Herbaceous climber or trailer with dioecious sex system. The leaves are simple, petiolate, the blade is unlobed, lanceolate with subcordate to sagittate base. The tendrils are simple. Flowers are small, male flowers are produced in corymbs, female flowers solitary. The receptacle-tube is narrowly campanulate with five lanceolate sepals. The five petals are fused at the base, oblong-lanceolate, entire. The three stamens are inserted near the mouth of the tube, filaments are lacking. Two anthers are bithecous, one monothecous. The thecae are curved and contain tricolporate, perforate, small pollen (polar axis c. 43 µm, equatorial axis c. 45 µm (Khunwasi 1998)). The ovary is lanceolate with two placentae and many, horizontal ovules. The style is robust, inserted in the center of a circular disc and carries a solitary, bilobed, fleshy stigma. The fruit is oblong, slightly pubescent with oblong, compressed, verrucous seeds.
The only species grows in humid places of the Brazilian states of Rio de Janeiro and Minas Gerais.
Phylogenetically, the genus is places in the tribe Coniandreae and seems to be close to Apodanthera but its exact relationships are still unresolved (Schaefer et al. 2009).
Melothrianthus smilacifolius (Cogn.) Mart.Crov., Notul. Syst. (Paris) 15: 60. 1955.
Gomes-Klein, V. L. 1996 . Cucurbitaceae do estado do Rio de Janeiro: subtribo Melothriinae E.G.O. Muell et F.Pax. Arq. Jard. Bot. Rio de Janeiro 34: 93-172.
Khunwasi, C. 1998. Palynology of the Cucurbitaceae. Doctoral Dissertation Naturwiss. Fak., University of Innsbruck.
Schaefer, H., Heibl, C., and S.S. Renner. 2009. Gourds afloat: a dated phylogeny reveals an Asian origin of the gourd family (Cucurbitaceae) and numerous oversea dispersal events. Proceedings of the Royal Society B 276: 843-851.