Publication: Haseltonia 2: 39. 1994.
Notes
Disambiguation notes courteously provided by Mr. Dorde W. Woodruff, Salt Lake City, Utah, USA
The fact that Mr Siler of Southern Utah was the first to collect both Pediocactus sileri and Sclerocactus sileri, different species, in the 1800s, is a cause of some confusion…
…The only synonyms for Pediocactus sileri, apparently, are Utahia sileri and Echinocactus sileri. This cactus is quite distinctive, larger and coarser than some of the other Pediocacti. The dark spines and the wooly areoles are distinctive even on an herbarium sheet. And it only grows on that peculiar badlands clay soil, farther west than Sclerocactus sileri… …
Sclerocactus sileri is a different case, harder to distinguish when not blooming from the other small Sclerocacti, because it’s not so different-looking. That’s probably why it has had several other names. Being so isolated, it probably does deserve its own name… …Sclerocactus sileri grows to the east of Pediocactus sileri, in red sandy soil. It’s a smaller plant, and scattered, as the small species of Sclerocactus tend to be, though it has more locations than we knew of in the 60s, when I first found it…
…As noted in the online version of The Flora of North America, Ken Heil and Mark Porter claim that there is no support for this species being placed in either Sclerocactus pubispinus or Sclerocactus whipplei.