Heterotheca marginata Semple is a rare species found in Upper Sonoran desert in the Superstition Mts. and Pinal Mts. of southern Arizona.
Figure 32. Morphology and distribution of Heterotheca marginata. A. Habit. B-C. Lower stem leaf and upper stem leaf, respectively, adaxial surface. D. Head with only some florets drawn. E. Mid series phyllary with chlorophyllous zone dark; upper margins usually anthocyanotic. F. Mature achene with disc corolla attached. G. Distribution in southern Arizona based on all collections seen.