Xinminbao Group Explained

Xīnmínbǎo Group
新民堡群
Type:Geological formation
Age:Late Barremian-Aptian
Period:Aptian
Prilithology:Conglomerate, siltstone, mudstone
Otherlithology:Sandstone
Region:East Asia
Country:
Subunits:Chijinbao Formation, Digou Formation, Xiagou Formation, Zhonggou Formation

The Xīnmínbǎo 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 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

Ceratopsians

Ceratopsians reported from the Xinminbao Group
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
ArchaeoceratopsArchaeoceratops oshimai"[Two] individuals lacking forelimbs."[1]
AuroraceratopsAuroraceratops rugosus
MicroceratusMicroceratus gobiensis
Microceratus sulcidens
PsittacosaurusPsittacosaurus mazongshanensis"One individual lacking caudal and hindlimb."

Crocodilians

Indeterminate crocodilian remains are known from the group.

Ornithopods

Ornithopods reported from the Xinminbao Group
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
EquijubusEquijubus normani"Skull and partial postcranial skeleton."[2] (both this and Probactrosaurus are properly hadrosauroids rather than hadrosaurids)
Gongpoquansaurus[3] date= (help)Gongpoquansaurus mazongshanensis"Partial skull and postcranial skeleton."[4]
SiluosaurusSiluosaurus zhangqiani"Teeth."[5] Nomen dubium, tentatively classified as a Hypsilophodontid.

Saurischians

Saurischians reported from the Xinminbao Group
GenusSpeciesLocationStratigraphic positionMaterialNotesImages
AsiatosaurusAsiatosaurus mongoliensis
BeishanlongBeishanlong grandisA deinocheirid ornithomimosaur.
ChiayusaurusC. lacustris
GobititanGobititan shenzhouensis
"Nanshiungosaurus""Nanshiungosaurus bohlini""[Sixteen] cervical and dorsal vertebrae."[6] [7] This species does not belong to Nanshiungosaurus.[8]
SinornithoidesIndeterminate

Thyreophorans

Indeterminate ankylosaur remains are known from the group.

Turtles

See also

Further reading

Notes and References

  1. "Table 22.1," in Weishampel, et al. (2004). Page 479.
  2. "Table 19.1," in Weishampel, et al. (2004). Page 415.
  3. H.-l. You et al. (in press). "Gongpoquansaurus mazongshanensis (Lü, 1997) comb. nov. (Ornithischia: Hadrosauroidea) from the Early Cretaceous of Gansu Province, northwestern China". In David A. Eberth and David C. Evans (eds). Hadrosaurs: Proceedings of the International Hadrosaur Symposium. Indiana University Press. . Check date values in:
  4. "Table 19.1," in Weishampel, et al. (2004). Page 417.
  5. "Table 18.1," in Weishampel, et al. (2004). Page 396.
  6. Book: Dong. Z.. You. H.. 1997. Sino-Japanese Silk Road Dinosaur Expedition. A new segnosaur from Mazhongshan Area, Gansu Province, China. Dong. Z. M.. China Ocean Press. Beijing. 90−95.
  7. L. E.. Zanno. 2010. A taxonomic and phylogenetic re-evaluation of Therizinosauria (Dinosauria: Maniraptora). Journal of Systematic Palaeontology. 8. 4. 503−543. 10.1080/14772019.2010.488045. 2010JSPal...8..503Z .
  8. You. H.. Morschhauser. E. M.. Li. D.. Dodson. P.. 2018. Introducing the Mazongshan Dinosaur Fauna. Journal of Vertebrate Paleontology. 38. sup. 1. 1−11. 10.1080/02724634.2017.1396995. 2018JVPal..38S...1Y .