Guanling Formation
Geological formation in China From Wikipedia, the free encyclopedia
The Guanling Formation is a Middle Triassic (Anisian or Pelsonian in the regional chronostratigraphy) geologic formation in southwestern China.
| Guanling Formation | |
|---|---|
| Stratigraphic range: early-mid Anisian (Pelsonian) ~ | |
| Type | Geological formation |
| Underlies | Yangliujing Formation |
| Overlies | Jialingjiang Formation |
| Lithology | |
| Primary | Mudstone, limestone |
| Other | Dolomite |
| Location | |
| Coordinates | 25.5°N 104.9°E |
| Approximate paleocoordinates | 11.7°N 94.2°E |
| Region | Guizhou & Yunnan Provinces |
| Country | China |
| Extent | Yunnan–Guizhou Plateau |
 Guanling Formation (China)  Guanling Formation (Guizhou) | |
Geology
The formation encompasses two members. The first member is primarily calcareous mudstone and dolomite, indicative of a coastal environment. The second member is a thicker marine sequence of dark micritic limestone with some dolomite. Two distinct fossil assemblages are found in the second member. The older Luoping biota preserves abundant arthropods (including isopods,[1] decapods,[2] mysidaceans and thylacocephalans[3]) along with fossils from other invertebrates and vertebrates, which are rare but well-preserved. The slightly younger Panxian fauna has a more diverse and common assortment of marine reptiles such as sauropterygians.[4]
A tuff bed in the Luoping biota has been dated to 244.5 ± 2.2 Ma via U-Pb SHRIMP dating. The Luoping biota as a whole was deposited over a period of 340 ± 71 kyr. This estimate is justified by cyclostratigraphic evidence, as indicated by fluctuations of terrestrial proxy metals.[5]
Fossil content
Summarize
Perspective
Among others, the following fossils were reported from the formation:
Ichthyopterygia
| Genus | Species | Member | Notes | Image |
|---|---|---|---|---|
| Barracudasauroides[6] | B. panxianensis | Upper Member[6][4] | A small mixosaurid ichthyosaur, either a member of its own genus[7] or a species of Mixosaurus.[4] | |
| Phalarodon[8][9] | P. cf. fraasi[8] | Upper Member[4] | Known from a skull of a small mixosaurid ichthyosaur with durophagous dentition. | |
| P. atavus[9] | Upper Member[4] | A small mixosaurid ichthyosaur known from a complete skeleton. Might represent a member of its own genus, Contectopalatus. | ||
| Xinminosaurus[10] | X. catactes | Upper Member[4] | A medium-sized early ichthyosaur with durophagous dentition, possibly a member of Cymbospondylidae. |
Sauropterygia
| Genus | Species | Member | Notes | Image |
|---|---|---|---|---|
| Atopodentatus[11] | A. unicus | Upper Member[11] | A bizarre, likely herbivorous[12] sauropterygian with possible placodontiform affinities,[13] known from several well-preserved specimens. | |
| Placodus[14] | P. inexpectatus | Upper Member[14][4] | A medium-sized placodontid placodont, known from a complete specimen.[14] |
| Genus | Species | Member | Notes | Image |
|---|---|---|---|---|
| Largocephalosaurus | L. polycarpon[15] | Upper Member [15][4] | A mid-sized basal saurosphargid sauropterygian. | |
| L. qianensis[16] | Upper Member [16][4] | A mid-sized basal saurosphargid sauropterygian. | ||
| Sinosaurosphargis[17] | S. yunguinensis | Upper Member [17][4] | A small armoured saurosphargid sauropterygian. |
- Altisolepis
- Austronaga[18]
- Dawazisaurus
- Diandongichthys[19]
- Diandongosaurus
- Diandongperleidus
- Dianopachysaurus
- Dianmeisaurus
- Dinocephalosaurus[20]
- Feroxichthys
- Frodoichthys
- Gimlichthys
- Gracilicollum
- Honghesaurus
- Kyphosichthys
- Luopingcoelacanthus
- Luopingosaurus[21]
- Luopingperleidus
- Luoxiongichthys
- Luxisaurus[20]
- Mixosaurus
- Nothosaurus
- Panxianichthys
- Pectodens[20]
- Platysiagum
- Pteronisculus
- Qianosuchus
- Sanchiaosaurus
- Sangiorgioichthys
- Saurichthys
- Sinosaurichthys
- Trachelosaurus
- Venusichthys
- Wumengosaurus
- Yelangichthys
- Yudaiichthys
- Yunnancoelacanthus
References
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