Autor: Backeberg & Knuth
• ETYMOLOGY
“Spiny calyx”, referring to the main morphological characteristic of the genus.
• DESCRIPTION
A genus of usually single-stemmed plants, globose to lightly elongated, with the apex depressed. Ribs acute, more or less tuberculate, spines usually straight, aciculate to subulate.
Flowers diurnal, subapical (main difference with Echinopsis sensu lato), funnel-shaped to campanulate, white, pink or red, with floral tube formed by thorny scales (hence its name), pollinated by bees or sphingideae, more rarely by hummingbirds. Fruits hard, spherical, with persistent scales, with a vertical dehiscence. Seeds brownish to black, papillose, with the hilum depressed, scattered by rainwater (hydrochory).
• HABITAT
The genus Acanthocalycium grows in northwest Argentina, at an altitude between 300 m and 3300 m, on sloping, arid, rocky ground, among grasses, bushes, in the shade of shrubs or in full sun, in valleys or mountainous hillsides.
• DISTRIBUTION
Argentina (Catamarca, Córdoba, La Rioja, Salta, San Luis, Tucumán).
Currently 5 recognised species:
– Acanthocalycium ferrari* – Rausch 1976 (=A. variiflorum nom. invai.)
– Acanthocalycium glaucum* – F. Ritter 1964
– Acanthocalycium klimpelianum* – (Weidl. & Werderm.) Backeb. 1935 (= A. peitscherianum)
– Acanthocalycium spiniflorum* – (K.Schumann.) Backeberg 1935 (= A. violaceum)
– Acanthocalycium thionanthum* – (Spegazzini) Backeberg 1935
References: “TAXONOMY of the CACTACEAE” – ISBN 978-84-617-3723-9 (Vol. 1)