order of dicotyledonous flowering plants comprising the family Didymelaceae, with one genus (Didymeles) and two species, both of which are trees of Madagascar with very simple, primitive flowers. The plants are so distinctive that close relatives are nonexistent, as is reflected in the ordinal status given the group. The flowers are separately male and female, on different plants. The male flower consists of two anthers (pollen sacs) without stalks plus one or two small scales attached just below the anthers. The female flower consists of as many as four scales plus a single cylindrical carpel (ovule-bearing structure) with a large, obliquely situated pollen-receptive surface (stigma) and a single ovule.

The fruit is a drupe, large, one-seeded, fleshy, and plumlike, with a lateral groove. In addition to the primitive flowers, the wood also exhibits many primitive features—among others, water-conducting cells with ladderlike sculpturings on the walls (scalariform pitting); and sclereids (fibre cells) with large, distinctly bordered pits in the wall.