Echinomastus acunensis W. T. Marshall, Saguaroland Bull. 7: 33. 1953; Neolloydia erectocentra (J. M. Coulter) L. D. Benson var. acunensis (W. T. Marshall) L. D. Benson

Stems 4-16.5(-27) × 4-9 cm; ribs 21; areoles 15-19 mm apart along ribs. Spines 13-16 per areole, purplish pink or nearly white with brown tips; radial spines 12-15 per areole; abaxial (shortest) radial spine 11-20 × 0.42-0.59 mm; adaxial and lateral (longest) radial spines 22-37 mm; central spines ascending, (1-)2-3(-4) per areole, 19-44 × 0.6-0.8 mm, longest adaxial central spine curved toward apex of plant, sometimes slightly so; abaxial or only central spine 25-35 mm. Flowers 3.6-6 × 4-9 cm; inner tepals pale to bright rose-pink, proximally blotched orangish brown, chestnut, maroon, or greenish brown, (2-)3-4.3 × 0.7-1.8 cm; stigma lobes red to brownish red, papillae red to green. 2n = 22.

Flowering Mar-Apr; fruiting Apr-May. Arizona Upland Subdivision of Sonoran desert scrub, low gravelly hills, bajadas, and rocky hilltops, igneous substrates; 400-800 m; Ariz.; Mexico (Sonora).

Echinomastus erectocentrus var. acunensis is in the Center for Plant Conservation’s National Collection of Endangered Plants.