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I found a paper estimating the number of species currently living on earth. Now I'm wondering If anybody tried to estimate the number of species that have lived on earth. I'm familiar with problems of "species concepts". But I'm sure, there is at least a number of all known fossils.
EDIT: In contrast to the question How many organisms have ever lived on Earth? I'm asking for species and not for individuals. The answer to my question can be used to ansewer the queston for the number of organisms. But still, The questions is different.