Key to the genera of the Mcvaughia clade
1. Petals all bright yellow; pedicel straight in bud; anterior 7 (–9) stamens bearing fertile horseshoe-shaped anthers, the posterior 3 (–1) stamens represented by short staminodes bearing tiny, rudimentary, sterile anthers; ovary with only 1 locule developed; fruit 7–10 mm long, 4–5 mm in diameter, asymmetrical, proximally gibbous, distally sulcate; pollen 4 (5)-colporate.

1. Petals pink or white or lateral petals white and posterior petal yellow; pedicel circinate in bud; all 10 stamens fertile and ± alike, the anthers elongated, with parallel locules; ovary 3-locular, although not all locules necessarily contain ovules; fruit 9–28 mm long, 8–19 mm in diameter, symmetrical; pollen 3-colporate.

2. Stipules connate in intrapetiolar pairs, persistent; limb of outermost petal concave; connective of anthers enlarged and fleshy, often exceeding the apically rounded locules; filaments glabrous.

2. Stipules connate in interpetiolar pairs, caducous, leaving a large interpetiolar scar; limb of outermost petal conical-galeiform; connective of anthers slender, exceeded by extensions of the apically tapered locules; filaments densely hirsute.