Maotianshan shales

The Maotianshan shale is a lower Cambrian (Atdabanian) rock formation, of ca 522 Mya, now lying exposed in the Yunnan Province of China in the villages of Ercaicun and Chengjiang near the city of Kunming. The Maotianshan shales are part of the Qiongzhusi Section of the Yu'anshan Member of the Heilinpu Formation and comprises a large exposure some 50 meters thick of mudstone sedimentary strata. The Chengjiang biota is extremely diverse, including many excellently-preserved soft-bodied fossilized organisms that form a major Lagerstätte, "probably the most significant exceptional preservation above the Precambrian-Cambrian boundary (c. 543 Ma)" ^*. At the time these sediments were laid down, this section of the Yangtze plateau lay in an equatorial zone. Some brachiopods that are found in situ and the gut contents of some mud-ingesting animals both indicate a warm, shallow sea with a muddy bottom.

These shales were discovered around 1984 by Xianguang Hou, and its fossils have been and continue to be extensively studied by both Chinese and Western paleontologists. The shales contain a very broad and well-preserved fauna including many of the taxa found in the better known, and substantially younger, Burgess Shale of British Columbia, as well as the somewhat younger Emu Bay shale of South Australia. The fauna is often referred to as "the Chengjiang biota".

In addition to Anomalocaris, Opabinia, Hallucigenia, and other spectacular forms familiar from the Burgess shales, the Maotianshan shales include at least four possible types of chordates, two of which appear to be true fishes. See Haikouella, Haikouichthys, Yunnanozoon, Myllokunmingia. A diversity of more familiar forms such as trilobites, brachiopods, and sponges are also present.

The Maotianshan shales provide even stronger evidence than does the Burgess shale for a Cambrian Explosion wherein a large number of very different animal body plans seem to have appeared in a disconcertingly short time interval.

Partial List of Genera from the Maotianshan Shales (Chengjiang Biota)

Arthropods

Acanthomeridion
Anomalocaris
Canadaspis
Chengjiangocaris
Chuandianella
Cindarella
Eoredlichia, a trilobite
Fortiforceps
Fuxianhuia
Isoxys
Jianfengia
Kuamaia
Kuanyangia, a trilobite
Leanchoilia
Misszhouia
Naraoia
Primicaris
Retifacies
Saperion
Sinoburius
Skioldia
Squamacula
Xandarella
Yunnanocephalus, a trilobite

Worms and relatives

Hallucigenia
Microdictyon
Palaeoscolex

Chordates

Vetulicolia

Others

Dinomischus
Eldonia
Maotianshania
Opabinia
Xianguangia
Cotyledion

References

- A catalogue of sites of exceptional fossil preservation produced by MSc palaeobiology students at University of Bristol's Department of Earth Sciences.

Cambrian | Paleontology | Yunnan | Geologic formations

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