Pterocactus

A low geophyte with grey-brown, globose or pear-shaped segments. In DNA studies it belongs to the southern lineage of the genus with Pterocactus neuquensis and Pterocactus hickenii. Its microscopic papillae are curved.

A southern geophyte with globose to pear-shaped segments and flattened spines. Its identification history is linked to a French expedition observing the 1882 transit of Venus, while current studies reveal variation in chloroplast DNA.

A species with cylindrical segments and relatively long, flat central spines. In the chloroplast analysis it diverged early in the lineage containing Pterocactus tuberosus and several other members of the genus.

R.Kiesling, E.Sarnes & N.Sarnes

A species from San Juan in Argentina with cylindrical segments, woolly areoles and short central spines. Its cuticle shows distinct, regular striations visible in electron microscopy.

A southern species of Argentina and Chile, with globose to pear-shaped segments and conspicuously spreading spines. The material studied had 154 chromosomes, corresponding to fourteen basic sets.

A species endemic to San Juan, with cylindrical segments and woolly areoles. Stem-surface studies described curved papillae, while DNA quantity corresponded to a low ploidy level compared with some relatives.

A species from Neuquén, distinguished by lateral flowers. Its globose or pear-shaped segments have short spines, and chromosome number in the material studied was 99.

A species of Mendoza and San Juan, with tuberculate segments, woolly areoles and lateral flowers. In the chloroplast analysis it belongs to a different main lineage from Pterocactus neuquensis, which also flowers laterally.

A geophyte from a broad belt of Argentina, with thin cylindrical segments and a thickened underground part. Its winged seeds germinate under warm, well-hydrated conditions, while established seedlings can undergo periods of substantially reduced growth.

A species with cylindrical segments and terminal flowers, associated with southern Monte. In the 2009 pollen paper its name was written as Pterocactus valentinii. Current nomenclature accepts the ending valentini.