This species is characterized by rather small to medium-sized (for Amphidasya) leaves, well developed multi-laciniate stipules, calyx lobes 6-13 mm long, and corollas with the tube 35-40 mm long and the lobes 8-15 mm long. The leaves are characteristically oblanceolate to obovate, and tapered at the base to a short petiole. The secondary leaf veins are generally rather numerous, 15-25 pairs. The flowers are clustered closely, and usually many of them are open at the same time. The buds are acute at the tips. Amphidasya longicalycina shows notable variation in size of the vegetative structures and corollas in Central America. 

Centra American plants of Amphidasya longicalycina were included by the Flora of Panama (Dwyer, 1980) and the Flora Costaricensis (Burger & Taylor, 1993) within the circumscription of Amphidasya ambigua. However these are two distinct species, and Amphidasya ambigua can be separated by its more robust habit, larger stipules, and calyx lobes 15-24 mm long. Only Amphidasya longicalycina is so far known from Nicaragua through central Costa Rica. Plants of Amphidasya longicalycina from northwestern South America were included in Amphidasya ambigua also by Andersson (1991), along with several other species of the genus.