Hunt refers this taxon to synonymy with M.nana; to my way of thinking it has more to do with M.crinita.
The Fitz Maurices are of the opinion that it falls within the concept of M.crinita, which in their opinion embraces M.nana also.
Mammillaria - John Pilbeam pag.325
Mammillaria felipensis REP 636
REP 636 - San Felipe, 2200m - Guanajuato - Mexico