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. 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. 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.
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]
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[edit] Fossil taxa
Fossils found in the Yixian Formation include:
[edit] Dinosaurs (including birds)
- Sinosauropteryx, the first feathered nonavian dinosaur found here (compsognathid)
- Huaxiagnathus (compsognathid)
- Sinocalliopteryx (compsognathid)
- Beipiaosaurus (therizinosaur)
- Caudipteryx (oviraptorosaur)
- Incisivosaurus (oviraptorosaur)
- Protarchaeopteryx (oviraptorosaur)
- Dilong (tyrannosauroid)
- Mei (deinonychosaur) - a small dinosaur that has been fossilized in a sleeping position, with its head tucked under one arm
- Microraptor (deinonychosaur)
- Sinovenator (deinonychosaur)
- Sinornithosaurus (deinonychosaur)
- Shenzhousaurus (ornithomimosaur)
- Shenzhouraptor AKA Jeholornis (avian: basal bird)
- "Liaoxiornis" (avian? A nomen dubium)
- Sapeornis (avian: omnivoropterygiform)
- Confuciusornis (avian: basal pygostylian)
- Jinzhouornis (avian: basal pygostylian) - possibly a junior synonym of Confuciusornis
- Sinornis/Cathayornis (avian: enantiornithine)
- Longipteryx (avian: enantiornithine?)
- Liaoningornis (avian: liaoningornithiform)
- Archaeorhynchus (avian: Ornithurae)
- Paraprotopteryx" (avian: enantiornithine)
- Liaoceratops (ceratopsian)
- Psittacosaurus (ceratopsian)
- Jeholosaurus (ornithopod)
- Jinzhousaurus (ornithopod)
[edit] Pterosaurs
[edit] Mammals
- Jeholodens
- Repenomamus, which ate small dinosaurs
- Yanoconodon
Metatheria (marsupials)
Eutheria (placental mammals)
[edit] Other vertebrates
- Dalinghosaurus, a lizard
- Xianglong, a gliding lizard
- Yabeinosaurus, a lizard related to geckos and skinks
- Hyphalosaurus
- Monjurosuchus
- Manchurochelys
- Jeholotriton, a gilled salamander
- Callobatrachus, a frog
- Mesophryne, a frog with no known living relatives
- Peipiaosteus, a fish related to sturgeons
- Lycoptera, herring-like fish
- Sinamia
- Mesomyzon mengae, a fossil lamprey
[edit] Insects and other arthropods
- giant water strider bug
- Jehol crayfish
- Orb-weaving spider
- Mayfly
- Carrion-eating beetles
- Cicada
- Dragonfly
- Cockroach
- Palaepangonius, an early pollinating fly
[edit] Plants
- Archaefructus
- Horsetail
- Ephedra
- Conifer trees
- Ginkgo trees
- Archaeamphora, the earliest known carnivorous plant
[edit] See also
- List of fossil sites (with link directory)
[edit] References
- ^ 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.
