The Cambrian fossils of Chengjiang, China: The flowering of early animal life 

Among the hills and lakes of the Chengjiang area, Yunnan Province, South China, 525 million year old mudstones are yielding a spectacular variety of exquisitely preserved fossils. Since the discovery of the first specimens in 1984, many thousands of fossils have been collected, exceptionally preserving not just the shells and carapaces of the animals, but also their soft tissues in fine detail. This special preservation has produced fossils of rare beauty, and they are also of outstanding scientific importance.

The aim of this book is to introduce professional and amateur palaeontologists, and all those fascinated by evolutionary biology, to the aesthetic and scientific quality of the Chengjiang fossils.

Images from the book

	Maotianshan in the Chengjiang area, Yunnan Province, the site of the first find of soft-bodied fossils
	Collecting from the Lower Cambrian pale coloured mudstones at Maotianshan in the Chengjiang area, Yunnan Province
	The geological record with some key events in the history of life
	Cricocosmia jinningensis , a nematomorph worm, x7.8. This species is known from thousands of specimens. The anterior proboscis, armed with spines, and the dark-coloured gut, are often clearly seen. It is known only from the Lower Cambrian of Yunnan Province
	Paraselkirkia jinningensis , a priapulid worm, x13.8. Hundreds of specimens are known for this species. The narrow, elongate, tapering tube presumably housed the trunk of the animal, and anteriorly there is a spinose proboscis for use in feeding and burrowing activities. This species has been recorded only from the Lower Cambrian of the Chengjiang area.
	Fuxianhuia protensa , an arthropod, x2.1. It has a wide ‘head shield' and broad, anterior part to its trunk, which are succeeded by a narrower abdomen. This animal lived on the sea bottom, and the pair of grasping appendages in the head indicates that it may have been carnivorous. The species is known only from the Chengjiang biota.
	Microdictyon sinicum , a lobopodian, x7.2. It is uncertain which is the head end in this species, which has a trunk on which there are perforated plates, and annulated appendages with distal claws that it probably used for attachment. Microdictyon is known from various localities of Cambrian age globally, though this species has only been found in the Chengjiang area.
	Yunnanozoon lividum , an enigmatic form, x6.0. This worm-like animal may have been a deposit feeder. It has only been recorded from the Chengjiang biota.
	Myllokunmingia fengjiaoa , a chordate, x5.8. Myllokunmingia is one of the most celebrated fossils from the Chengjiang biota, as it is the earliest known vertebrate. It could certainly swim, though its mode of feeding is as yet unknown. It has been found only in the Lower Cambrian of the Haikou area, Yunnan Province.
	Anomalocaris saron , reconstruction. Anomalocaris , a large animal with large anterior appendages, was a carnivorous predator. It is one of four anomalocaridid genera in the Lower Cambrian of the Chengjiang area; each contains a single species, all of which are known only from this biota. The affinity of the anomalocaridids has been much debated, their morphology inviting comparison with several phyla, including various worm groups, kinorhynchs, lobopodians and arthropods.

Significance of the material
Fossil deposits such as that from Chengjiang that preserve soft-part anatomy, that is Konservat-Lagerstätten, are very rare and crucial to our knowledge of the history of life on earth. They provide a far more complete record of the palaeobiology and true nature of past communities than does the normal shelly fossil record, and so they represent unique windows on ancient life. The Cambrian Period (490-540 million years ago) witnessed the first appearance in the fossil record of nearly all the major animal groups that have sustained global biodiversity to the present day, these appearances comprising the so-called Cambrian Explosion. The Chengjiang fossils are testimony of this event and study of them is contributing fundamentally to our understanding of the early evolution of animal life.

Geological setting
The sediments containing the biota were deposited during Early Cambrian times in a shallow marine setting on the Yangtze Platform area, which during this period formed part of the South China (tectonic) Plate situated near the equator.

Preservation of specimens
The animals are mostly preserved as flattened impressions; some have low relief. Their superlative preservation is frequently enhanced by the colour contrast between the fossils and the background sediment. The detailed nature and the genesis of their preservation are currently under investigation. Many specimens must have fossilised remarkably quickly, with only limited or no post-mortem transport, as their delicate tissues have survived without signs of decay or disassociation.

Composition of the biota
There is a diverse range of organisms, including sponges, cnidarians, ctenophores, nematomorph and priapulid worms, hyolithids, lobopodians, arthropods, anomalocarids, brachiopods, and chordates, together with many enigmatic forms. The total number of species is more than 100, with arthropods comprising over 60% of all specimens recovered.

Ecology
The ecology of many species, and that of the community as a whole, has at present been only partially determined. However it is already clear that even in these ancient, Early Cambrian seas, this was a fairly sophisticated ecosystem with a wide variety of feeding types, including filter feeders, scavengers, predators and, arguably, deposit feeders. Most species lived within, on, or close to the sea bottom; some were sessile, while others crawled on the seabed or were swimmers in the water column.