Estimated age of the root in the presence of an abrupt acceleration then deceleration of ancestral rates

These estimates are from a worked example with an abrupt acceleration then deceleration (the red line of Figure 4A) which occurs deeper in the tree than the calibration points. The true root age is 80.0 mya. The estimated values are made by minimizing the cost functions (that also appear in table 1), but upon the weighted constrained tree of figure 4A.