Xiagou Formation

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Template:Short description Template:Infobox rockunit

The Xiagou Formation is the middle strata of the Xinminbao Group. It is named for its type site in Xiagou, in the Changma Basin of Gansu Province, northwestern China and is considered Early Cretaceous in age. It is known outside the specialized world of Chinese geology as the site of a Lagerstätte in which the fossils were preserved of Gansus yumenensis, the earliest true modern bird.

Description

The laminated yellowish mudstones of the Xiagou Formation are the lithified remnants of varves that were laid down as extremely fine silt settled to the bottom of a tranquil freshwater lake. The result was dense anoxic bottom sediment, where the lack of bacteria slowed the processes of decay, preserving uncompressed fossils in details that include feather impressions and remnants of the webbing between the bird's toes. The age of the formation has not yet been confidently determined. The underlying Chijinpu Formation is likely the same age as the Jehol Group due to the presence of similar fossils, meaning that the Xiagou Formation is probably slightly younger than the Jehol biota, dating to around the late Aptian.[1][2]

Fossil content

The Xiagou Formation is particularly noted for its high diversity of ancient birds. These include both modern birds close to the ancestors of living species, and related lineages now entirely extinct. Other fossils from the Xiagou Formation are characteristic of an Early Cretaceous lake ecology. There are fossils of abundant fish fauna, Charophyta and ostracods.[3] Template:Paleobiota-key-compact

Invertebrates

Arthropods

Genus Species Location Stratigraphic position Material Notes Images
Blattapterix[4] B. gansu[4]
Cretacechorista[5] C. qilianshanensis[5]
Eurycoleus[6] E. arcuatus, E. clypeolatus, E. dimorphocellatus, E. parvus[6] A carabid.
Glottocoleus[6] G. lenticulata, G. stellatus[6]
Mesoblattina[6] M. cretacea[6]
Mesocoleus[6] M. zhonggouense[6]
Mesotricupes[6] M. reticulatus[6]
Petalocupes[6] P. arcus[6]
Phyllocoleus[6] P. striolatus[6]
Planocoleus[6] P. ensatus[6]
Pleurocoleus[6] P. catenatus[6]
Spinus[6] S. yumenense[6]
Tetillopsis[6] T. parvula[6]
Yumenocoleus[6] Y. intermedius, Y. lineatus, Y. longus[6]

Theropods

Birds

Genus Species Location Stratigraphic position Material Notes Images
Avimaia[7] A. schweitzerae[7] Changma Basin "Partial skeleton with an egg."[7] An enantiornithean.
File:Fossil-AvimaiaSchweitzerae-PhotoPartialSkeleton-LineDrawing.png
Brevidentavis[8] B. zhangi[8] Incomplete skull and cervical vertebrae.[8] An ornithuromorph.
Changmaornis[9] C. houi[9] Changma Basin "Partial pelvic girdle with hindlimb."[9] An euornithian.
Dunhuangia[10] D. cuii[10] Changma Basin "Forelimbs."[10] An enantiornithean.
Feitianius[11] F. paradisi[11] Changma Basin "Hindlimbs with pelvic area and vertebrae."[11] An enantiornithean.
File:Feitianius paradisi.jpg
Gansus[3] G. yumenensis[3] "Partial hindlimbs."[3] An euornithian.
File:Gansus zheni - early cretaceous Liaoning IMG 5188 Beijing Museum of Natural History.jpg
Jiuquanornis[9] J. niui[9] Changma Basin "Partial pectoral girdle."[9] An euornithian.
Meemannavis[8] M. ductrix[8] Incomplete skull and cervical and thoracic vertebrae.[8] An ornithuromorph.
Novavis[12] N. pubisculata[12] Changma Basin Partial skeleton including tail vertebrae, a pelvis, and the hindlimbs.[12] An enantiornithean.
Qiliania[13] Q. graffini[13] Changma Basin "Partial skeleton from two individuals."[13] An enantiornithean.
Unnamed enantiornithean Indeterminate "Partial forelimb."[14] An enantiornithean.
Yumenornis[9] Y. huangi[9] Changma Basin "Right forelimb."[9] An euornithian.

Ornithomimosaurs

Genus Species Location Stratigraphic position Material Notes Images
Beishanlong[15] B. grandis[15] Yujingzi Basin Gray-variegated beds "Fore and hindlimbs with partial vertebrae."[15] An ornithomimosaur.
File:Beishanlong grandis.jpg

Therizinosaurs

Genus Species Location Stratigraphic position Material Notes Images
Suzhousaurus[16] S. megatherioides[16] Yujingzi Basin Gray-variegated beds "Dorsal vertebrae, ribs and partial shoulder girdle."[16] A therizinosauroid.
File:Suzhousaurus.JPG

Tyrannosauroids

Genus Species Location Stratigraphic position Material Notes Images
Xiongguanlong[17] X. baimoensis[17] Yujingzi Basin Gray-variegated beds "Skull without lower jaws, partial vertebrae, ilium and femur."[17] A tyrannosauroid.
File:Xiongguanlong NT.jpg

Cerapods

Ceratopsians

Genus Species Location Stratigraphic position Material Notes Images
Archaeoceratops[18] A. yujingziensis[19] Yujingzi Basin Gray-variegated beds "Caudal vertebrae and a partial hindlimb."[19] A neoceratopsian.
File:Archaeoceratops NT.jpg

Hadrosauroids

Genus Species Location Stratigraphic position Material Notes Images
Jintasaurus[20] J. meniscus[20] Yujingzi Basin Gray-variegated beds "Partial skull."[20] A hadrosauroid.
Xuwulong[21] X. yueluni[21] Yujingzi Basin Gray-variegated beds "Articulated skeleton lacking limbs."[21] A hadrosauroid.
File:Xuwulong NT.jpg

Sauropods

Macronarians

Genus Species Location Stratigraphic position Material Notes Images
Qiaowanlong[22] Q. kangxii[22] Yujingzi Basin Gray-variegated beds "Cervical vertebrae and right pelvic girdle."[22] A somphospondylan.
File:Qiaowanlong NT.jpg

Other vertebrates

Turtles

Genus Species Location Stratigraphic position Material Notes Images
Changmachelys[23] C. bohlini[23] Changma Basin "Nearly complete skeletons from four individuals."[23] A macrobaenid.

Fish

Genus Species Location Stratigraphic position Material Notes Images
Shuleichthys[24] S. brachypteryx[24] "Complete skeleton from four individuals."[24] An osteoglossomorph.

Plants

Genus Species Location Stratigraphic member Material Notes Images
Xenoxylon[25] X. meisteri Hongliuxia Wood A podocarp

See also

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References

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  1. ↑ Script error: No such module "Citation/CS1".
  2. ↑ Script error: No such module "Citation/CS1".
  3. ↑ a b c d L. Hou and Z. Liu. 1984. A new fossil bird from Lower Cretaceous of Gansu and early evolution of birds. Scientia Sinica, series B 27(12):1296-1301
  4. ↑ a b P. Vršanský. 2003. Umenocoleoidea - an amazing lineage of aberrant insects (Insecta, Blattaria). AMBA Projekty 7(1):1-32
  5. ↑ a b Y. C. Hong, D. S. Yan, and D. R. Wang. 1989. Discovery of Early Cretaceous Cretacechorista gen. nov. Insecta: Mecoptera from Jiuquan basin Gansu Province. Memoirs of Beijing Natural History Museum 44:1-9
  6. ↑ a b c d e f g h i j k l m n o p q r s t u v w x Y. C. Hong. 1982. Mesozoic Fossil Insects of Jiuquan Basin in Gansu Province 1-187
  7. ↑ a b c Script error: No such module "Citation/CS1".
  8. ↑ a b c d e f Script error: No such module "Citation/CS1".
  9. ↑ a b c d e f g h i Script error: No such module "Citation/CS1".
  10. ↑ a b c M. Wang, D. Li, J. K. O'Connor, Z. Zhou and H. You. 2015. "Second species of enantiornithine bird from the Lower Cretaceous Changma Basin, northwestern China with implications for the taxonomic diversity of the Changma avifauna". Cretaceous Research 55: 56-65
  11. ↑ a b c O’Connor, J. K., D.-Q. Li, M. C. Lamanna, M. Wang, J. D. Harris, J. Atterholt, and H.-L. You. 2015. "A new Early Cretaceous enantiornithine (Aves, Ornithothoraces) from northwestern China with elaborate tail ornamentation". Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054035 https://www.tandfonline.com/doi/abs/10.1080/02724634.2015.1054035?journalCode=ujvp20
  12. ↑ a b c Script error: No such module "Citation/CS1".
  13. ↑ a b c Script error: No such module "Citation/CS1".
  14. ↑ You et al. 2005 A new fossil bird from the Early Cretaceous of Gansu Province, northwestern China Historical Biology 17(1-4):7-14
  15. ↑ a b c Script error: No such module "Citation/CS1".
  16. ↑ a b c Script error: No such module "Citation/CS1".
  17. ↑ a b c Script error: No such module "Citation/CS1".
  18. ↑ Script error: No such module "citation/CS1".
  19. ↑ a b Script error: No such module "citation/CS1".
  20. ↑ a b c Script error: No such module "Citation/CS1".
  21. ↑ a b c Script error: No such module "Citation/CS1".
  22. ↑ a b c Script error: No such module "Citation/CS1".
  23. ↑ a b c Script error: No such module "Citation/CS1".
  24. ↑ a b c A. M. Murray, H. L. You, and C. Peng. 2010. A New Cretaceous Osteoglossomorph Fish from Gansu Province, China. Journal of Vertebrate Paleontology 30(2):322-332
  25. ↑ Script error: No such module "Citation/CS1".
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