Lyellian percentages for the Arctic and Antarctic faunas of the Pliocene and Paleocene/Eocene intervals.

Data from the Paleocene/Eocene interval are limited to the genus level and come from datasets collected for this manuscript (see SI Table 1 for references). Arctic Pliocene percentages from Valentine et al. 2008 [52]. Antarctic Pliocene percentages were obtained from references listed in Beu 2009 [15]. Confidence intervals were calculated using binomial probabilities on percentage data as presented in Raup 1991 [53].