The Bayan Mandahu Formation (also known as Wulansuhai Formation or Wuliangsuhai Formation) is a

geological Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other E ...

unit of "redbeds" located near the village of Bayan Mandahu in

Inner Mongolia Inner Mongolia, officially the Inner Mongolia Autonomous Region, is an autonomous region of the People's Republic of China. Its border includes most of the length of China's border with the country of Mongolia. Inner Mongolia also accounts for a ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's List of countries and dependencies by population, most populous country, with a Population of China, population exceeding 1.4 billion, slig ...

Asia Asia (, ) is one of the world's most notable geographical regions, which is either considered a continent in its own right or a subcontinent of Eurasia, which shares the continental landmass of Afro-Eurasia with Africa. Asia covers an are ...

(

Gobi Desert The Gobi Desert ( Chinese: 戈壁 (沙漠), Mongolian: Говь (ᠭᠣᠪᠢ)) () is a large desert or brushland region in East Asia, and is the sixth largest desert in the world. Geography The Gobi measures from southwest to northeast a ...

) and dates from the late

Cretaceous The Cretaceous ( ) is a geological period that lasted from about 145 to 66 million years ago (Mya). It is the third and final period of the Mesozoic Era, as well as the longest. At around 79 million years, it is the longest geological period of ...

Period. Laid down in the

Campanian The Campanian is the fifth of six ages of the Late Cretaceous Epoch on the geologic timescale of the International Commission on Stratigraphy (ICS). In chronostratigraphy, it is the fifth of six stages in the Upper Cretaceous Series. Campani ...

, it is dated somewhat uncertainly to between 75 and 71 mya (

million years ago The abbreviation Myr, "million years", is a unit of a quantity of (i.e. ) years, or 31.556926 teraseconds. Usage Myr (million years) is in common use in fields such as Earth science and cosmology. Myr is also used with Mya (million years ago ...

Description

The paleoenvironment it preserves was semi-

arid A region is arid when it severely lacks available water, to the extent of hindering or preventing the growth and development of plant and animal life. Regions with arid climates tend to lack vegetation and are called xeric or desertic. Most ...

and characterized by

alluvial Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. ...

(stream-deposited) and eolian (wind-deposited) sediments. The formation is known for its

vertebrate Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with ...

fossils, most of which are preserved in unstructured sandstone, indicating burial by wind-blown sandstorms.

Paleofauna of the Bayan Mandahu Formation

The

fauna Fauna is all of the animal life present in a particular region or time. The corresponding term for plants is '' flora'', and for fungi, it is '' funga''. Flora, fauna, funga and other forms of life are collectively referred to as '' biota''. ...

of the Bayan Mandahu is very similar in composition to the nearby Djadochta Formation, and the two may have been deposited at roughly the same time. These two formations share many of the same

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

, but differ in the makeup of

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

. For example, the most common mammal in the Djadochta is ''

Kryptobaatar dashzevegi ''Kryptobaatar''and also known as ''Gobibaatar'' or ''Tugrigbaatar'' is an extinct mammalian genus dating from the Upper Cretaceous Period and identified in Central Asia. This animal was a member of the extinct order of Multituberculata within ...

'', while in the Bayan Mandahu, it is the closely related ''

Kryptobaatar mandahuensis ''Kryptobaatar''and also known as ''Gobibaatar'' or ''Tugrigbaatar'' is an extinct mammalian genus dating from the Upper Cretaceous Period and identified in Central Asia. This animal was a member of the extinct order of Multituberculata within ...

''. Similarly, the dinosaur fauna of the Djadochta includes '' Protoceratops andrewsi'' and '' Velociraptor mongoliensis'', while the Bayan Mandahu contains ''

Protoceratops hellenikorhinus ''Protoceratops'' (; ) is a genus of small protoceratopsid dinosaurs that lived in Asia during the Late Cretaceous, around 75 to 71 million years ago. The genus ''Protoceratops'' includes two species: ''P. andrewsi'' and the larger ''P. helleni ...

'' and ''

Velociraptor osmolskae ''Velociraptor'' (; ) is a genus of small dromaeosaurid dinosaur that lived in Asia during the Late Cretaceous epoch, about 75 million to 71 million years ago. Two species are currently recognized, although others have been assigned in the pa ...

''.

Crocodylomorphs

Lizards

amphisbaenia Amphisbaenia (called amphisbaenians or worm lizards) is a group of usually legless squamates, comprising over 200 extant species. Amphisbaenians are characterized by their long bodies, the reduction or loss of the limbs, and rudimentary eyes. As ...

n species is known from the formation. An

iguania Iguania is an infraorder of squamate reptiles that includes iguanas, chameleons, agamids, and New World lizards like anoles and phrynosomatids. Using morphological features as a guide to evolutionary relationships, the Iguania are believed ...

n species is known from the formation.

Turtles

Mammals

A taeniolabidoidea multituberculate is known from the formation.

Dinosaurs

Alvarezsaurs

Ankylosaurs

Birds

Ceratopsians

Dromaeosaurs

Hadrosaurs

Oviraptorosaurs

Sauropods

Troodontids

Tyrannosaurs

References

Bibliography

* {{coord missing, Inner Mongolia Geologic formations of China Upper Cretaceous Series of Asia Campanian Stage Sandstone formations Aeolian deposits Fossiliferous stratigraphic units of Asia Paleontology in Inner Mongolia