The Cambrian explosion is the name given to the discovery of a vast range of fossils of organisms that existed about 500 million years ago. The first discovery of them was made in the Burgess Shale region of Canada in 1909 and other troves were later found in China and Australia. But now comes a report of an extremely rich new trove that has been discovered, again in China.

Paleontologists found thousands of fossils in rocks on the bank of the Danshui river in Hubei province in southern China, where primitive forms of jellyfish, sponges, algae, anemones, worms and arthropods with thin whip-like feelers were entombed in an ancient underwater mudslide.

The creatures are so well preserved in the fossils that the soft tissues of their bodies, including the muscles, guts, eyes, gills, mouths and other openings are all still visible. The 4,351 separate fossils excavated so far represent 101 species, 53 of them new.
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The fossilised organisms date back to 518m years ago when life on Earth experienced a massive burst in diversity known as the Cambrian explosion. The event, at the dawn of animal life, marked the arrival of all manner of unusual creatures. Many went extinct as evolutionary dead-ends, but others went on to form the first sturdy branches of the tree of life.
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“These fossils help us to piece together the steps that evolution took as animals evolved from whatever squishy blob represents their common ancestor to the rich diversity of lineages alive today,” he added. “Because some of the preserved organisms are much simpler than their living relatives, they help us to tease apart how complex organs such as brains could be assembled through blind evolutionary processes.”

The paper reporting these findings in the journal Science can be read here and an accompanying article explaining the significance of the findings can be read here. Both are behind paywalls.

Evolution deniers ask “Where is the missing link?” Everything that has been found that dates between the Cambrian fossils and current species are of course ‘missing links’. But don’t expect deniers to accept that. They will keep asking that question because they have nothing else. As Herbert Spencer wrote back in 1852, “Those who cavalierly reject the Theory of Evolution as not being adequately supported by facts, seem to forget that their own theory is supported by no facts at all. Like the majority of men who are born to a given belief, they demand the most rigorous proof of any adverse belief, but assume their own needs none.”