Fossil Paradise

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4 March 2009 No Comment

Fossils are the remains of of animals, plants, and other organisms which existed long ago, giving us valuable clues to various life forms existed once on planet. Paleontology is the study of fossils across geological time, dealing with how they were formed and also their evolutionary relationships between taxa . A preserved specimen is called a “fossil” if it is older than some minimum age, most often the arbitrary date of 10,000 years ago. Its not that all former life will be preserved as fossils , in fact very few escape from vanishing without any trace. Fossilization depends on many aspects including nature of body form ( usually hard parts such as shells ,bones etc survive fossilization and soft bodies organisms are difficult to be found as fossils) and also environmental conditions in which the organism lives also matter a lot .
Fossil sites with exceptional preservation — sometimes including preserved soft tissues — are known as Lagerstätten or A Lagerstätte is a sedimentary deposit that exhibits extraordinary fossil richness or completeness. Today we are going to talk briefly about two of them:

Fossils of Chengjiang:
Its a very well accepted fact now that during early Cambrian period (544 million to 520 million years ago) there was an evolutionary radiation of most major groups of complex animals. This sudden appearance of various animal life forms is termed as Cambrian explosion and this was possible by studying the fossil record found from various parts of the world.These early fossils represent the roots for the tree of all modern animal life.

The Chengjiang biota is one of the most remarkable fossil discoveries ever made. Among the hills and lakes of Yunnan Province, South China, deposits of ancient mudstone, 525 million years old, have yielded a spectacular variety of exquisitely preserved fossils that record the early diversification of animal life. Ever since the first specimen discovery in 1984, it has become home to thousands of exceptionally preserved soft-bodied fossils and the list is still growing .Chengjiang lagerstatte has a unique distinction of providing insights into issues many in dispute, for understanding of the paleobiology of multicellular animals in general, and chordates in particular. This fossil paradise along with Burgess Shale Fauna of Field, British Columbia provide a lens to view the appearance on earth of all the major phyla in existence today.
The Cambrian Fossils of Chengjiang, China: The Flowering of Early Animal Life written By: Hou, Xian-guang; Aldridge, Richard John; Bergstrom, Jan is an excellent book providing fossil enthusiasts with an overview of the fauna found in China’s great fossil treasure.

Burgess Shale
The Burgess Shale is a very famous fossil Lagerstätte named after the nearby Burgess Pass and and is famous for the exceptional preservation of the fossils found within it, in which the soft parts are preserved.The Burgess Shale was discovered by Charles Walcott in 1909, towards the end of the season’s fieldwork. Scientists believe the deposits were formed when areas of muddy ocean floor slid into a lower place creating an anoxic (less of oxygen) environment that was particularly favorable to fossilization because decay was inhibited.It is 505 million years (Middle Cambrian) in age, making it one of the earliest fossil beds to preserve the soft parts of animals.
It was Stephen jay gould who brought to light one of the most spectacular paleontological discoveries of all time through his book “Wonderful Life: The Burgess Shale and the Nature of History” , published in 1989. He was of the opinion that the extraordinary diversity of the fossils found at shale indicates that life forms at that time were much more diverse than those that we see today, and that many of the unique lineages were evolutionary experiments that became extinct.