Xinminbao Group

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The Xinminbao Group 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 Gonpoquan and Suanjingze 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.

Contents 1 Geology 1.1 Chijinbao Formation 1.2 Digou Formation 1.3 Zhonggou Formation 2 Fossil taxa 2.1 Osteichthyes (bony fish ) 2.2 Testudines (turtles) 2.3 Crocodilians (crocodiles) 2.4 Pterosaurs 2.5 Dinosaurs 2.5.1 Ankylosaurs 2.5.2 Ceratopsians 2.5.3 Ornithopods 2.5.4 Hadrosaurs 2.5.5 Sauropods 2.5.6 Theropods 3 References

[edit] Geology

The Group is made up of three main formations.

[edit] 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.

[edit] 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.

[edit] Zhonggou Formation

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

[edit] Fossil taxa

Fossils found in the Xinminbao Group include:

[edit] Osteichthyes (bony fish )

• Xixiaichthys tongxinensis

[edit] Testudines (turtles)

• Tsaotanemys rugosus

[edit] Crocodilians (crocodiles)

• Chiayusuchus cingulatus
• Indeterminate crocodilian

[edit] Pterosaurs

• Noripterus sp.

[edit] Dinosaurs

[edit] Ankylosaurs

• Heishansaurus pachycephalus (nomen dubium - originally described as, and may be, a pachycephalosaur)
• Stegosaurides excavatus (nomen dubium)
• Indeterminate ankylosaurid

[edit] Ceratopsians

• Archaeoceratops oshimai
• Auroraceratops rugosus
• Microceratus gobiensis
• M. sulcidens
• Psittacosaurus mazongshanensis

[edit] Ornithopods

• Siluosaurus zhangqiani (nomen dubium, tentatively classified as a Hypsilophodontid)

[edit] Hadrosaurs

• Equijubus normani (both this and Probactrosaurus are properly hadrosauroids rather than hadrosaurids)
• Probactrosaurus mazongshanensis

[edit] Sauropods

• Asiatosaurus mongoliensis (nomen dubium)
• Chiayusaurus sp.
• Gobititan shenzhouensis
• Indeterminate nemegtosaur

[edit] Theropods

• Nanshiungosaurus bohlini (this species may not belong in Nanshiungosaurus)
• Sinornithoides sp.
• Indeterminate allosaur
• Indeterminate dromaeosaur
• Indeterminate ornithomimid
• Indeterminate theropod

[edit] References

• 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).