Time-dependent birth–death model fitted to a nearly complete extant timetree of the Cetacea, under the assumption of extinction rates of zero (μ = 0), compared to a congruent model in which the extinction rate is close to the speciation rate (μ = 0.9λ). a, LTT of the tree, compared to the dLTT predicted by the two models. b, Speciation rates (λ) and extinction rates (μ) of the two models. c, Net diversification rates (r = λ − μ) of the two models. Further details are provided in Supplementary Information section S.4.