Ediacara animals
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Ediacara Hills --- South Australia a rich deposit of Precambrian fossils. The first finds at this site were made in 1947 by the Australian geologist R.C Spring.
* All the Ediacara animals were soft bodied; none had hard shells, and their soft tissues were strengthened by nothing more than spicules: needdless of calcium carbonate that served as a primitive support. All,
of course, lived in the sea, some fixed to the bottom, some crawling and others free-floating or swimming. The soft-bodied nature of these fossils justifies the characterization of Pre-cambrian as the "age of the jellyfish".
* The development of shell in the Cambrian was not a result of a sudden change in the habits or habitats of the animals. Rather, shells appeared as a step forward in biochemical evolution. Calcium metabolism underwent a change that produced hard shells and other skeletal material, providing the protection and mechanical support so important to the more advanced animals.
* The interesting suggestion has been made that shells evolved as a protective measure against harmful radiation: the ultra-violet radiation rather than against living predators. The reasoning is that the ultra-violet radiation of the sun would have been much stronger without the ozone layer, which may not have formed until an excess of oxygen had been built up by plants.
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