The ratios of the taxa of different ranks in the fossil record and the reconstruction of the species diversity of the Phanerozoic marine biota

The ratios of coexisting marine phyla (p), classes (c), orders (o), families (f), and genera (g) through the Phanerozoic can be described as an exponential trend. The number of genera can be calculated as an interval between f.(k-sigma) and f.(k+sigma), where k is the arithmetic mean of f/o, o/c, and c/p; and sigma is their standard deviation. A reconstruction of species diversity by the same method shows a good fit with other independent estimates. A possibility of quantitative approximation of completeness of the fossil record based on the ratios of taxa of different rank is demonstrated.