Six new Guianan species of Ouratea Aubl. (Ochnaceae) are described: two from Guyana, O. superimpressa Sastre and O. takutuensis Sastre; one from Guyana and Suriname, O. jansen-jacobsiae Sastre; one from Suriname, O. sipaliwiniensis Sastre; and two from French Guiana, O. retrorsa Sastre and O. miniguianensis Sastre. Ouratea superimpressa differs from O. cataractarum Sandwith from Guyana by its lanceolate leaves, sunken secondary and tertiary veins and smaller flowers, and from O. impressa (Tiegh.) Lemée from French Guiana and Brazil (Amapá) by its branched inflorescences, and young fruits with some persistent sepals. Ouratea takutuensis differs from O. culminicola Maguire & Steyerm. from Venezuela (Bolivar) by its membranaceous leaves with denticulate margin and two types of secondary veins. Ouratea jansen-jacobsiae differs from O. occultinervis Sastre from French Guiana and Suriname, by its subequal secondary veins, plane and reticulate secondary and tertiary veins, and fruits with a plane and not spathulate carpophore. Ouratea sipaliwiniensis differs from O. melinonii (Tiegh.) Lemée from French Guiana by its plane leaf-blade with slightly undulate margin and hardly visible secondary veins. Ouratea miniguianensis differs from O. guianensis Aubl. from the coastal Guianan zone of Venezuela to Brazil, by its smaller leaves (10-15.5 cm long vs 14.5-32 cm), and fruits with a conical torus of 15 mm high. Ouratea retrorsa differs from O. miniguianensis by its leaf-blade with the retrorse apex and hardly visible secondary veins.
Ochnaceae, Ouratea, Guyana, Suriname, French Guiana, biogeography, new species