1. Stipules entire; erect branched shrubs.....Amphidasya venezuelensis
1'. Stipules laciniate; herbs, low sparsely branched shrubs, or unbranched shrubs.
2. Calyx lobes 4, stipitate, with an ovate to lanceolate limb on a narrow stipe-like basal portion.....Amphidasya spathulata
2'. Calyx lobes 4, nartrowly triangular to triangular, elliptic, oblanceolate, ligulate, or obovate, without a stipe-like basal portion.
3. Leaf blades oblanceolate to obovate, widest above the middle, at base acute to acuminate.
4. Calyx lobes at anthesis 15-24 mm long, linear to narrowly oblanceolate, acute to acuminate; stipules with the stipule body (i.e., the undivided basal portion) 2-12 mm long...Amphidasya ambigua
4. Calyx lobes at anthesis 6-15 mm long, narrowly triangular to narrowly oblanceolate, narrowly ligulate, obovate, or spathulate; stipules with the stipule body 1-4 mm long.
5. Inflorescences subsessile; calyx lobes acute to acuminate.....Amphidasya longicalycina
5'. Inflorescences with peduncles 0.5-2 cm long; calyx lobes acute to obtuse, rounded, or truncate.
6. Stipule lobes 5-13 mm long; western Colombia to Amazonian Peru....Amphidasya colombiana
6'. Stipule lobes 4-5.5 mm long; Sierra de la Neblina, Venezuela....Amphidasya neblinae
3'. Leaf blades elliptic, elliptic-oblanceolate, narrowly elliptic, elliptic-oblong, or ovate, widest variously below, at, or just above the middle, at base truncate, obtuse, rounded, cuneate, or acute but not or only shortly acuminate along petiole;
7. Corolla tube ca. 8 mm long; stipules with the stipule body (i.e., the undivided basal portion) 0.5-2 mm long and with 1-3 lobes....Amphidasya amethystinae
7'. Corolla tube 11-42 mm long (but unknown in Amphidasya brevidentata); stipules with the stipule body 1-15 mm long and with 4-11 lobes.
8. Stipules with the stipule body 2 or more times as long as the lobes....Amphidasya brevidentata
8'. Stipules with the stipule body about half as long or less as the lobes.
9. Corolla tube 11-15 mm long; calyx lobes at anthesis oblanceolate, obovate, or spathulate, 0.8-4 mm wide.
10. Leaves with secondary veins 10-15 pairs; corolla tube 13-15 mm long....Amphidasya colombiana
10'. Leaves with secondary veins 16-18 pairs; corolla tube 11-11.5 mm long....Amphidasya intermedia
9'. Corolla tube 11-15 mm long; calyx lobes at anthesis oblanceolate, obovate, or spathulate, 0.8-4 mm wide.
11. Calyx lobes at anthesis 9-10 mm long; corolla lobes smooth on the margins and adaxial surfaces.....Amphidasya umbrosa
11'. Calyx lobes at anthesis 9-19 mm long; corolla lobes markedly verruculose on the margins and adaxial surfaces, sometimes these projections giving the appearance of laciniate.
12. Corolla tube 36-40 mm long; eastern and central Panama.....Amphidasya panamensis
12'. Corolla tube 25-30 mm long; northwestern South America.
13. Corolla in bud acute to acuminate at apex; leaves with secondary veins 10-16 pairs.....Amphidasya bullata
13. Corolla in bud truncate at apex; leaves with secondary veins 22-30 pairs.....Amphidasya elegans