The Guanling Formation is a

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma ...

(

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Trias ...

or Pelsonian in the regional chronostratigraphy) geologic

formation Formation may refer to: Linguistics * Back-formation, the process of creating a new lexeme by removing or affixes * Word formation, the creation of a new word by adding affixes Mathematics and science * Cave formation or speleothem, a secondary ...

in southwestern China.

Description

The formation encompasses two members. The first member is primarily

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines. In zoology ''Calcareous'' is used as an a ...

mudstone and dolomite, indicative of a coastal environment. The second member is a thicker marine sequence of dark micritic

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms wh ...

with some dolomite. Two distinct fossil assemblages are found in the second member. The older Luoping biota preserves abundant

arthropods Arthropods (, (gen. ποδός)) are invertebrate animals with an exoskeleton, a segmented body, and paired jointed appendages. Arthropods form the phylum Arthropoda. They are distinguished by their jointed limbs and cuticle made of chitin, oft ...

along with fossils from other

invertebrate Invertebrates are a paraphyletic group of animals that neither possess nor develop a vertebral column (commonly known as a ''backbone'' or ''spine''), derived from the notochord. This is a grouping including all animals apart from the chordate ...

s and

vertebrate Vertebrates () comprise all animal taxon, taxa within the subphylum Vertebrata () (chordates with vertebral column, backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the ...

s, which are rare but well-preserved. The slightly younger Panxian fauna has a more diverse and common assortment of marine reptiles such as

sauropterygia Sauropterygia ("lizard flippers") is an extinct taxon of diverse, aquatic reptiles that developed from terrestrial ancestors soon after the end-Permian extinction and flourished during the Triassic before all except for the Plesiosauria bec ...

ns.

Fossil content

Among others, the following fossils were reported from the formation: * '' Atopodentatus'' * '' Barracudasauroides'' * '' Diandongosaurus'' * '' Dianopachysaurus'' * '' Honghesaurus'' * '' Kyphosichthys'' * '' Largocephalosaurus'' * '' Luopingosaurus'' * '' Luoxiongichthys'' * '' Mixosaurus'' * ''

Qianosuchus ''Qianosuchus'' is an extinct genus of aquatic poposauroid archosaur from the middle Triassic (Anisian) Guanling Formation of Pan County, China. It is represented by two nearly complete skeletons and a crushed skull preserved in the limestone ...

'' * '' Sanchiaosaurus'' * ''

Sinosaurichthys ''Sinosaurichthys'' is an extinct genus of saurichthyid ray-finned fish, which existed in southwestern China during the Middle Triassic (Anisian age). Fossils have been found in the Upper Member of the Guanling Formation of two localities: Y ...

'' * '' Sinosaurosphargis'' * '' Wumengosaurus'' * ''

Xinminosaurus ''Xinminosaurus'' is an extinct genus of cymbospondylid ichthyosaur known from the Middle Triassic (mid-late Anisian stage) of Guizhou Province, China. Etymology The generic name is derived from ''Xinmin'', the district where the fossil was fo ...

References

{{reflist Geologic formations of China Triassic System of Asia Triassic China Limestone formations Dolomite formations Mudstone formations Lagoonal deposits Deep marine deposits Open marine deposits Shallow marine deposits