I agree, Wiebe, it does look more like M. thornberi., but probably not yaquensis, whose spnes usually are darker, and stems slimmer. DAR167 comes from nr. Lukeville, Organ Pipe Cactus Natl. Mon., Pima Co, AZ. You can find M. microcarpa (grahami), M. tetrancistra and M. thornberi in that area. If the plants are not in flower, it can be quite difficult to identify habitat plants.
Amante Darmanin doesn't list M. thornberi, and DAR167 was the only Mamm that he collected in this area, the others being Ferocacti. He had collected DAR162, as M. microcarpa in Sonoyita, Sonora.
I suspect that this plant is M. thornberi, and that the identification is wrong. I doubt cross fertilisation is the case here, much less likely.