Comparison of divergence times from fossils with those estimated from molecular data and four calibration points for the sea urchin data.

For k-medoids (k-med), the optimal number of local clock is at k* = 3; the minimum sum of squared distance (SSD) is at k = 12.
Notes–From Smith et al. (2006): Fig. 5 (¶) and Table 2 (†). ¥ Naïve approaches, for which knowledge of the actual fossil dates is not taken into account to estimate divergence dates. ‡ Calibration points (set as minimum ages for PL); root age is fixed. na: not applicable. PL(CV) contains age estimates obtained by penalized likelihood with cross-validation; with PL(SSD), the penalty is selected by minimizing SSD.