Etymology: The specific epithet is derived from the extremely thin almost transparent leaflets. Historical notes: Distinguishing features: Zamia hymenophyllidia is most similar to Z. melanorrhachis. Both species are unique in the cycads with the presence of extremely long thin peduncles (to 30 cm long and 1-3 mm diam) terminated by very small pollen cones (1-3 cm long and 1-3 mm diam). Zamia hymenophyllidia has membranous, elliptic, long acuminate leaflets in contrast to the papyraceous, lanceolate, generally acute leaflets of Z. melanorrhachis. The leaflets margins of Z. hymenophyllidia are generally entire and if toothed, the teeth are inconspicuous and apical. In contrast, Z. melanorrhachis has well-developed marginal teeth. Living plants of Z. melanorrhachis have a dark purple to black petiole and rachis, a feature not found in Z. hymenophyllidia. Distribution and habitat: Only three small populations are known in Southeastern Amazonian Colombia. Zamia hymenophyllidia grows as an understory plant in lowland primary rainforest. Conservation: Zamia hymenophyllidia was discovered only in the past three years from three small populations. The plants are reproductive and produce seeds and seedlings. Little is known about its biology and distribution but the paucity of collections indicates that it is rare. Not yet listed in 1997 IUCN Red List of Threatened Plants. Description:
Stem subterranean and tuberous, 2-4 cm diam. Cataphylls triangular basally, linear-lanceolate apically, membranaceous, 2-3 cm long, 0.5-1 cm wide. Leaves 2-5, erect, oblong, 30-70 cm long; petiole terete, to 35 cm long, armed with very small prickles; rachis terete, usually unarmed, to 20-35 cm long, 4-10 pairs of leaflets. Leaflets membranaceous, elliptic to elliptic-lanceolate, long acuminate apically, cuneate to oblique basally, margins entire or rarely with a few diminutive apical teeth, 12-15 cm long, 1-2 cm wide. Pollen cones brown, ovoid, 1-3 cm long, 0.1-0.3 cm diam.; peduncle 10-30 cm long; microsporophylls with both abaxial and a few (1-3) adaxial sporangia. Seed cones dark red-brown, cylindrical to ovoid- cylindrical, to 5 cm long, 3-4 cm diam; peduncle to 15 cm long, 0.5 cm diam. Seeds red orange-red, 1-1.2 cm long, 0.5-0.8 cm diam.
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