Xinminbao Group

The Xīnmínbǎo Group (Template:Zh) is a group of geological formations in north central China. They occur across a large depression between the Altai Mountains of Mongolia to the north and the Qilian mountains of the Qinghai Plateau to the south, in the Gōngpóquán (公婆泉) and Suànjǐngzi (算井子) basins, and also in the neighbouring Jiuquan Basin.

Both of these areas are inland basins consisting of fluvial (river), lacustrine (lake), and intermontane (between mountains) alluvial fan (floodplain) sediments that were deposited during the Early Cretaceous, probably during the Aptian or possibly late Barremian stage, when the climate was semi-arid and subtropical.

The group has been visited by many expeditions including the Silk Road dinosaur expedition of 1992 which concentrated on the area around Mazong Shan.

Geology

The group is made up of three main formations.

Chijinbao Formation

This consists of a lower red unit of coarse conglomerates grading to fine sandstones representing river channel to alluvial fan deposits, and an upper unit of red clastic sediments from either overbank deposits in a meandering fluvial environment, or accumulation in a shallow lacustrine or paludal (marsh) environment.

Digou Formation

This consists of grey siltstones and calcareous mudstones comprising two sequences of fluvio-lacustrine sedimentation with some alluvial fan and littoral (lake-shore) deposits.

Zhonggou Formation

This consists of red siltstones and mudstones in a series of upwardly coarsening cycles of lacustrine sediments.

Vertebrate fauna

The dinosaurs of the Xinminbao Group are collectively referred to as the Mazongshan Dinosaur Fauna, representing a unique dinosaur assemblage from all other known dinosaur faunas.

Ceratopsians

Ceratopsians reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Archaeoceratops	Archaeoceratops oshimai			"[Two] individuals lacking forelimbs."		File:Archaeoceratops BW.jpg Archaeoceratops File:Auroraceratops UDL.png Auroraceratops
Auroraceratops	Auroraceratops rugosus
Microceratus	Microceratus gobiensis
	Microceratus sulcidens
Psittacosaurus	Psittacosaurus mazongshanensis			"One individual lacking caudal and hindlimb."

Ornithopods

Ornithopods reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Equijubus	Equijubus normani			"Skull and partial postcranial skeleton."	(both this and Probactrosaurus are properly hadrosauroids rather than hadrosaurids)
Gongpoquansaurus	Gongpoquansaurus mazongshanensis			"Partial skull and postcranial skeleton."
Siluosaurus	Siluosaurus zhangqiani			"Teeth."	Nomen dubium, tentatively classified as a Hypsilophodontid.

Saurischians

Saurischians reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Asiatosaurus	Asiatosaurus mongoliensis					File:Beishanlong grandis.jpg Beishanlong File:Sinornithoides-youngi jconway.png Sinornithoides
Beishanlong	Beishanlong grandis				A deinocheirid ornithomimosaur.
Chiayusaurus	C. lacustris
Gobititan	Gobititan shenzhouensis
"Nanshiungosaurus"	"Nanshiungosaurus bohlini"			"[Sixteen] cervical and dorsal vertebrae."	This species does not belong to Nanshiungosaurus.
Sinornithoides	Indeterminate

Thyreophorans

Indeterminate ankylosaur remains are known from the group.

Thyreophorans of the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Stegosaurides	Stegosaurides excavatus				(nomen dubium)

Crocodilians

Indeterminate crocodilian remains are known from the group.

Crocodilians reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Chiayusuchus	Chiayusuchus cingulatus

Fish

Ray-finned fishes reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Xixiaichthys	Xixiaichthys tongxinensis

Pterosaurs

Pterosaurs reported from the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Material	Notes	Images
Noripterus	Indeterminate					File:Noripterus Clear.jpg Noripterus

Turtles

Turtles of the Xinminbao Group
Genus	Species	Location	Stratigraphic position	Abundance	Notes
Tsaotanemys	Tsaotanemys rugosus

See also

• List of dinosaur-bearing rock formations

Further reading

• A new Psittacosaur (Psittacosaurus mazongshanensis sp. nov.) from Mazongshan area, Ganzu Province. Xu, X. Sino-Japanese Silk Road dinosaur expedition., Dong, Z. (ed). China Ocean press; 48-67 (1997).
• Biostratigraphy and palaeoenvironment of the dinosaur-bearing sediments in Lower Cretaceous of Mazongshan area, Gansu Province, China. Tang, F., Luo, Z., Zhou, Z., You, H., Georgi, J., Tang, Z., and Wang. X. Cretaceous Research 22, 115-129 (2001).