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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 |
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 along with fossils from other invertebrates and vertebrates, which are rare but well-preserved. The slightly younger Panxian biota has a more diverse and common assortment of marine reptiles such as sauropterygians.[1]
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.[2]
Among others, the following fossils were reported from the formation:
Genus | Species | Member/Biota | Notes | Image |
---|---|---|---|---|
Barracudasauroides[3] | B. panxianensis | Upper Member; Panxian biota[3][1] | A small mixosaurid ichthyosaur, either a member of its own genus[4] or a species of Mixosaurus[1]. | |
B. cf. panxianensis | Upper Member; Luoping biota[1] | A small mixosaurid ichthyosaur, simmilar to the slightly younger B. panxianensis. | ||
Phalarodon[5][6] | P. cf. fraasi[5] | Upper Member; Panxian biota[1] | Known from a skull of a small mixosaurid ichthyosaur with durophagous dentition. | |
P. atavus[6] | Upper Member; Luoping biota[1] | A small mixosaurid ichthyosaur known from a complete skeleton. Might represent a member of its own genus, Contectopalatus. | ||
Xinminosaurus[7] | X. catactes | Upper Member; Panxian biota[1] | A medium-sized early ichthyosaur with durophagous dentition, possibly a member of Cymbospondylidae. |
Genus | Species | Member/Biota | Notes | Image |
---|---|---|---|---|
Atopodentatus[8] | A. unicus | Upper Member; Luoping biota[8] | A bizzare, likely herbivorous[9] sauropterygian with possible placodontiform affinities[10], known from several well-preserved specimens. | |
Placodus[11] | P. inexpectatus | Upper Member; Panxian biota[11][1] | A medium-sized placodontid placodont, known from a complete specimen[11]. |
Genus | Species | Member/Biota | Notes | Image |
---|---|---|---|---|
Largocephalosaurus | L. polycarpon[12] | Upper Member; Luoping biota [12][1] | A mid-sized basal saurosphargid sauropterygian. | |
L. qianensis[13] | Upper Member; Panxian biota [13][1] | A mid-sized basal saurosphargid sauropterygian. | ||
Sinosaurosphargis[14] | S. yunguinensis | Upper Member; Luoping and Panxian biota [14][1] | A small armoured saurosphargid sauropterygian. |
Genus | Species | Member/Biota | Note | Image |
---|---|---|---|---|
Panzhousaurus | P. rotundirostris | Upper Member; Panxian biota | A small but robust pachypleurosaur known from several specimens. | |
Dianmeisaurus | D. gracilis | Upper Member; Luoping biota | A small pachypleurosaur known from a complete skeleton. | |
D. mutaensis | Upper Member | A very small pachypleurosaur known froma complete skeleton of a juvenile. | ||
Diandongosaurus | D. acutidentatus | Upper Member; Luoping biota | A small pachypleurosaur known from several complete specimens. | |
D. cf. acutidentatus | Upper Member; Luoping biota | A medium to large sized pachypleurosaur known from a complete pathological skeleton. | ||
Dianopachysaurus | D. dingi | Upper Member; Luoping biota | A small pachypleurosaur known from an immature specimen. | |
Dawazisaurus | D. brevis | Upper Member, Luoping biota | A small pachypleurosaur known from a complete specimen. | |
Honghesaurus | H. longicaudalis | Upper Member, Luoping biota | A gracile, long-tailed small pachypleurosaur known from a complete specimen. | |
Luopingosaurus | L. imparilis | Upper Member, Luoping biota | A gracile, long-snouted small pachypleurosaur. | |
Wumengosaurus | W. delicatomandibularis | Upper Member; Panxian biota | A relatively large, long-snouted pachypleurosaur known from multiple specimens. | |
W. rotundicarpus | Upper Member; Panxian biota | A medium sized, long-snouted pachypleurosaur known froma complete holotype specimen. |
Genus | Species | Member/Biota | Note | Image |
---|---|---|---|---|
Sanchiaosaurus | S. sungi | Lower Member | A small possible basal nothosauroid known from a single partial specimen. | |
Lariosaurus | L. hongguoensis | Upper Member; Panxian biota | Example | |
L. sp. indet. | Upper Member; Luoping biota | Example | ||
Nothosaurus | N. yangjuanensis | Upper Member; Panxian biota | ||
N. rostellatus | Upper member; Panxian biota | Example | ||
N. zhangi | Upper Member; Luoping biota | Example | ||
N. luopingensis | Upper Member, Luoping biota | Example |
Genus | Species | Member/Biota | Note | Image |
---|---|---|---|---|
Chinchenia | C. sungi | Lower Member | A possible small pistosauroid known from fragmentary remains. |
Genus | Species | Member | Note | Image |
---|---|---|---|---|
Luxisaurus[15] | L. terrestris | Upper Member | A small tanystropheid archosauromorph, known from partial limbs. | |
Gracilicollum | G. latens | Upper Member; Panxian biota | A small, long-necked tanystropheid archosauromorph, known from a skull and neck vertebrae. |
Genus | Species | Member | Note | Image |
---|---|---|---|---|
Dinocephalosaurus | D. orientalis | Upper Member; Panxian biota | A large, long-necked dinocephalosaurid archosauromorph, known from several specimens. | |
D. cf. orientalis | Upper Member; Luoping biota | A large, lock-necked dinocephalosaurid archosauromorph, simmilar to the slightly younger D. orientalis. | ||
Pectodens | P. zhenyuensis | Upper Member; Luoping biota | A small, long limbed dinocephalosaurid archosauromorph, known from a complete specimen. | |
Austronaga[16] | A. minuta | Upper Member; Luoping biota | A small dinocephalosaurid archosauromorph, known from a partial skeleton. |
Genus | Species | Member | Note | Image |
---|---|---|---|---|
Qianosuchus | Q. mixtus | Upper Member; Panxian biota | A medium-sized poposauroid pseudosuchian with semi-aquatic adaptations. | |
cf. Qianosuchus | cf. Q. sp. indet. | Upper Member; Luoping biota | A taxon known primarily from teeth. |
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