Name and species circumscription
Austrocactus praecox is the name accepted in Plants of the World Online, checked on 10 October 2026. [2-WWW]
A short stem and hooked spines
The plant usually has one upright, shortly cylindrical stem, 5–7 cm long and 2.5–3.5 cm in diameter. The epidermis is dark green to blackish green. Seven to nine ribs divide into rounded, blunt tubercles. Shortly oval areoles have very sparse, short, pale felt. [Böhnert et al. 2025, p. 401]
There are 1–4 central spines. One or two point outwards, while the others may be arranged in pairs. They are smooth to finely hairy and hooked. Up to ten radial spines are translucent, needle-like and arranged roughly in pairs. Spine appearance needs to be assessed together with the small, usually solitary stem. [Böhnert et al. 2025, p. 401]
A pastel flower and mature fruit
The funnel-shaped flower is around 4 cm long and the same in diameter. The tepals are lanceolate and pointed, pale yellow to pale pink. The pink to crimson style ends in 11–13 purple stigma lobes. The green pericarpel has scales, loose white hairs and long brown bristles along its upper margin. [Böhnert et al. 2025, p. 401]
The fruit is oval, dull dark green, around 10–13.5 × 14.5–16 mm, with bristle-like hairs and a small amount of white wool. It dries and opens from the base. The brownish-black seeds are slightly curved, around 2 × 1.5 mm. Features distinguishing the species from the small A. ferrarii include a solitary upright stem and a funnel-shaped flower with lanceolate tepals, compared with the clumping growth form and bell-shaped flower of that species. [Böhnert et al. 2025, p. 394, 399, 401]
La Payunia and uncertain historical specimens
The revision's confirmed range includes southern Mendoza, in the Malargüe department, near the boundary of La Payunia reserve. Plants grow in fissures in volcanic rocks. The species was described in 2020, and the 2025 revision reassessed its features and position in the group of local endemics with purple stigmas. [Böhnert et al. 2025, p. 394, 401]
Two historical specimens from Agua del Sapo may have belonged to A. praecox. Their condition prevented certain identification, and searches for living plants at this site were unsuccessful. The identity of these specimens and the species' presence at this locality remain unconfirmed. [Böhnert et al. 2025, p. 401]