1	Upper side of leaf lamina clearly densely pubescent	G. gabonicum
–	Upper side of leaf lamina sparsely pubescent to glabrous	2
2	Upper side of midrib glabrous	G. glabrum
–	Upper side of midrib to sparsely pubescent	3
3	Connective of the stamens flattened or discoid in shape (West Africa)	G. oliveri
–	Connective of the stamens tongue-shaped or lobulated (Central and East Africa)	4
4	Tree 2–5 m tall, stamens in hermaphrodite flowers 4–5; mature monocarps 2.5 × 4.2 cm in diameter (coastal Gabon and Republic of Congo)	G. littorale
–	Tree up to 45 m lower limit of height, stamens in hermaphrodite flowers 5–10; mature fruits 7.2 × 16.4 cm in diameter	5
5	Secondary veins ≤ 12 (Central Africa, widespread)	G. suaveolens
–	Secondary veins ≥ 14 (Tanzania, Eastern Arc Mountains)	G. usambaricum