Name and species circumscription
Austrocactus elegans is the name accepted in Plants of the World Online, checked on 10 October 2026. Tim Böhnert described the species in the 2025 revision. The detailed description below concerns populations around Tromen analysed in that study. [2-WWW] [Böhnert et al. 2025, taxonomic record and species description in the 2025 revision]
Stem, tubercles and spines
The plant usually has one stem and sometimes branches. The stem is upright, spherical to elongated, dull green, up to 8 cm high and 6 cm in diameter. Around nine ribs divide into conical tubercles. Round areoles measuring around 8 × 8 mm have a felted covering. [Böhnert et al. 2025, p. 403]
Usually four central spines are arranged roughly in a cross and project outwards. The lower one is longest. The spines have a fine surface coating and are straight to curved. Eight, sometimes ten radial spines spread in pairs. They are smooth and straight, and some remain translucent. The low growth form and spine arrangement distinguish the species from the more robust A. decorus. [Böhnert et al. 2025, p. 401, 403]
The flower and how the fruit opens
The narrowly funnel-shaped flower measures around 3.5 cm long and 4.5 cm in diameter. The tepals are spatulate with a pointed tip. Their lower part is pastel-coloured or lemon-yellow, and the upper part often apricot to brownish red. The whitish style ends in around ten pale yellow stigma lobes. The green pericarpel bears scales, white hairs and fine bristles. [Böhnert et al. 2025, p. 403]
The fruit is slightly elongated to almost spherical, around 1.5 cm in diameter, green, with white wool and few bristles. It splits lengthwise after drying. The seeds are dark grey, curved and around 2.5 × 2 mm. Longitudinal fruit opening is retained from the direct species description in the revision. [Böhnert et al. 2025, p. 403]
Volcanic rocks and the scope of identification
The revision's material comes from the northern and western sides of Tromen volcano in the Chos Malal and Pehuenches departments of Neuquén Province. Plants occur among volcanic rocks, within Reserva Provincial Tromen and beyond its boundaries. Genomic samples came from populations north of the reserve. [Böhnert et al. 2025, p. 403]
In the southern part of the reserve, populations potentially resulting from crosses between A. elegans and A. decorus were observed. The authors treat their origin as a question for further analysis. The detailed sites of A. elegans in the revision cover a narrower area than the POWO range, which also includes Chile and Mendoza. These scopes remain assigned to their respective sources. [Böhnert et al. 2025, p. 403] [2-WWW]