The pyloric pattern of the lobster (Panulirus interruptus) stomatogastric ganglion comprises two phase-maintaining subsets.

The pyloric pattern approximately maintains phase over a three- to fivefold frequency range when the pattern is defined by the pacemaker burst beginning. However, in this reference frame certain pattern elements maintain phase better than others, which suggests phase-maintaining subgroups might exist. Reanalysis of these data in reference frames defined by each element shows the pattern contains two groups of pattern elements within which phase is well maintained but between which maintenance is relatively poor. A third element shows intermediate maintenance with each group. If ventricular dilator neuron burst beginning (VDB) is chosen as pattern beginning, all members of one group occur early in the pattern, all members of the other occur late in the pattern, and the intermediate element occurs between the groups. Thus, at least for phase maintenance, VDB is a "natural" pyloric pattern beginning. These results suggest full description of complex patterns is best achieved by analysis in many reference frames.