Thelocactus bicolor is native to southern Texas and northern Mexico, being found in Coahuila, Nuevo Leon, San Luis Potosi, and Zacatecas. Plants occur on limestone or sandstone slopes and outcrops from about 1300-7900 feet elevation. The plant has a single body with an ovoid shape, usually reaching about 6-8 inches tall and about 3-4 inches in diameter. The body is densely covered with colorful spines, having 3-4, yellowish or reddish central spines and 8-18, yellowish or reddish radial spines. Large magenta flowers are 2-4 inches across.