Obregonia denegrii is the only representative of its monospecific genus and is related to Ariocarрus. The stem is solitary, globular-squashed, resembling an inverted pine cone with a woolly center. It is grayish-green to dark green and up to 6 inches (15 st) in diameter. Flowers grow between the arech's wool, in the center of the stem on young tubercles. They are white, diurnal, funnel-shaped, and up to 1 inch (2.5 cm) in diameter. Fleshy edible fruits are white, pear-shaped, and hidden in the wool.