Yixian Formation

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The Yixian Formation is a geological formation in Jinzhou, Liaoning, People's Republic of China, that stems from the early Cretaceous period. It is known for its fossils.

Contents

History

Japanese occupation

It was initially recognized during the time the Japanese Empire controlled a large chunk of Manchuria (Northern China) called "Jehol". During the occupation of Jehol, many Japanese scientists had noticed fossil remains of extinct fish and reptiles, possibly the champsosaurs. These initial fossil discoveries made by Japanese scientists vanished from history once World War II ended in 1945.

Chinese rediscovery

By 1949, when administration of the area passed to the Communist Party and its leader Mao Zedong, the fossils of Yixian were studied only by Chinese scientists. It was not until the 1990s when remarkable fossils of birds and dinosaurs were excavated. Since 1996, a number of dinosaur fossils that have revolutionized knowledge of these animals have been found at Yixian; among them are the first known non-avian theropods with feathers. See Jehol Biota.

Dating

For some time, the formation was believed to be from the Late Jurassic-Early Cretaceous boundary, some 145 mya (million years ago). Radiometric dating has since resolved it to be younger; it is now considered to have been deposited in the Barremian to early Aptian, some 125-121 mya.1

The Yixian Formation forms the lowest part of the Jehol group, defined by Gu (1962 and 1983) as a group of geological formations including the Jehol Coal-bearing Beds, the Jehol Oil Shale Beds, and the Jehol Volcanic Rocks.2 The Yixian Formation is preceded by the older Daohugou Beds, of uncertain Jurassic or Early Cretaceous age, which are sometimes considered part of the Jehol group. The Yixian Formation (including the Jingangshan, Tuhulu, Jianchang, Lower Volcanic and Volcanic Rock formations) is followed stratigraphically by the slightly younger Jiufotang Formation and the Fuxin Formation.3 Chiappe et al. argued in 1999 that the oldest beds of the Yixian (those bearing a fauna dominated by confuciusornithid birds) were best separated as a distinct formation, called the Chaomidianzi Formation, with a type locality at the village of Sihetun, approximately 25 km south of Beipiao City.4 However, this classification has fallen out of favor, and the Chaomidianzi Formation is disused as a synonym of the Jianshangou Bed of the Yixian Formation.5

Vertebrate fauna of the Yixian Formation

Amphibians

Amphibians of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Callobatrachus sanyanensis
 A frog.

Genus:

  1. Jeholotriton paradoxus
 A gilled salamander.

Genus:

  1. Liaobatrachus grabaui
 A frog.

Genus:

  1. Liaoxitriton zhongjiani
 A salamander related to the earlier L. daohugouensis of the Daohugou Beds.

Genus:

  1. Mesophryne beipiaoensis
 A frog with no known living relatives.

Birds and other theropods

Theropod dinosaurs of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Archaeorhynchus spathula
 An early, advanced short-tailed bird (ornithuran).
Beipiaosaurus
Caudipteryx
Confuciusornis
Huaxiagnathus
Liaoxiornis
Mei long
Sinornis
Sinornithosaurus
Sinosauropteryx

Genus:

  1. Beipiaosaurus inexpectus

From the Jianshangou Beds.6

 A therizinosaur.

Genus:

  1. Caudipteryx dongi
  2. Caudipteryx zoui
  1. From the Jianshangou Beds.6
  2. Common, but only over a small region of the Jianshangou Beds.6

Genus:

  1. Confuciusornis sanctus
  1. From the Jianshangou Beds, where it is extremely common (several hundred specimens).6
 A primitive short-tailed bird (pygostylian).

Genus:

  1. Dilong paradoxus

Rare in both the Lujiatun and Jianshangou Beds.6

 A tyrannosauroid.

Genus:

  1. Graciliraptor lujiatunensis
  1. Rare in the Lujiatun Beds.6

A dromaeosaurid.

Genus:

  1. Huaxiagnathus orientalis
 A compsognathid.6

Genus:

  1. Incisivosaurus gauthieri

Rare in the Lujiatun Beds.6

 An oviraptorosaur.

Genus:

  1. Jinzhouornis yixianensis
  2. Jinzhouornis zhangjiyingia
  1. (Placeholder).
  2. Possible synonym of J. yixianensis.

Genus:

  1. Liaoningornis longidigitris
 A liaoningornithiform ornithuran.

Genus:

  1. Liaoxiornis delicatus
 An entantiornithine.

Genus:

  1. Mei long

From the Lujiatun Beds.6

 A small troodontid fossilized in a sleeping position.

Genus:

  1. Paraprotopteryx gracilis
 An enantiornithine.

Genus:

  1. Protarchaeopteryx robusta

From the Jianshangou Beds.6

A possible relative of Incisivosaurus.

Genus:

  1. Shenzhousaurus orientalis

From the Lujiatun Beds.6

 A primitive ornithomimosaur.

Genus:

  1. Sinocalliopteryx gigas
 A large compsognathid.

Genus:

  1. Sinornithosaurus haoiana
  2. Sinornithosaurus millenii
  1. (Placeholder)
  2. From the Jianshangou Beds.6
  • A dromaeosaurid, the first ever found with feather impressions.

Genus:

  1. Sinosauropteryx prima

From the Jianshangou and Dawangzhangzi Beds.6

 The first feathered non-avian dinosaur found, a compsognathid.

Genus:

  1. Sinovenator changii

Extremely common in the Lujiatun Beds, where literally hundreds of specimens have been recovered.6

A troodontid.

Genus:

  1. Sinusonasus magnodens

From the Lujiatun Beds.6

 A troodontid.

Genus:

  1. Yixianosaurus longimanus

From the Dawangzhangzi Beds.6

 A basal maniraptoran.

Genus:

  1. Zhongornis haoae
 A primitive avian with a short but non-pygostylian tail.

Choristoderans

Choristoderans of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Hyphalosaurus lingyuanensis
Hyphalosaurus

Genus:

  1. Monjurosuchus splendens

Fish

Fish of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Lycoptera davidi
 An osteoglossiform.
Lycoptera

Genus:

  1. Mesomyzon mengae
 A lamprey.

Genus:

  1. Peipiaosteus pani
 A fish related to sturgeons.

Genus:

  1. Sinamia zdanskyi
 A Bowfin.

Lepidosaurians

Lepidosaurian lizards of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Dalinghosaurus longidigitus
 A lizard.
Xianglong

Genus:

  1. Xianglong zhaoi
 A gliding lizard.

Genus:

  1. Yabeinosaurus tenuis
 A lizard related to geckos and skinks.

Mammals

Mammals of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Akidolestes cifellii
 A symmetrodont.7
Gobiconodon
Eomaia
Jeholodens
Repenomamus
Sinodelphys
Yanoconodon
Zhangheotherium

Genus:

  1. Eomaia scansoria
 An early placental mammal.7

Genus:

  1. Gobiconodon zofiae
 A triconodont.7

Genus:

  1. Jeholodens jenkinsi
 A triconodont.7

Genus:

  1. Maotherium sinensis
 A symmetrodont.7

Genus:

  1. Meemannodon lujiatunensis
 A multituberculate.7

Genus:

  1. Repenomamus giganticus
  2. Repenomamus robustus
  • A tricondodont.7
  1. (Placeholder).
  2. A tricondodont, which ate small dinosaurs.

Genus:

  1. Sinobaatar lingyuanensis
 A multituberculate.7

Genus:

  1. Sinodelphys szalayi
 A marsupial.7

Genus:

  1. Yanoconodon allini
 A tricondodont.7

Genus:

  1. Zhangheotherium quinquecuspidens
 A symmetrodont.7

Ornithischians

Ornithischian dinosaurs of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Hongshanosaurus houi
 A ceratopsian.6
Hongshanosaurus
Jeholosaurus
Jinzhousaurus
Liaoceratops
Psittacosaurus

Genus:

  1. Jeholosaurus shangyuanensis
  1. From the Lujiatun Beds.6
 An ornithopod.

Genus:

  1. Jinzhousaurus yangi
  1. From the Dawangzhangzi Beds.6
 An ornithopod.

Genus:

  1. Liaoceratops yanzigouensis
  1. From the Lujiatun Beds.6
 A ceratopsian.

Genus:

  1. Liaoningosaurus paradoxus
  1. From the Dawangzhangzi Beds.6
 A small ankylosaur.

Genus:

  1. Psittacosaurus lujiatunensis
  2. Psittacosaurus major
  3. Psittacosaurus sp.
  • Literally thousands of specimens have been recovered from the Lujiatun Beds. Psittacosaurus is also abundant, although somewhat less common, in the Jianshangou Beds.6

A ceratopsian.

Pterosaurs

Pterosaurs of the Yixian Formation
Taxa Presence Notes Images

Genus:

  1. Beipiaopterus chenianus
 A ctenochasmatid.8

Genus:

  1. Boreopterus cuiae
 A boreopterid.8

Genus:

  1. Cathayopterus grabaui
 A ctenochasmatid.8

Genus:

  1. Dendrorhynchoides curvidentatus
 An anurognathid.8

Genus:

  1. Eosipterus yangi
 A ctenochasmatid.8

Genus:

  1. Feilongus youngi
 A boreopterid.8

Genus:

  1. Haopterus gracilis
 An ornithocheirid.8

Sauropods

Sauropod dinosaurs of the Yixian Formation
Taxa Presence Notes Images

Unranked:

  1. Titanosaur sp.
  1. From the Lujiatun and Jianshangou Beds, fragmentary remains.6
  • One or more species of titanosaur has been recovered from the Yixian Formation.

Turtles

Turtles of the Yixian Formation
Taxa Presence Notes Images

Genus:
Manchurochelys

Invertebrate fauna of the Yixian Formation

Fossil of Archaefructus, an extinct genus aquatic plants, found at the Yixian Formation.

Flora of the Yixian Formation

See also

References

  1. ^ Swisher, Carl C., Wang, Yuan-qing, Wang, Xiao-lin, Xu, Xing, Wang, Yuan. (1999). "Creatceous age for the feathered dinosaurs of Liaoning, China". Nature 400:58-61 1 July 1999.
  2. ^ Gu, Z.W. (1983) "On the boundary of non-marine Jurassic and Cretaceous in China" in: "Nanjing Institute of Geology and Paleontology, Academica Sinica" "Stratigraphical Chart in China with Explanatory Text" Science Press, Beijing 1983:65-82.
  3. ^ Sha, Jingeng. (2007) "Cretaceous Stratigraphy of northeast China: non-marine and marine correlation" Cretaceous Research 28(2) pp.146-170April 2007
  4. ^ Chiappe, L.M., Ji, S.A., Ji, Q., and Norell, M.A. (1999). "Anatomy and systematics of the Confuciusornithidae (Aves) from the Mesozoic of North-eastern China." Bulletin of the American Museum of Natural History, 1999.
  5. ^ Chen, P., Q. Wang, H. Zhang, M. Cao, W. Li, S. Wu, and Y. Shen. (2005). "Jianshangou Bed of the Yixian Formation in west Liaoning, China." Science in China Series D - Earth Sciences, 48: 298-312. doi: 10.1360/04yd0038
  6. ^ a b c d e f g h i j k l m n o p q r s t u v w Xu, X. and Norell, M.A. (2006). "Non-Avian dinosaur fossils from the Lower Cretaceous Jehol Group of western Liaoning, China."Geological Journal, 41: 419-437.
  7. ^ a b c d e f g h i j k Meng, J., Hu, Y., Li, C. and Wang, Y. (2006). "The mammal fauna in the Early Cretaceous Jehol Biota: implications for diversity and biology of Mesozoic mammals."Geological Journal, 41: 439-463.
  8. ^ a b c d e f g Wang, X. and Zhou, Z. (2006). "Pterosaur assemblages of the Jehol Biota and their implication for the Early Cretaceous pterosaur radiation ."Geological Journal, 41: 405-418.
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