Glabrous succulent trees or shrubs, sometimes epiphytic, unarmed. Leaves opposite, petiolate, entire, with venation not lineolate and mostly not visible, without domatia, fleshy and drying thickly coriaceous; stipules interpetiolar, oblanceolate to obovate, in bud erect and flatly appressed, caducous. Inflorescences terminal, umbelliform or corymbiform and few-flowered or flowers solitary, pedunculate to subsessile, ebracteate or bracts reduced. Flowers pedicellate, bisexual, homostylous, protandrous, nocturnal, large, showy, fragrant; hypanthium ellipsoid to cylindrical; calyx limb with short tube, lobes (4)5-6(7), without calycophylls; corolla salverform with well developed tube, white becoming yellowed with age, glabrous, lobes (4)5-6(7), triangular, in bud imbricated with 3 lobes external or sometimes convolute (C. valerioi), without appendices; stamens 5-6, inserted in corolla tube just below throat, anthers narrowly oblong and sometimes shortly bicaudate at base, basifixed, included, opening by longitudinal slits, without appendages; ovary 2-locular, with ovules numerous in each locule on axile placentas, stigma 1, shortly bilobed, partially exserted. Fruit capsular, oblong or cylindrical, septicidal from apex, woody, smooth, valves 2, the calyx limb deciduous; seeds numerous, flattened, small, fusiform to elliptic, marginally winged and entire to erose.

Key to the Species of Cosmibuena

1. Leaves 1-4.2 cm wide, obovate, obtuse to broadly rounded at apex, drying thickly coriaceous; plants drying red-brown; old stipules turning red; calyx limb divided to base; flowers solitary; capsules smooth; Costa Rica and Panama, 700-2300 m...C. valerioi

1. Leaves 2.4-16 cm wide, elliptic to obovate, obtuse or broadly rounded to acute at apex, drying coriaceous to subcoriaceous; plants drying green or gray-green; old stipules turning white; calyx limb truncate or partially to deeply lobed; flowers 2-9 in cymes; capsules smooth or lenticellate.

   2. Capsules 7.3-11.2 cm long; seeds 7-9 mm long (including the wing); leaves obtuse to broadly rounded at apex; Costa Rica to Peru, 0-500 m... C. macrocarpa

   2. Capsules 4.0-6.5 cm long; seeds 5-6 mm long (including the wing); leaves obtuse to acute at apex; southern Mexico to Bolivia, 0-2200 m.

      3. Calyx limb truncate to lobed, with its lobes if present shorter than or equal in length to its tube; leaves 3.6-16 cm wide; southern Nicaragua to Bolivia, 0-2200 m...C. grandiflora

      3. Calyx limb lobed with its lobes longer than its tube; leaves 3-8 cm wide; southern Mexico to northern Nicaragua, 0-500 m...C. matudae