Autor: Cárdenas

Genus honouring the Argentine botanist Alberto Castellanos (1896-1968). See portrait above, public domain.
Monospecific genus of treelike plants, branching from the base, with constricted cylindrical stems. Vegetative shoots have 9 ribs, grey areoles, brown spines; long gray to brown bristles appear along the flowering stems.
Flowers nocturnal, self-sterile, bell-shaped, scaly and felted, purple red, pollinated by bats (Glossophaga soricina). Fruits globose, greenish yellow with a dark yellow pulp, which it is said by Backeberg (1976) to be exceptionally poisonous, keeping the remains of dried perianth. Seeds reddish brown to black, rough. Dispersal takes place by bats (.Sturnira lilium).
The monotypic genus Castellanosia lives throughout the Rio Caine, to the southwestern Bolivian Chaco, on more or less inclined slopes, in dry valleys covered with woodlands dominated by trees like Gochnatia palosanto as well as Neoraimondia herzogiana, from 530 m up to 2330 m in altitude, together with many other cacti (Blossfeldialiliputana, Cereus hankeanus, Cleistocactus candelilla, Gymnocalyclum pflanzli, Harrisia tetracantha, Parodia columnaris, Pereskia diaz-romeroana, P. sacharosa, Pfeiffera ianthotele, Weingartia neocumingii subsp. pulquinensis) and succulents, epiphytic or terrestrial Orchidaceae and Bromeliaceae (Deuterocohnia longipetala). The presence of lichens demonstrates a high humidity.
Bolivia (Cochabamba, Chuquisaca, Santa Cruz, Tarija), Paraguay (Alto Paraguay, Boqueron, Concepcion).

Currently only one recognised species:
– Castellanosia caineana* Cárdenas 1951

References: "TAXONOMY of the CACTACEAE" -  ISBN 978-84-617-3723-9 (Vol. 1)