The following key is partially adapted from R. Singer & L. D. Gómez (Brenesia 22: 163-181. 1984).	Interactive Key
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Vouchers for all collections are on deposit in the mycological herbaria at Universidad de Costa Rica (USJ) or Instituto Nacional de Biodiversidad (INB). Duplicates are in the Field Museum (F) and the New York Botanical Garden (NY).

1. Spores amyloid . . . . P. guanacastensis Gómez (questionable taxon)

1. Spores inamyloid or dextrinoid . . . . 2

2. Clamp connections present at hyphal septa; NH₄OH not bluing pileus surface . . . . P. fibulatus Singer, et al. [currently only known from oak forests of Colombia, but might be expected in Costa Rica]

2. Clamp connections absent or only very exceptional; NH₄OH typically reacting bluish green on pileus surface (if negative then basidiomata bright orange and spores ovoid). . . . 3

3. Associated with alder (Alnus acuminata) . . . . P. caballeroi Singer

3. Associated with oak (Quercus spp.) . . . . 4

4. Basidiomata orange-red; spores ovoid . . . . P. aurantiacus Halling & Mueller

4. Basidiomata colored otherwise; spores fusoid to subcylindric . . . . 5

5. Basal mycelium white when fresh and when dried; pileipellis lacking chains of sphaerocyst-like isodiametric elements . . . . 6

6. Hymenial cystidia thinwalled and lacking incrustions . . . . 7

7. Lamellae frequently cyanescent . . . . 8

8. Pileus tan to brown . . . . P. bellus (Massee) Corner

8. Pileus pinkish purple . . . . P. purpurellus Singer [currently only known from oak forests of Colombia, but might be expected in Costa Rica]

7. Lamellae not cyanescent . . . . P. alborufus sp. nov.

6. Many cystidia thickwalled and incrusted; lamellae rarely cyanescent . . . . P. centroamericanus Singer & Gómez

5. Basal mycelium yellow when fresh and when dried; pileipellis with chains of isodiametric elements . . . . P. phaeoxanthus Singer & Gómez

9. Cystidia not incrusted . . . . var. simplex

9. Cystidia distinctly incrusted with a resinous material . . . . var. phaeoxanthus