Key points to the genera of Melinidinae:
1. Lower and upper glume awned	Chaetium
1′. Lower and upper glume muticous	2
2(1′). Plants andromonoic; inflorescences deciduous as a whole at maturity; rachis broadly winged, foliaceous, and folded transversely to form a capsule	Thuarea
2′. Plants not andromonoic; inflorescences not early deciduous; rachis triquetrous, subcylindric, or broadly winged	3
3(2′). Upper anthecium smooth, shiny, and coriaceous to membranous or hyaline; apex of the upper anthecium muticous	4
3′. Upper anthecium longitudinal or transversely rugose, with simple or verrucose papillae all over its surface, coriaceous to crustaceous; apex of the upper anthecium mucronate, crestate, or awned	10
4(3). Spikelets adaxial	5
4′. Spikelets abaxial	6
5(4). Upper anthecium not stipitate, nearly as long as the upper glume and the lower lemma; upper glume and lower pilose, without transverse veinlets	Leucophrys
5′. Upper anthecium stipitate, shorter than the upper glume and lower lemma; upper glume and lower lemma glabrous, with transverse veinlets	Eccoptocarpha
6(4′). Plants annual; inflorescences digitate	Yvesia
6′. Plants perennial; inflorescences not digitate	7
7(6′). Upper anthecium falling with glumes and lower anthecium, not early deciduous, and laterally compressed	Melinis
7′. Upper anthecium early deciduous, without the bracts of the spikelet, dorsiventrally compressed	8
8(7′). Inflorescence racemose, not pyramidal, with spikelets secund on short pedicels	Moorochloa
8′. Inflorescences lax, pyramidal, with spikelets not secund on long, capilliform pedicels	9
9(8′). Inflorescence without glandular hairs; lower glume absent or vestigial; upper anthecium readily deciduous	Tricholaena
9′. Inflorescence with glandular hairs; lower glume ⅘ to nearly as long as the spikelet; upper anthecium not readily deciduous	Batochloa
10(3′). Spikelets with a globular bead-like callus at its base	Eriochloa
10′. Spikelets without a globular bead-like callus at its base	11
11(10′). Upper anthecium longitudinally rugose, with flat macrohairs at the apex	12
11′. Upper anthecium transversely rugose to slightly or strongly reticulate, without flat macrohairs at the apex	13
12(11). Spikelets arranged in racemose inflorescences. Endemic to the Caribbean	Scutachne
12′. Spikelets dispersed in open, and no racemose inflorescences. Brazil	Rupichloa
13(11′) Inflorescences lax, pyramidal, with third-order branches present	Megathyrsus
13′. Inflorescences racemose or lax, but only with first- and second-order branches	Urochloa