Mallotus concinnus Airy Shaw, M. havilandii Airy Shaw, M. insularum (Airy Shaw) Slik, and M. miquelianus (Scheff.) Boerl. are very similar in appearance, with opposite leaves of which one large and elliptic, and the other reduced and more or less obcordate. However, a detailed look revealed enough differences to regard them as distinct species.

Euphorbiaceae, Hancea, Mallotus
Blumea: Biodiversity, Evolution and Biogeography of Plants

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Naturalis journals & series

van Welzen, P.C, Sierra, S.E.C, Gebraad, M.J.H, & Kulju, K.K.M. (2006). The distinction of five Mallotus species formerly in section Hancea (Euphorbiaceae). Blumea: Biodiversity, Evolution and Biogeography of Plants, 51(2), 367–372.