First person to use this name on MO: Nathan Wilson
This species was originally described as T. titans from Florida, U.S.A. (Bigelow and Kimbrough, 1980), and was described again as T. cystidiosum from Mexico (Cifuentes and Guzmán, 1981). Later, Courtecuisse (1985) renamed T. cystidiosum as T. cifuentesii because the former was a homonym, and Singer (1990) synonymized it with T. titans. Macro- cybe titans is mainly distinguished macroscopically by the distinctly squamose stipe surface, and microscopically by the numerous, refractive pseudocystidia. This is the fungus previously reported under the name of T. pachymeres (Berk. & Broome) Sacc., by Baker and Dale (1951: 94, pl. lg) and Pegler (1983: 111, pl. 3D). The habit of the Costa Rican collections of growing from active Atta ant gardens is distinctive. Except for the presence of cheilocystidia on some of the Costa Rican collections, they were indistinguish- able from other collections of M. titans.