Figure 1.

The 28 candidate clock partitions (25 morphological, three molecular) and their optimal grouping patterns when assigned multiple clocks from n = 1, 2, 3, 4, …, 13 clocks or pacemakers (optimal number = 8). Note that the three molecular partitions consistently form a single clock, separate from all morphological partitions. Some groups of morphological partitions also consistently fall within the same clock (e.g. upper teeth; forelimb and hindlimb skeleton; skin, urinogenital and reproductive systems; soft anatomy of head and alimentary systems). (Online version in colour.)