Houserock cactus, park hedgehog cactus

Pediocactus simpsonii var. (Engelmann) Britton & Rose paradinei (B. W. Benson) Halda; Pilocanthus paradinei (B. W. Benson) B. W. Benson & Backeberg

Plants unbranched. Stems subglo-bose to globose, 3-7.5 × 2.5-5.5(-8) cm; areoles circular to oval, villous. Spines smooth, thin and flexible, sometimes distinguishable as radial and central; radial spines 13-22 per areole, straight or curving irregularly, white, 20-25 × 0.2-0.3 mm; central spines 3-6 per areole, dense in mature plants, white to pale gray, straight, flexible, hairlike, 8-35 × 0.3 mm. Flowers 1.5-2.2 × 1.9-2.5 cm; scales and outer tepals minutely toothed or denticulate or entire and undulate; outer tepals brown midstripes with pale or white margins, oblanceolate, 8-20 × 3-6 mm; inner tepals light yellow to pink, oblanceolate, 15-20 × 4-6 mm. Fruits greenish yellow maturing to reddish brown, cylindric, 7-10 × 5-8 mm. Seeds black, 2.5 × 2 mm, papillate but not rugose.

Flowering spring. Gravelly limestone soils of pinyon-juniper, ponderosa pine, and grama grass communities; of conservation concern; 1500-2100 m; Ariz.

Pediocactus paradinei is endemic to the Kaibab Plateau region of northern Arizona.