Kaili Formation

Kaili Formation
Stratigraphic range: Cambrian 513–506 Ma PreꞒ Ꞓ O S D C P T J K Pg N
Type	Geological formation
Thickness	~200 m (660 ft)
Lithology
Primary	Claystone, mudstone, shale
Other	Siltstone, marl, limestone
Location
Coordinates	24°54′N 102°30′E / 24.9°N 102.5°E / 24.9; 102.5
Approximate paleocoordinates	35°06′N 161°18′E / 35.1°N 161.3°E / 35.1; 161.3
Region	Guizhou
Country	China
Type section
Named for	Kaili
Kaili Formation (China) Show map of China Kaili Formation (Guizhou) Show map of Guizhou

The Kaili Formation (simplified Chinese: 凯里组; traditional Chinese: 凱里組; pinyin: Kǎilǐ zǔ) is a stratigraphic formation which was deposited during the Lower and Middle Cambrian (~513 to 506 million years ago). The formation is approximately 200 metres (660 ft) 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

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon

Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.

Animals
Genus	Species	Higher taxon	Notes	Images
Skania?	"S." sundbergi	Acercostraca	Likely does not belong to the genus
Olenoides	O. paraptus	Dorypygidae	Preserved with gut contents
Alicaris	A. kailiensis	Arthropoda
Pseudoarctolepis	P. semicircularis	Hymenocarina	Differs from the type species in having smaller semicircular "wings"
Tuzoia	T. bispinosa	Tuzoiidae	Preserves ontogeny
Forfexicaris	F. reticulata	Megacheira?	Relatively similar to the type species
Leanchoilia	L. sp	Megacheira	Preserves neuroanatomy
Fuxianhuiida indet?	Unapplicable	Deuteropoda	Known from a poorly preserved specimen with trilobite fragments inside its gut
Mollisonia	M. sinica	Mollisoniida	Differs from Burgess Shale specimens in the shape of the tail and head shields
Ursulinacaris	U. cf. grallae	Hurdiidae	One of the first hurdiids from Miaolingian China
Ottoia	O. guizhouensis	Archaeopriapulida	May not actually belong to Ottoia?
Haplophrentis	H. carinatus	Hyolithida	One specimen found with several eocrinoids growing on its shell in life
Nisusia	N. guizhouensis, N. granosa	Kutorginida	One of the few rhynchonelliforms known from the Cambrian
Kailidiscus	K. chinensis	Edrioasteroidea	Strongly resembles other echinoderm clades in several features
Globeocrinus	G. globulus	Eocrinoidea	Short-stalked, over three times as abundant as Sinoeocrinus
Sinoeocrinus	S. lui	Eocrinoidea	Synonymous with a wide range of other proposed eocrinoids, has a complex ontogeny
Turbanicystis	T. inflata	Eocrinoidea	Has a very short but broad stalk, which likely secreted a "glue" to cement it to substrate
Pararotadiscus	P. guizhouensis	Eldoniidae	Small brachiopods and echinoderms likely grew on some specimens in life
Dinomischus	D. isolatus?	Dinomischidae (stem-Ctenophora)	Only known from one specimen
Angulosuspongia	A. sinensis	Vauxiidae (Demospongiae)	First non-Laurentian vauxiid, bears silliceous spicules
Allonnia	A. phrixothrix, A. erjiensis	Chancelloriidae	Latter species has especially dense sclerites
Archiasterella	A. anchoriformis	Chancelloriidae	One of the two species in the genus known from complete fossils
Chancelloria	C. zhaoi, C. eros	Chancelloriidae	One specimen of the latter species has a smaller C. eros growing on top of it

Other taxa

Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon

Notes
Uncertain or tentative taxa are in small text
crossed out taxa are discredited.

Other taxa
Genus	Species	Higher taxon	Notes	Images
Parafunaria	P. sinensis	Bryophyta?	Possibly the earliest embryophyte fossil, but this has been doubted due to insufficient evidence
Parallelphyton	P. tipica	Viridiplantae?	Bears differentiation similar to "proto-plants" and the extant Fritschiella
Walcottophycus	W. gyges	Bryopsidales?	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.