Name and species circumscription
Austrocactus occidentalis is the name accepted in Plants of the World Online, checked on 10 October 2026. Felix F. Merklinger described the species in the 2025 revision. [2-WWW] [Böhnert et al. 2025, taxonomic record and species description in the 2025 revision]
Branching and spines
Stems are usually spreading, sometimes upright, cylindrical, up to 30 cm long and 6 cm in diameter. The plant can form a clump, and adventitious roots occur rarely. Around nine ribs divide into small, flat tubercles. Oval areoles are strongly woolly on young growth and later have grey felt. [Böhnert et al. 2025, p. 411]
Three or four central spines are arranged roughly in a cross. They are smooth and straight, sometimes with one ending in a hook. Ten to twelve radial spines spread in pairs. These are smooth needles, some translucent. Stem number and size vary greatly between plants. [Böhnert et al. 2025, p. 411]
A red stigma and dense fruit covering
The broadly funnel-shaped to bowl-shaped flower is around 6 cm long and 5.5 cm in diameter. The broad, spatulate tepals are bright yellow at the base, and darker yellow to brownish red above. The style is usually red, rarely pale. The roughly twelve stigma lobes are dark red, exceptionally yellow. [Böhnert et al. 2025, p. 411]
The pericarpel is green and densely covered with brown wool and bristles. The oval fruit, around 1 × 1.7 cm, retains a dense covering and numerous bristles. On ripening, it dries and opens irregularly. Seeds are brownish black, curved and around 2.5 × 2 mm. The dense fruit covering links the species to section Coxiani. [Böhnert et al. 2025, p. 407, 411]
Andean foothills and the extent of variation
The revision places the species in western Chubut and the far north of Santa Cruz, at the Andean foothills. The description uses plants from many sites, including near Esquel and Tecka. The precise range presented here comes from this revision. The main POWO entry is restricted to Chubut. [Böhnert et al. 2025, p. 411] [2-WWW]
Several specimens were included in the genomic analyses to cover variation in growth form, stem number and stem size. The plants formed a shared lineage close to A. coxii. The revision retains one species. Any future separation of its forms would require testing whether differences in appearance coincide with a persistent genetic and geographical division. [Böhnert et al. 2025, p. 389–390, 411]