Fig. 2: The evolution of genus size and R_calc/R_fix.

a–e, Stack plots represent coccolith counts for the 15–20 μm (a), 10–15 μm (b), 8–10 μm (c), 5–8 μm (d) and 3–5 μm (e) size fractions. Each stack plot represents a normalized closed sum of the four genera. Also shown to the right of each plot is the distribution of associated R_calc/R_fix values (for full species percentage abundance counts, see Extended Data). Reconstructed R_calc/R_fix values are shown for each of the four dominant genera across all sediment size fractions. R_calc/R_fix is not presented for Chiasmolithus in d or e and Reticulofenestra is not show in a due to a lack of coccolith contribution to the respective size fractions resulting in an underconstrained value. Presented R_calc/R_fix represent the values that minimize the error between measured and modelled CIVE_mean. Error bars represent 95% of Monte Carlo realizations. The solid black line associated with each stack plot represents the abundance-weighted average of each size fraction R_calc/R_fix. Dashed lines bound 95% of calculated weighted R_calc/R_fix values. The weighted R_calc/R_fix values are on an equivalent scale to the subplots on the right-hand side. Also shown in a–e are key periods during the Eocene, including the ETM2, EECO and MECO.