Fig. 8

Alternative log-normally distributed priors used to account for temporal uncertainty of calibration nodes. Each prior probability density function (PDF) is characterized by a hard minimum bound of 18 Ma (set by the age of the calibration fossil), a standard deviation (σ) of 0.5, and a variable mean (μ) (in real space) that probabilistically models the extent to which the node age spreads into the past: μ = 19 (black), μ = 24 (blue), and μ = 29 (red). The lower limit of the x-axis interval defining the area shaded under each curve corresponds to its 95th percentile soft maximum bound (P₉₅ SMB): 20 Ma (black), 30 Ma (blue), and 40 Ma (red)