Woody liana, 20-40 m long with dioecious sex system. The leaves are simple, petiolate, with broadly cordate-ovate, entire blade. Young plants have very conspicuous 4-verticillate basal leaves. The tendrils are bifid, to 15 cm long, inserted axillary, always with circular, peltate adhesive pads. The flowers are small, male flowers in erect, axillary spikes or racemes, female flowers solitary or in small groups. The receptacle-tube is shallowly cup-shaped. The five sepals are almost free, broadly obtuse-triangular. The five petals are broadly-obovate, almost free, reflexed, purple-red, densely covered with multicellular hairs. The three stamens are inserted near the center of the tube on short free filaments. Two anthers are bithecous (the thecae halfway fused), one is monothecous, creamy white, somewhat fleshy. The thecae are straight, oblong, the pollen small (polar axis c. 34 µm, equatorial axis c. 21 µm), tricolporate, striate (van der Ham 1999). Ovules many, pendent. The fruit is a cylindrical-clavate capsule, c. 20 cm long, ripening brown and opening with three valves. The seeds are compressed with finely verrucous, dull brown testa and the margin coarsely 8-9-spined, with broad circular membraneous wing, c. 5 cm in diameter.
The only species, Bayabusua clarkei, grows in lower montane forest (200-800 m a.s.l.) in Peninsular Malaysia.
Phylogenetically, Bayabusua is together with Alsomitra one of the earliest branching lineages of the family but its exact position remains unresolved (Schaefer & Renner 2011).
De Wilde, W.J.J.O. and B.E.E. Duyfjes. 1999. Bayabusua, a new genus of Cucurbitaceae. Sandakania 13: 1-16
Schaefer, H. and S.S. Renner. 2011. Phylogenetic relationships in the order Cucurbitales and a new classification of the gourd family (Cucurbitaceae). Taxon 60: 122-138.
Van der Ham, R.W.J.M. 1999. Pollen morphology of Bayabusua (Cucurbitaceae) and its allies. Sandakania 13: 17-22.