Extinctions and originations
In the minds of most people prehistoric extinctions are associated with the demise of the dinosaurs, which is why we chose this picture of dinosaur fossils being removed from rock strata. But evidence of extinctions of species and the rise of new species occurs throughout the fossil record from 540 million years ago when hard-shelled animals first appeared. The paper by James Kirchner and Anne Weil referenced in our book gives details of the compilation of their data on marine fossil records which they analysed, and kindly supplied to us. The four data files we make available here each have two columns, the first being the date in Myr before present associated with the series value, and the second being the logarithm of the series value. The file LGEPS.txt is of the log percentage of extinctions of genera and the file LGOPS.txt is of the log percentage of originations. The corresponding files for the log percentage of extinctions of families are LFEPS.txt and LFOPS.txt. There are 108 values of the genera series and 106 values of the families series.