The Kaili Formation () is a stratigraphic formation which was deposited during the Lower and Middle Cambrian (~513 to 506 million years ago). The formation is approximately thick and was named after the city Kaili in the Guizhou province of southwest China.
The depositional environment of the Kaili Formation is not entirely known, and there are two hypotheses for its formation. It may have been a nearshore marine environment with 'normal' levels of oxygenation; or it may have been a deeper water environment further from the shore, on the open continental shelf; in this setting oxygen would not be available below the surface layers of the deposited sediment. The trace fossil assemblages in the formation suggest that it was below the wave base and was reasonably well-oxygenated.
Fossils The faunal assemblage is highly diverse, comprising some 110 genera among 11 phyla; of these, some 40 genera are also found in the Burgess Shale, and some 30 are also found in the Maotianshan Shale. Trilobites and eocrinoids with hard parts that are easily preserved are the most common fossils, but many animals with only soft tissues are also preserved. For example, the arthropod Skania similar to the Ediacaran Parvancorina of the Neoproterozoic age Ediacara Hills of South Australia has been found at the Kaili site.
The middle part of the Kaili Formation, the Oryctocephalus indicus Zone, contains a Burgess Shale-type Lagerstätte with many well-preserved fossils known collectively as the Kaili Biota. In terms of age, this biota is located between the two most important and famous Cambrian Lagerstätten: the middle Lower Cambrian Maotianshan Shale (containing the Chengjiang Biota), also from China: and the Middle Cambrian Burgess Shale, known from Canada.
Some other notable fossils discovered at Kaili are putative invertebrate eggs and embryos, trace fossils of the genus Gordia (not to be confused with the Gordian worms), as well as Naraoia, chancellorids, Microdictyon, Wiwaxia, and Marrella. Furthermore, the possible moss Parafunaria is also known, marking the earliest likely fossil of land plants. However this fossil has been disputed, as its Cambrian age means more conclusive proof is needed to determine whether it truly is a moss.
The Kaili Formation is subdivided into three trilobite zones: Bathynotus holopygous–Ovatoryctocara granulata Zone Oryctocephalus indicus Zone Olenoides jialaoensis Zone
Paleobiota Animals
AnimalsGenusSpeciesHigher taxonNotesImagesSkania?"S." sundbergiAcercostracaLikely does not belong to the genusOlenoidesO. paraptusDorypygidaePreserved with gut contentsAlicarisA. kailiensisArthropodaPseudoarctolepisP. semicircularisHymenocarinaDiffers from the type species in having smaller semicircular "wings"TuzoiaT. bispinosaTuzoiidaePreserves ontogenyForfexicarisF. reticulataMegacheira?Relatively similar to the type speciesLeanchoiliaL. spMegacheiraPreserves neuroanatomyFuxianhuiida indet?UnapplicableDeuteropodaKnown from a poorly preserved specimen with trilobite fragments inside its gutMollisoniaM. sinicaMollisoniidaDiffers from Burgess Shale specimens in the shape of the tail and head shieldsUrsulinacarisU. cf. grallaeHurdiidaeOne of the first hurdiids from Miaolingian ChinaOttoiaO. guizhouensisArchaeopriapulidaMay not actually belong to Ottoia?HaplophrentisH. carinatusHyolithidaOne specimen found with several eocrinoids growing on its shell in lifeNisusiaN. guizhouensis, N. granosaKutorginidaOne of the few rhynchonelliforms known from the CambrianKailidiscusK. chinensisEdrioasteroideaStrongly resembles other echinoderm clades in several featuresGlobeocrinusG. globulusEocrinoideaShort-stalked, over three times as abundant as SinoeocrinusSinoeocrinusS. luiEocrinoideaSynonymous with a wide range of other proposed eocrinoids, has a complex ontogenyTurbanicystisT. inflataEocrinoideaHas a very short but broad stalk, which likely secreted a "glue" to cement it to substratePararotadiscusP. guizhouensisEldoniidaeSmall brachiopods and echinoderms likely grew on some specimens in lifeDinomischusD. isolatus?Dinomischidae (stem-Ctenophora)Only known from one specimenAngulosuspongiaA. sinensisVauxiidae (Demospongiae)First non-Laurentian vauxiid, bears silliceous spiculesAllonniaA. phrixothrix, A. erjiensisChancelloriidaeLatter species has especially dense scleritesArchiasterellaA. anchoriformisChancelloriidaeOne of the two species in the genus known from complete fossilsChancelloriaC. zhaoi, C. erosChancelloriidaeOne specimen of the latter species has a smaller C. eros growing on top of it
Other taxa
Other taxaGenusSpeciesHigher taxonNotesImagesParafunariaP. sinensisBryophyta?Possibly the earliest embryophyte fossil, but this has been doubted due to insufficient evidenceParallelphytonP. tipicaViridiplantae?Bears differentiation similar to "proto-plants" and the extant FritschiellaWalcottophycusW. gygesBryopsidales?Formerly placed within Bosworthia
GSSP for the Cambrian Series 3 An outcrop of the Kaili Formation, the Wuliu-Zengjiayan section, was a candidate for the GSSP for the beginning of the 5th stage of the Cambrian. The FAD of two trilobites from the formation are proposed to be the official stage boundary, Oryctocephalus indicus and Ovatoryctocara granulata. Both can be correlated with formations of similar age in Siberia and China. In 2018, GSSP for the Miaolingian series (Cambrian Series 3, "Middle" Cambrian) as well as the Wuliuan stage was finally defined in this formation.
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