FIG. 3: Analytical influence of soft maximum prior selection on the avian evolutionary timescale (modified from Berv and Field, 2018). Colored boxes represent the major crown bird subclades and correspond to the color scheme from figure 1. Underlying black phylogeny represents the preferred time tree from Prum et al. (2015), applying a soft maximum age of 86.5 Ma for the crown bird MRCA. Red arrows illustrate shifts in estimated clade ages induced by removing this soft maximum prior, with other analytical parameters kept the same. The most severe branch length extensions occur on the deepest lineages of the tree (the lineages most likely to have crossed the K-Pg boundary). However, an important caveat is that the Paleogene calibrations in this analysis have soft maxima informed directly by the K-Pg boundary itself. K-Pg boundary denoted by red line and asteroid; age of the fossil avialan-rich Niobrara Formation "Niobrara Prior" indicated by blue dashed line. Ichthyornis reconstruction modified from Marsh (1880).