Hereditary hierarchy is one of the major features of complex societies. Without a written record, prehistoric evidence for hereditary hierarchy is rare. Intentional cranial deformation (ICD) is a cross-generational cultural practice that embodies social identity and culture beliefs in adults through the behavior of altering infant head shape. There...

Background: Tamquammys has been considered one of the basal ctenodactyloid rodents, which has been documented in the earliest to middle Eocene (~ 56.0-48.5 Ma) in China. It was the most abundant and widespread rodent genus in the Erlian Basin (Nei Mongol, China) and dominated Arshantan small-mammal faunas of that region. Here for the first time we...

Early Eocene bats are known from Africa, Australia, Europe, North and South America, and India. The oldest species date to ~55 million years and are known only from isolated teeth and jaw fragments. Slightly younger fossils from the early and middle Eocene include preserved postcrania of at least six stem families. The absence of early Eocene bats...

Two new species of fossil hamsters (Cricetinae, Cricetidae) collected from early Pliocene sediments (∼4.4 Ma) in the Zanda Basin, southwestern Tibet (China), demonstrate greater past diversity among cricetines in the hinterland of the Tibetan Plateau within the Himalayan Range (beyond the previously known ‘Plesiodipus’ thibetensis from the late Mio...

Here, we describe hundreds of isolated phalanges attributed to middle Eocene fossil primates from the Shanghuang fissure-fillings from southern Jiangsu Province, China. Extending knowledge based on previous descriptions of postcranial material from Shanghuang, this sample of primate finger and toe bones includes proximal phalanges, middle phalanges...

The Early to Late Oligocene Propalaeocastor is the earliest known beaver genus from Eurasia. Although many species of this genus have been described, these species are defined based on very fragmentary specimens. Propalaeocastor irtyshensis from the Early Oligocene Irtysh River Formation in northwestern Xinjiang, China is one of the earliest-known...

Data matrix used for phylogenetic analysis The data matrix was edited in Mesquite v3.2 software (Maddison & Maddison, 2017) and saved in the NEXUS format.

Relatived references to the taxa in the data matrix for phylogenetic analysis

The Early to Late Oligocene Propalaeocastor is the earliest known beaver genus from Eurasia. Although many species of this genus have been described, these species are defined based on very fragmentary specimens. Propalaeocastor irtyshensis from the Early Oligocene Irtysh River Formation in northwestern Xinjiang, China is one of the earliest-known...

The Early to Late Oligocene Propalaeocastor is the earliest known beaver genus from Eurasia. Although many species of this genus have been described, these species are defined based on very fragmentary specimens. Propalaeocastor irtyshensis from the Early Oligocene Irtysh River Formation in northwestern Xinjiang, China is one of the earliest-known...

Obtaining accurate estimations of the body mass of fossil primates has always been a subject of interest in paleoanthropology because mass is an important determinant for so many other aspects of biology, ecology, and life history. This paper focuses on the issues involved in attempting to reconstruct the mass of two early Eocene haplorhine primate...

Deltatheroidans are primitive metatherian mammals (relatives of marsupials), previously thought to have become extinct during the Cretaceous mass extinction. Here, we report a tiny new deltatheroidan mammal (Gurbanodelta kara gen. et sp. nov.) discovered at the South Gobi locality in China (Xinjiang Province) that is the first Cenozoic record of th...

Os Notoungulata incluem a maior parte da diversidade dos grupos de ungulados nativos extintos Sul-Americanos, com mais de 150 gêneros distribuídos em cerca de 14 famílias. No entanto, o grupo é relativamente pouco explorado do ponto de vista filogenético. O presente estudo combina dados de descrições anatômicas prévias e exame direto de espécimes p...

Mylagaulid fossorial rodents are a common component of North American Miocene fossil faunas. However outside of North America, only three species are known from Asia. Here we report two new mylagaulids, Irtyshogaulus minor gen. et sp. nov. and Irtyshogaulus major gen. et sp. nov., recovered from early Miocene sediments in the Junggar Basin in north...

Irtyshogaulus minor left M1 (IVPP V 20328) xy rotation. (MOV)

Irtyshogaulus minor left m2 (IVPP V 20329.14) xy rotation. (MOV)

Irtyshogaulus minor left m2 (IVPP V 20329.14) xz rotation. (MOV)

Irtyshogaulus major right M1 (IVPP V 20809) xz rotation. (MOV)

Irtyshogaulus minor left m2 (IVPP V 20329.14) cut. (MOV)

Data matrix used in phylogenetic analysis in TNT format. (TXT)

Irtyshogaulus minor left M1 (IVPP V 20328) cut. (MOV)

Irtyshogaulus major right M1 (IVPP V 20809) xy rotation. (MOV)

Irtyshogaulus major right M1 (IVPP V 20809) cut. (MOV)

Irtyshogaulus major right m2 (IVPP V 20810.6) cut. (MOV)

Irtyshogaulus minor left M1 (IVPP V 20328) xz rotation. (MOV)

Majority and strict consensus trees in NEXUS format. (TXT)

Irtyshogaulus major right m2 (IVPP V 20810.6) xy rotation. (MOV)

Irtyshogaulus major right m2 (IVPP V 20810.6) xz rotation. (MOV)

New fossils pertaining to the oldest known Asian plesiadapiform, the Gashatan carpolestid Subengius mengi, clarify aspects of the dental anatomy of this taxon. The dentition of S. mengi is substantially more primitive than previously recognized in retaining a lower dental formula of 2.1.3.3, a low-crowned p4 with three main cusps that are less full...

The muroid Cricetops Matthew and Granger, 1923 commonly occurred in the Oligocene terrestrial deposits in central and northern Asia. Here we report the first record of Cricetops in the southern part of Asia. Isolated rodent molars named as a new species, Cricetops auster sp. nov., were discovered from the early Oligocene sediments at the Lijiawa lo...

Climate filters dominant species The transition between the Eocene and Oligocene periods was marked by distinct cooling. Because primate species are particularly susceptible to cold, this change in climate drove a retraction of primates globally. After this transition, anthropoid primates were dominant in Afro-Arabian regions, but little has been k...

Treeshrews are widely considered a "living model" of an ancestral primate, and have long been called "living fossils". Actual fossils of treeshrews, however, are extremely rare. We report a new fossil species of Ptilocercus treeshrew recovered from the early Oligocene (~34 Ma) of China that represents the oldest definitive fossil record of the crow...

The Tibetan Plateau (TP) is a regional Earth system showing very strong interactions among its lithosphere, hydrosphere, cryosphere, biosphere, atmosphere, and anthrosphere. These interactions manifest TP's impact on surrounding regions and reflect TP's response to the global change. Quantifying the multispherical interactions is critically importa...

The endocranium of notoungulates, a largely endemic group of extinct South American herbivorous mammals, has been studied through artificial and natural cranial endocasts, and more recently via digital endocasts. Although previous works provide descriptive anatomical and volume data on notoungulate endocasts that permit comparative studies on relat...

The endocranium of notoungulates, a largely endemic group of extinct South American herbivorous mammals, has been studied through artificial and natural cranial endocasts, and more recently via digital endocasts. Although previous works provide descriptive anatomical and volume data on notoungulate endocasts that permit comparative studies on relat...

Seven primate distal phalanges have been identified from two middle Eocene fossil localities (Locality 1 and Nanbaotou) in the Yuanqu Basin, China, providing the first evidence of distal phalangeal morphology in Asian Eocene adapiform and eosimiid primates. The bones are best allocated to the basal anthropoid Eosimias centennicus and to hoanghoniin...

The transition in the evolution of cetaceans from terrestrial life to a fully aquatic existence is one of the most enduring evolutionary mysteries. Stem cetaceans are quite diverse and well documented in the fossil record. Five family level clades form the paraphyletic stem cetaceans ('archaeocetes'): Pakicetidae, Ambulocetidae, Remingtonocetidae,...

An avian coracoid from the early Pleistocene Qigequan Formation in the Qaidam Basin, Qinghai Province, China, in the northern part of the Qinghai-Tibetan Plateau represents one of the few avian fossils from the region. The specimen is from an individual of a shelduck (Tadorna sp.), and its phylogenetic position is supported by the presence of a pro...

The Eocene–Oligocene Boundary (,34 million years ago) marks one of the largest extinctions of marine invertebrates in the world oceans and of mammalian fauna in Europe and Asia in the Cenozoic era. A shift to a cooler climate across this boundary has been suggested as the cause of this extinction in the marine environment, but there is no manifold...

Microtoid cricetids are widely considered to be the ancestral form of arvicoline rodents, a successful rodent group including voles, lemmings and muskrats. The earliest previously known microtoid cricetid is Microtocricetus molassicus Fahlbusch and Mayr 1975 from the MN9 (about 10-11 Ma) of Europe. Here we report a new microtoid cricetid, Primopris...

Mammalian bipedalism has long been thought to have arisen in response to arid and open environments. Here we tested whether bipedalism coevolved with environmental changes using molecular and paleontological data from the rodent superfamily Dipodoidea and statistical methods for reconstructing ancestral characteristics and past climates. Our result...

Two new avian fossils from the Late Eocene of Xinjiang in western China appear to document the possible first occurrence of the extinct anseriform group Romainvilliinae (Anatidae) within China and Asia. The tarsometatarsus has several anseriform and anatid characters, and a combination of traits only reported from the romainvilliines among waterfow...

The labyrinth of vertebrate inner ear contains the organs responsible for the senses of hearing and equilibrium. Research on the morphology and function of this delicate structure has a very long history. In recent years, the sophisticated high resolution X-ray computed tomography has been widely applied in the research on the labyrinth of fossil v...

The phylogenetic relationships of notoungulates, an extinct group of predominantly South American herbivores, remain poorly resolved with respect to both other placental mammals and among one another. Most previous phylogenetic analyses of notoungulates have not included characters of the internal cranium, not least because few such features, inclu...

Among the 14small mammal species from the early Miocene locality of the northern area of the Junggar basin (northern Xinjiang, China), four species are cricetids (Rodentia): unnamed species of Cricetodon and Eumyarion, and two new species, Karydomys debruijni nov. sp. and Megacricetodon beijiangensis nov. sp. Some aspects of the morphology of Crice...

Tree-building with diverse data maximizes explanatory power. Application of molecular clock models to ancient speciation events risks a bias against detection of fast radiations subsequent to the Cretaceous-Paleogene (K-Pg) event. Contrary to Springer et al., post–K-Pg placental diversification does not require “virus-like” substitution rates. Even...

Reconstructing the earliest phases of primate evolution has been impeded by gaps in the fossil record, so that disagreements persist regarding the palaeobiology and phylogenetic relationships of the earliest primates. Here we report the discovery of a nearly complete and partly articulated skeleton of a primitive haplorhine primate from the early E...

This chapter reviews works surrounding the Chinese land mammal age (CLMA), with particular focus on the stratigraphic data from the Xiejia locality and Junggar Basin. It considers the possibilities that the Xiejia fauna may represent a subunit of the Late Oligocene Tabenbulukian and that a new biochronologic unit, the Suosuoquanian, may be used to...

To discover interordinal relationships of living and fossil placental mammals and the time of origin of placentals relative to the Cretaceous-Paleogene (K-Pg) boundary, we scored 4541 phenomic characters de novo for 86 fossil and living species. Combining these data with molecular sequences, we obtained a phylogenetic tree that, when calibrated wit...