Mammillaria Species, Longmamma Nipple Cactus, Pale Mammillaria

I'm no expert but was reading up on this plant and from what I've gleaned, Mammillaria sphaerica is a subspecies of Mammillaria longimamm...Read Morea (vs a synonym as shown here on DG). (?) The photos I've seen show distinct differences; M. sphaerica seems to have much more bristly, webbed-like, semi-obscuring spines while the M. longimamma appear to have more prominent tubercles, less obscured by spines. The flowers look slightly different as well; M. sphaerica show some blushing on the outer tepals and darker orangish stamens, vs M. longimamma which are completely yellow. I see both represented in the photos here and was surprised/curious they were not distinguished separately as it seems easy to spot the differences. But then again as I said, I don't have personal experience, I'm just investigating currently. (I only post this because I find the images of what I take to be the distinct species, M. sphaerica, more attractive and am considering adding that one to my collection (vs M. longimamma)).

Heads flattened-globose to 5 cm across,clumping.Flowers 6 cm across.
Other name,
Dolichothele sphaerica

The fruit are reported to have a pleasant aroma.
The flowers are brilliant lemon yellow

Small knobby light green clumper from south Texas and n Mexico