Mammillaria thornberi v yacuensis native ti west of Sonora state. It forms loose clumps of pencil thin stems, dark brown in color if grows on full sun. It is easy in cultivation but not very common plant, with peculiar look and nice flowers.
The flowers with long stigma lobes a very characteristic to the group of western Mammillarias. Genetic studies has shown that this group has somewhat remote relation to other plants in the genus and may some time later be taxonomically separated from it