http://swbiodiversity.org/seinet/taxa/index.php?taxon=15520
http://plantsoftheworldonline.org/taxon/urn:lsid:ipni.org:names:134810-1
http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=242415367

FNA: "Mammillaria meiacantha is regionally sympatric with both varieties of M. heyderi, without resulting in hybridization. West of the Rio Grande, reports of M. meiacantha probably are misidentifications of M. heyderi var. bullingtoniana. Mammillaria meiacantha has not been documented for Arizona."