Engelmann & J. M. Bigelow, Proceedings of the American Academy of Arts and Sciences 3: 293, 1856 
Herbarium; Herbarium; Herbarium; Herbarium; Herbarium; Herbarium (submitted as O. aff polyacantha); Herbarium (submitted as O. polyacantha); Herbarium (submitted as O. polyacantha); Herbarium (submitted as O. polyacantha); Drawing (Britton and Rose, v1 1919, plate XV)
Opuntia tortispina is a prickly pear cactus that has been confused with O. cymochila, O. mackensenii, O. phaeacantha and other opuntias. O. tortispina may grow alongside the other prickly pears, but it is distinct. O. tortispina is often spinier appearing than other nearby species of Opuntia and is a low, creeping, spreading, and sprawling plant (Powell and Weedin). It seldom exceeds 30 cm tall. The pads are obovate or long obovate about 10-20 cm long and 7-12 cm wide. Areoles over 2/3 of the pads have spines, often 3 to 5 centrals (typically white or tan). Areoles are closer together on O. tortispina than on O. phaeacantha. Pads may/may not have transverse wrinkles in winter; however, unlike O. cymochila the wrinkles smooth out when turgidity returns. Flowers may be all yellow or may have reddish centers in this prickly pear. The fruits are juicy and obovate to elliptic (Weedin and Powell). See a table comparing O. tortispina with O. cymochila. See the original description. O. tortispina is hexaploid or tetraploid. The two different ploidy levels that have been reported for this Opuntia may mean that two different taxa exist.
This Opuntia is found in sandy soils in mid-altitude woodlands and grasslands and irregularly in other locations. O. tortispina is found from northern Mexico to CO and AZ to TX. Some botanists consider that O. tortispina is a species of hybrid origin (O. polyacantha and O. macrorhiza). However, such hybridization would have occurred long ago. It is a stable, self-reproducing stand-alone species now.