Paper detail

A ubiquitous ~62 Myr periodic fluctuation superimposed on general trends in fossil biodiversity: II, Evolutionary dynamics associated with periodic fluctuation in marine diversity

We investigate evolutionary dynamics related to periodicity fossil biodiversity. Coherent periodic fluctuation in origination/extinction of marine genera that survive <45 million years is the source of an observed ~62 million year periodicity analyzed in Paper I. We also show that the evolutionary dynamics of "long-lived" genera (those that survive >45 million years) do not participate in the periodic fluctuation in diversity and differ from those of "short-lived" genera. The difference between the evolutionary dynamics of these 2 genera classes indicates that the periodic pattern is not an artifact of variation in quality of the geologic record. The interplay of these two previously undifferentiated systems, together with the secular increase in abundance of "long-lived" genera, is probably the source of heretofore unexplained differences in evolutionary dynamics between the Paleozoic and post-Paleozoic as reported by others. Testing for cycles similar to the 62 Myr cycle in fossil biodiversity superimposed on the long-term trends of the Phanerozoic as described in Paper I, we find a significant (but weaker) signal in sedimentary rock packages, particularly carbonates, which suggests a connection. The presence of a periodic pattern in evolutionary dynamics of the vulnerable "short-lived" component of marine fauna demonstrates that a long-term periodic fluctuation in environmental conditions capable of affecting evolution in the marine realm characterizes our planet. Coincidence in timing is more consistent with a common cause than sampling bias. A previously identified set of mass extinctions preferentially occur during the declining phase of the 62 Myr periodicity, supporting the idea that the periodicity relates to variation in biotically important stresses. Further work should focus on finding links to physical phenomena that might reveal the causal system or systems.