Cyp subtropicum does seem to have 'primitive' characters for the plicate-leaved genera, though the overt flower similarity to Selenipedium (incl the column) could be pollinator syndrome convergence. 'Primitive' Paphs, Phrags, and Mex all have the basically inflated labella that almost all Cyps and all Selens bear. Thus, the inflated pouch feature can be considered 'primitive' in the whole slipper orchid group, by the principle of parsimony. The main features that stick out for me with Cyp subtropicum are the stem habit, incl height and leaf form, and many-flowered raceme. This gives one an impression of relatedness to Cyp californicum. The habit is also similar to Cyp irapeanum, and based on molecular data, irapeanum is the baslmaost Cyp, probably followed by californicum, then the rest. So, it would not surprise me if subtropicum were also very near the evolutionary base of the Cyps. East Asia/North America disjunctions are very well-known in other plant groups, and both californicum and irapeanum are good contenders for this connection (which probably dates to a Bering land bridge connection).
Best,
Vic
