Anonymous (no date): Information source: publication in preparation.
CMT VIII 2011: Mantalania is quite distinctive in the Rubiaceae, where it is characterized by its habit as an unbranched or little-branched shrub or small tree with the leaves clustered at the stem apices where the internodes are hardly developed; its relatively large narrow leaves produced in whorls of 3-6; its relatively large triangular stipules; its axillary cymose inflorescences with several large flowers borne on well developed pendulous peduncles; its funnelform to salverform, at leasst frequently white corollas with the lobes 6-10 and contorted in bud; its ovaries that are 1-locular with parietal placentation; and its large fleshy fruits with the numerous seeds embedded in pulp. The flowers are apparently bisexual, and the fruits become relatively large and apparently brown at maturity. De Block et al. (2006) presented excellent color photos of the flowers and leaves of Mantalania longipedunculata.
Pseudomantalania is very similar to Mantalania, and in general replaces it at higher elevations. These genera are distinguished by several characters as outlined in the key below; their relationship does not seem to have been studied in detail since the work of Leroy (1974). Pseudomantalania macrophylla was originally suggested to be a species of Mantalania by Capuron, but Leroy first formally described this species and separated it from Mantalania.
Leroy (1974) recognized 2 species of Mantalania and another specimen or plant that he called "Mantalania cf. capuronii", and described in detail and illustrated. This provisionally identified specimen was Capuron 22832 SF [i.e., Service Forestier 22832 (leg. Capuron)] from "le lit de la Mananadriana près de son embouchure (entre Sahasoa et Vahibe, au Sud de Mananara)". Leroy described Mantalania capuronii based on one specimen with fruit, while the specimen he called "Mantalania cf. capuronii" had only flowers. These two specimens differ in several characters, as outlined in the key below, and perhaps in geographic range. These two groups of plants were also provisionally separated, following Leroy, by De Block & Davis (2006). The fruits are now documented for "Mantalania cf. capuronii" and are similar to those of Mantalania capuronii (Rabenantoandro et al. 940); the flowers of Mantalania capuronii are apparently still unknown.