At least in the United States, Echinocereus pectinatus (diploid) has only pink or purple flowers, unlike the polymorphic species E. dasyacanthus (tetraploid). Echinocereus pectinatus differs from the entire E. reichenbachii species group in that the areoles of its relatively thick-walled flower tube have stouter spines and much shorter hairs. Superficially similar species west of the Continental Divide, formerly associated with E. pectinatus (E. pseudopectinatus, E. rigidissimus, and some Sonoran species), are more closely related to the E. reichenbachii species group with densely bristly flower buds and delicate, ephemeral inner tepals. Echinocereus pectinatus var. pectinatus is endemic to Mexico; reports from the United States were misidentifications of var. wenigeri, E. pseudopectinatus (in Arizona), and unusually short-spined plants of E. dasyacanthus.