Paracorynanthe is closely related to Hymenodictyon; these genera share a woody, sometimes deciduous habit; interpetiolar, triangular, often deciduous stipules; cymose, bracteate inflorescences that are terminal and often also produced in the uppermost leaf axils; bisexual flowers with 5 calyx lobes, corolla lobes, and stamens; funnelform corollas with the lobes valvate in bud; rather small, ellipsoid, lenticellate, capsular fruits with loculicidal dehiscence; and one to numerous flattened, winged seeds per locule. Some species in both genera characteristically have a pair of petaloid, long-stipitate bracts borne at the base of the inflorescence. These are generally pale green to white or sometimes pink. Razafimandimbison & Bremer (2006) revised these genera, and found them together to comprise the tribe Hymenodictyeae which is closely related to Naucleeae.
Paracorynanthe differs from Hymenodictyon as well as the other Rubiaceae in Madagascar in its unusual corollas, which have each lobe ornamented at the tip by a prolonged appendage that comprises a pilose stipe 3-4 mm long that bears a black globose club. The inflorescences of Paracorynanthe are rounded or corymbiform in general shape, while in Hymenodictyon the inflorescences or at least the axes are often spiciform. The ovaries of Paracorynanthe have 1-2 ovules per locule, while those of Hymenodictyon have 2-40 ovules per locule. The bark of Paracorynanthe characteristically falls in large plates or plaques.