Name and species circumscription
Austrocactus ferrarii is the name accepted in Plants of the World Online, checked on 10 October 2026. [2-WWW]
A low clump on rocky ground
The stems are short, spreading and cylindrical, usually around 4 cm, sometimes up to 6 cm long, and 2.5–3 cm in diameter. They are light olive to brownish green. Nine or ten ribs divide into flat, rounded tubercles. Oval areoles, around 3 × 6 mm, are initially covered with cream-coloured felt. [Böhnert et al. 2025, p. 399]
An areole usually bears one, sometimes two central spines. They are deflected, finely hairy and sometimes slightly curved. Six or seven needle-like radial spines spread irregularly. The arrangement of small stems in a clump and the bell-shaped flowers distinguish this species from the more upright A. diamantinus and A. praecox. [Böhnert et al. 2025, p. 394, 397, 399, 401]
Flower, fruit and seed
The flower is around 3.5 cm long and similar in diameter. The tepals are spatulate, brownish red outside and pale yellow inside, with a pink tint in their upper part. The style is light yellow to pink, and the roughly ten stigma lobes are dark purple. The dark green pericarpel bears bristles and hairs. [Böhnert et al. 2025, p. 399]
The almost spherical fruit is around 1 cm in diameter and dark green. It is covered with bristles and hairs. As it ripens, it dries and opens irregularly from the base. The blackish-brown, curved seeds measure around 2 × 1.5 mm. [Böhnert et al. 2025, p. 399]
Sierra del Tontal and the northern edge of the genus
The revision's confirmed sites lie in northern Mendoza, in the Las Heras department, at elevations of 2400–2900 m. The plant occupies gravel beds and rock fissures of the Sierra del Tontal. In this study, it is the northernmost known member of Austrocactus. The possibility of sites in neighbouring San Juan Province follows from the mountain range continuing there, but remains the authors' prediction. [Böhnert et al. 2025, p. 399]
Genomic data link A. ferrarii to A. diamantinus in a group of local Andean endemics with purple stigmas. Its position in the group gives its relationships, while species distinctness also rests on growth form, flowers and geographical separation of sites. [Böhnert et al. 2025, p. 394, 399]