Add Yahoo as a preferred source to see more of our stories on Google. Ancient animal history is extremely difficult to reconstruct, for a number of reasons. Some of the earliest creatures in existence ...
ZME Science on MSN
New fossils, including one that looks like the sandworm from Dune, rewrite the dawn of animal life
If you trace the animal family tree back through the fossil record, the trail usually goes cold about 539 million years ago.
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