The average extinction rates of index species per m. y. are computed by means of a count-of-biozones metric (Trammer 2014). These rates and the average extinction rates of genera belonging to biostratigraphically important groups, calculated according to three different methods, show congruent rises and falls from the Cambrian to the Neogene. The extinction rates of genera are, thus, a relatively good predictor of species extinction rates.
The count of biozones as an approximate measure of the origination and extinction rates of index taxa (mostly species) is proposed. The mean number of extinctions of these taxa per m.y. is 1.136 (Palaeozoic mean 0.902, Mesozoic mean 1.680, Cenozoic mean 0.789). In contrast with the majority of taxa, the originations and extinctions of index taxa, as well as of other taxa belonging to biostratigraphically important systematic groups, seems to be continuous.
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Estimates derived from the literature suggest that dinosaurs, even if they had a mammalian-type metabolism, produced globally much more biomass than mammals for the same amount of energy consumed. The average body mass of an individual dinosaur was several thousand times greater than in the case of mammals. Dinosaurs were one to several hundred times less numerous than mammals and, in comparison to mammals, the average number of individuals per dinosaur species was several to a dozen or so times lower than in mammals.
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