With its long gray tubercles, this is probably the second largest growing species in the genus Ariocarpus. In habitat the individual heads reaching a diameter of about 8 inches rarely more and forming large clumps to about 18 inches across. Another one with a confusing taxonomic history with names changing rank from species to subspecies or even variety. Some consider there to be A. retusus subsp. confusus, A. retusus subsp. trigonus, A. retusus subsp. retusus, and A. retusus subsp. retusus var. furfuraceus. We tend to leave A. trigonus as a distinct species.