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shiny leaf sandpaper plant, smooth sandpaper plant

sandpaper plant, Thurber's sandpaper plant

Habit Subshrubs or shrubs, bushy to moundlike, to 6 dm; branches of current season 11–37 cm. Shrubs, bushy to moundlike, to 10 dm; branches of current season 12–45 cm.

petiole 1–4 mm;

blade ovate, without marked size dimorphism, to 35 × 28 mm, base acute to obtuse, margins serrate to dentate, apex acute.

petiole absent;

blade ovate to elliptic, with marked size dimorphism, to 45 × 15 mm, much larger on main stems than on fertile branches, base acute to rounded, margins usually serrate or crenate, distal often entire, apex acute.



to 40-flowered.


slightly bilaterally symmetric through curvature along length of flower;

petals spatulate, 6–11 mm, claws postgenitally distally coherent, forming slitted corolla tube;

stamens exserted laterally through slits between petal claws.

conspicuously bilaterally symmetric;

petals spatulate, to 6.5 mm, claws postgenitally distally coherent, forming slitted corolla tube;

stamens exserted laterally through slits between petal claws.


= 46.

= 46.

Petalonyx nitidus

Petalonyx thurberi

Phenology Flowering Mar–Aug.
Habitat Sandy, gravelly, or rocky canyon slopes, arroyo bottoms, scrub.
Elevation 400–2200 m. [1300–7200 ft.]

Subspecies 2 (2 in the flora).

W. S. Davis and H. J. Thompson (1967) called attention to geographical variation in Petalonyx thurberi and distinguished subsp. gilmanii, which is restricted to washes in Inyo County, California, from the widespread subsp. thurberi. Subspecies gilmanii has flowers on the small side of those found among other populations of P. thurberi, although floral attributes do not readily distinguish between the two named subspecies. Davis and Thompson also noted another form that has relatively small leaves on and closely appressed to the inflorescence-bearing stems, although they did not formally distinguish this variant with a name. Morphometric and phylogeographic studies are warranted in P. thurberi to test whether morphological variation is significant, geographically partitioned, and associated with genetically isolated lineages.

(Discussion copyrighted by Flora of North America; reprinted with permission.)

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Parent taxa Loasaceae > Petalonyx Loasaceae > Petalonyx
Sibling taxa
P. linearis, P. parryi, P. thurberi
P. linearis, P. nitidus, P. parryi
Subordinate taxa
P. thurberi subsp. gilmanii, P. thurberi subsp. thurberi
1.Hairs on inflorescence-bearing stems ± retrorse.P. thurberi subsp. thurberi
1.Hairs on inflorescence-bearing stems ± erect.P. thurberi subsp. gilmanii
Name authority S. Watson: Amer. Naturalist 7: 300. (1873) A. Gray: Pl. Nov. Thurb., 319. (1854)
Source Flora of North America vol. 12, p. 544. Flora of North America vol. 12, p. 545.
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