Pringles

[Brontosaurus]

Mammillaria pringlei
Mammillaria rhodantha ssp. pringlei

Can anyone tell me:

a: Are these two different cacti or two different names for the same cactus?
b: If they are different names for the same cactus, is there a consensus on which one is correct?
c: What name is preferred?

[greenknight]

Same cactus. The red-spined Rhodantha and yellow-spined Pringlei were formerly considered separate species, but were merged years ago since they're basically identical except for the spines. Both are valid names, but Mammillaria rhodantha ssp. pringlei is generally preferred.

[Brontosaurus]

Thanks!