Fig. 2: Time-scaling of ARR rates.

ARR estimates of net diversification rate decrease sharply through time as a function of the timescale over which they are computed. For each timepoint, rates were computed using an estimate of stem clade age and the standing diversity at the focal time, as in Fig. 1a–c Rates were computed using relative extinction rates of 0.5 (red circles) and 0.9 (blue triangles), which are widely used in neontological studies. Gray polygons show the underlying diversity trend for each clade on a proportional scale (see Supplementary Fig. 2 for actual values). The decay in rates occurs regardless of the form of the underlying diversity trend. Clades that increased in diversity through time (e.g., Bivalvia, Gastropoda, Dinosauria) show the same general pattern as extinct or declining clades. This temporal decay in rates is the expected pattern under null models where species richness fluctuates randomly in time with no underlying biological process (Supplementary Fig. 3).