Xiagou Formation

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.

Xiagou Formation
Stratigraphic range: Aptian
~125–113 Ma
TypeGeological formation
Unit ofXinminbao Group
UnderliesZhonggou Formation
OverliesChijinpu Formation
Lithology
PrimaryMudstone
OtherShale, siltstone
Location
Coordinates39.9°N 96.8°E / 39.9; 96.8
Approximate paleocoordinates39.1°N 97.5°E / 39.1; 97.5
RegionGansu
Country China
ExtentChangma Basin
Type section
Named forXiagou
Xiagou Formation (China)

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 middle 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]

Color key
Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon
 Notes
Uncertain or tentative taxa are in small text; crossed out taxa are discredited.

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]

Birds
Genus Species Location Stratigraphic position Material Notes Images
Avimaia[7] A. schweitzerae[7] Changma Basin "Partial skeleton with an egg."[7] An enantiornithean.
Changmaornis[8] C. houi[8] Changma Basin "Partial pelvic girdle with hindlimb."[8] An euornithian.
Dunhuangia[9] D. cuii[9] Changma Basin "Forelimbs."[9] An enantiornithean.
Feitianius[10] F. paradisi[10] Changma Basin "Hindlimbs with pelvic area and vertebrae."[10] An enantiornithean
Gansus[3] G. yumenensis[3] "Partil hindlimbs."[3] An euornithian.
Jiuquanornis[8] J. niui[8] Changma Basin "Partial pectoral girdle."[8] An euornithian.
Qiliania[11] Q. graffini[11] Changma Basin "Partial skeleton from two individuals."[11] An enantiornithean.
Unnamed enantiornithean Indeterminate "Partial forelimb."[12] An enantiornithean.
Yumenornis[8] Y. huangi[8] Changma Basin "Right forelimb."[8] An euornithian.

Ornithomimosaurs
Genus Species Location Stratigraphic position Material Notes Images
Beishanlong[13] B. grandis[13] Yujingzi Basin Gray-variegated beds "Fore and hindlimbs with partial vertebrae."[13] An ornithomimosaur.

Therizinosaurs
Genus Species Location Stratigraphic position Material Notes Images
Suzhousaurus[14] S. megatherioides[14] Yujingzi Basin Gray-variegated beds "Dorsal vertebrae, ribs and partial shoulder girdle."[14] A therizinosauroid.

Tyrannosauroids
Genus Species Location Stratigraphic position Material Notes Images
Xiongguanlong[15] X. baimoensis[15] Yujingzi Basin Gray-variegated beds "Skull without lower jaws, partial vertebrae, ilium and femur."[15] A tyrannosauroid.

Ceratopsians
Genus Species Location Stratigraphic position Material Notes Images
Archaeoceratops[16] A. yujingziensis[17] Yujingzi Basin Gray-variegated beds "Caudal vertebrae and a partial hindlimb."[17] A neoceratopsian.

Hadrosauroids
Genus Species Location Stratigraphic position Material Notes Images
Jintasaurus[18] J. meniscus[18] Yujingzi Basin Gray-variegated beds "Partial skull."[18] A hadrosauroid.
Xuwulong[19] X. yueluni[19] Yujingzi Basin Gray-variegated beds "Articulated skeleton lacking limbs."[19] A hadrosauroid.

Macronarians
Genus Species Location Stratigraphic position Material Notes Images
Qiaowanlong[20] Q. kangxii[20] Yujingzi Basin Gray-variegated beds "Cervical vertebrae and right pelvic girdle."[20] A somphospondylan.

Turtles
Genus Species Location Stratigraphic position Material Notes Images
Changmachelys[21] C. bohlini[21] Changma Basin "Nearly complete skeletons from four individuals."[21] A macrobaenid.

Fish
Genus Species Location Stratigraphic position Material Notes Images
Shuleichthys[22] S. brachypteryx[22] "Complete skeleton from four individuals."[22] An osteoglossomorph.

See also

References
  1. You, Hai-lu; Lamanna, Matthew C.; Harris, Jerald D.; Chiappe, Luis M.; O'Connor, Jingmai; Ji, Shu-an; Lü, Jun-chang; Yuan, Chong-xi; Li; Zhang, Xing; Lacovara, Kenneth J.; Dodson, Peter and Ji, Qiang, Da-qing (2006). "A Nearly Modern Amphibious Bird from the Early Cretaceous of Northwestern China". Science. 312: 1640–1643.CS1 maint: multiple names: authors list (link)
  2. You, H.; Morschhauser, E. M.; Li, D.; Dodson, P. (2018). "Introducing the Mazongshan Dinosaur Fauna". Journal of Vertebrate Paleontology. 38 (sup. 1): 1−11. doi:10.1080/02724634.2017.1396995.
  3. 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. P. Vršanský. 2003. Umenocoleoidea - an amazing lineage of aberrant insects (Insecta, Blattaria). AMBA Projekty 7(1):1-32
  5. 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. Y. C. Hong. 1982. Mesozoic Fossil Insects of Jiuquan Basin in Gansu Province 1-187
  7. Bailleul, Alida M.; et al. (20 March 2019). "An Early Cretaceous enantiornithine (Aves) preserving an unlaid egg and probable medullary bone". Nature Communications. 10 (1275): 1275. Bibcode:2019NatCo..10.1275B. doi:10.1038/s41467-019-09259-x. PMC 6426974. PMID 30894527.
  8. Wang, Y.; O'Connor, J. K.; Li, D.; You, H. (2013). "Previously Unrecognized Ornithuromorph Bird Diversity in the Early Cretaceous Changma Basin, Gansu Province, Northwestern China". PLOS ONE. 8 (10): e77693. Bibcode:2013PLoSO...877693W. doi:10.1371/journal.pone.0077693. PMC 3795672. PMID 24147058.
  9. 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
  10. 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
  11. Ji, Shu-An; Atterholt, Jessie; O'Connor, Jingmai; Lamanna, Matthew; Harris, Jerry; Li, Da-Qing; You, Hai-Lu; Dodson, Peter (2011). "A new, three-dimensionally preserved enantiornithine bird (Aves: Ornithothoraces) from Gansu Province, north-western China". Zoological Journal of the Linnean Society. 162 (1): 201–219. doi:10.1111/j.1096-3642.2010.00671.x.
  12. You et al. 2005 A new fossil bird from the Early Cretaceous of Gansu Province, northwestern China Historical Biology 17(1-4):7-14
  13. Makovicky, Peter J.; Li, Daqing; Gao, Ke-Qin; Lewin, Matthew; Erickson, Gregory M.; Norell, Mark A. (2010). "A giant ornithomimosaur from the Early Cretaceous of China". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 191–198. doi:10.1098/rspb.2009.0236. PMC 2842665. PMID 19386658.
  14. Li, D.; Peng, C.; You, H.; Lamanna, M. C.; Harris, J. D.; Lacovara, K. J.; Zhang, J. (2007). "A Large Therizinosauroid (Dinosauria: Theropoda) from the Early Cretaceous of Northwestern China". Acta Geologica Sinica (English Edition). 81 (4): 539−549. doi:10.1111/j.1755-6724.2007.tb00977.x. ISSN 1000-9515.
  15. Li, Daqing; Norell, Mark A.; Gao, Ke-Qin; Smith, Nathan D.; Makovicky, Peter J. (2009). "A longirostrine tyrannosauroid from the Early Cretaceous of China". Proceedings of the Royal Society B: Biological Sciences. 277 (1679): 183–190. doi:10.1098/rspb.2009.0249. PMC 2842666. PMID 19386654.
  16. Dong, Z.; Azuma, Y. (1997). "On a primitive Neoceratopsian from the early Cretaceous of China". In Dong, Z. (ed.). Sino-Japanese Silk Road dinosaur expedition. China Ocean press. pp. 68–89.
  17. You, Hai-Lu; Tanque, Kyo; Dodson, Peter (2010). "A new species of Archaeoceratops (Dinosauria: Neoceratopsia) from the Early Cretaceous of the Mazongshan area, northwestern China". In Ryan, Michael J.; Chinnery-Allgeier, Brenda J.; Eberth, David A. (eds.). New Perspectives on Horned Dinosaurs: The Royal Tyrrell Museum Ceratopsian Symposium. Bloomington and Indianapolis: Indiana University Press. pp. 59–67. ISBN 978-0-253-35358-0.
  18. Hai-Lu You; Da-Qing Li (2009). "A new basal hadrosauriform dinosaur (Ornithischia: Iguanodontia) from the Early Cretaceous of northwestern China". Canadian Journal of Earth Sciences. 46 (12): 949–957. doi:10.1139/E09-067.
  19. You Hailu, Li Daqing and Liu Weichang (2011). "A New Hadrosauriform Dinosaur from the Early Cretaceous of Gansu Province, China". Acta Geologica Sinica. 85 (1): 51–57. doi:10.1111/j.1755-6724.2011.00377.x.
  20. You, Hai-Lu; Li, Da-Qing (22 November 2009). "The first well-preserved Early Cretaceous brachiosaurid dinosaur in Asia". Proceedings of the Royal Society B: Biological Sciences. 276 (1695): 4077–4082. doi:10.1098/rspb.2009.1278. PMC 2825791. PMID 19734188.
  21. Brinkman, D.B.; Yuan, C.-X.; Ji, Q.; Ji, D.; You, H. (2013). "A new turtle from the Xiagou Formation (Early Cretaceous) of Changma Basin, Gansu Province, P. R. China". Palaeobiodiversity and Palaeoenvironments. 93: 367–382.
  22. 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
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