Calyptrochilum is a genus of flowering plants from the orchid family Orchidaceae[2] native to tropical Africa, with one species extending into Brazil.

[4] The original describers of Ossiculum, P.J.Cribb & Laan, noted that the genus closely resembled Calyptrochilum in terms of floral morphology.

In 1986, Gasson and Cribb (1986) found the leaf structure of Ossiculum and Calyptrochilum to possess shared characteristics that did not belong to other genera in the Angraecinae.

These findings were confirmed in 2006 by Carlsward et al., but O. aurantiacum remained separate from Calyptrochilum because of several of its own distinctive features, among them its bright golden flowers.

Finally, in 2018, Stévart, M.Simo & Droissart combined the previous morphological and cytological data with genomic information, cementing the position of the former monotypic genus within Calyptrochilum.