THE GREATEST HITS OF ALL TIME: THE RISE AND FALL OF COMMON GENERA IN THE FOSSIL RECORD

There is a strong interest in success, in particular when it can be quantified as high relative ranking. This includes “top ten” song hits, championship sports teams, university status, and citation metrics. In some of these cases, success is ephemeral, whereas in others, high ranking persists for extended periods of time. In evolution, one possible measure of success is ubiquity, that is, how widespread and common is the taxon. Certain fossil taxa are so ubiquitous that they are characteristic of their time periods; examples include Inoceramus and Phacops. Even these ubiquitous taxa, although they may be extinction resistant, are not extinction proof. We have used the Paleobiology Database to determine whether there are shared patterns in the histories of the “greatest hits” genera in the fossil record; i.e., those genera that are the most common representatives of their higher taxon, as measured by number of occurrences, in at least one of the ca. 10 million year bins used in the PaleoDB. Raw occurrence data was converted to relative rank for each bin. Groups examined include brachiopods, gastropods, cephalopods, bivalves, crinoids, and echinoids. We determined the patterns of rise and fall of the top taxa to the number one position, the number of bins that a genus persisted at or near the top, and the number of top 10, 20, 50 and top 25% of genera in one bin that persisted until the next. We also examined the number of species per common genus. We found no consistent trajectory for number one genera; most rose and disappeared from the top position within one or two bins, others persisted at or near the top for extended periods. For example, Turritella has been the most common gastropod since the Cretaceous. In contrast, the brachiopod Neospirifer was at the top position for only a single bin. Not surprisingly, turnover in the top ranks is associated with intervals of mass extinction. Commonly occurring genera also tend to be species rich.