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These shales appear very early in the Cambrian sequence in China. They were discovered around 1984 and have been 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. 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 fishesAtlantic herring, Clupea harengus one of the most abundant species in the world Photo A fish is a poikilothermic (cold-blooded) water-dwelling vertebrate with gills. There are over 27,000 species of fish, making them the most diverse group of vertebrates.. See HaikouellaThe Haikouella is a probable chordate from the Lower Cambrian beds of Xiangchiang, Yunnan, China. It is similar to the form Yunnanozoon which is almost somewhat more primitive and is possibly a hemichordate. There are anatomical differences from Yunnanozo, HaikouichthysThe Haikouichthys is a primitive fishlike animal from the Lower Cambrian Maotianshan shales of China. Cladistic analysis indicates that the animal is probably a primitive agnathid fish most closely related to the Lampreys. It is about 2. 5cm long and is n, Yunnanozooan, MyllokunmingiaThe Myllokummingia is a primitive probably agnathid (jawless) fish from the Lower Cambrian Maotianshan shales of China thought to be a chordate. It somewhat resembles modern hagfish. It is described as 28mm long and 6mm high. The holotype was found in the. More mundane forms such as trilobiteAgnostida Redlichiida Corynexochida Lichida Nektaspida? Phacopida Proetida Asaphida Harpetida Ptychopariida Trilobites are extinct arthropods in the class Trilobita . They appeared in the Cambrian era and flourished throughout the lower Palaeozoic befores, 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.