Pediocactus knowltonii
 Pediocactus knowltonii is a rare species of cactus known by the common names Knowlton's miniature cactus Knowlton's pincushion cactus and Knowlton's minute cactus. It is endemic to San Juan County New Mexico in the United States. It is the smallest and rarest species in genus Pediocactus. It is threatened by a number of human activities. It is federally listed as an endangered species of the United States.This tiny cactus may reach a maximum size of 55 millimeters tall by 30 mm wide.