Name and species circumscription
Austrocactus aonikenkensis is the name accepted in Plants of the World Online, checked on 10 October 2026. [2-WWW]
Growth form and stem surface
The plant usually has one stem and branches less often. The stem is shortly cylindrical or stoutly columnar, creeping or upright. The revision usually gives a height of 10–20 cm, sometimes up to 40 cm, with a diameter of around 6 cm. The epidermis is dark olive to dull green. There are 8–11 ribs. They divide into strong tubercles, thickened around slightly sunken areoles. [Böhnert et al. 2025, p. 394]
The oval areoles initially bear short, cream-coloured felt. The one to four central spines cannot always be clearly distinguished from the others. They point outwards or upwards. Around 10–12 radial spines lie close to the stem surface, often almost in pairs. Spines may have fine hairs or be partly translucent. The combined spine orientation and stem proportions change the appearance of plants between sites. [Böhnert et al. 2025, p. 394]
The flower, fruit and seeds
The funnel-shaped flower is around 5 cm long and 6 cm in diameter. The broad, spatulate tepals end in a distinct point and are pink to magenta. The style is red or purple, and the stigma has 9–11 pinkish-purple or purple lobes. The pericarpel, the covering around the ovary at the flower base, is dark green to olive, grooved and sparsely covered with wool and bristles. [Böhnert et al. 2025, p. 394]
The fruit is flattened-spherical or oval, around 14 × 18 mm, dark olive to dark green. Its areoles bear wool and brown hairy bristles. The ripe fruit dries and opens from the base. The black, dull seeds resemble a comma and measure around 2.2–2.5 × 1.3–1.5 × 1 mm. [Böhnert et al. 2025, p. 394]
Range and variation
The revision places the species on sandy and gravelly plains of Santa Cruz Province, from the coast to the Andean foothills, and in the Río Senguer and Sarmiento departments of Chubut Province. Its extensive range corresponds to considerable variation in growth form. Along with A. bertinii, it is among the most widely distributed members of the genus. [Böhnert et al. 2025, p. 396]
Various forms were included in the genomic analysis, but their appearance did not correspond to clear subgroups on the tree. Support for a shared species lineage was strong in the maximum-likelihood analysis and weaker in the coalescent analysis. The revision retains them in one species. Further separation of these forms would require combining an extensive morphological analysis with a larger genetic sample. [Böhnert et al. 2025, p. 396]