Four Mammillaria are there the same?

Hello. In this photography, there are four Mammillarias, apparently same, but if we observe well, they differ in the central thorns and in the radial ones also. Could you help me?, Which are their names? Thank you

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Hi Joma
the three in the red pots look to me to be Mammillaria backebergiana, the one on the right I need some more time to ponder. I would like to hear from some other member to confirm my thoughts on the first three, as i,am not experienced enough, and do not have the confidence to say that this is this plant, i know from experience that there can be a lot of variation in these plants.

Thak you Arthur for your answer. The following pictures present a detail of the thorns of the four mammillarias. Beginning with the first of the left


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I think you are right, Arthur, with M. backebergiana. The central spines vary a lot in this species, according to the description, from 1 to 3, light brown to dark brown. I have a plant in my collection that has no central spine, or rather the one that might be a central is pale like the other radial spines, and pointing upwards almost in the same plane as the radials.

Without doubt, they are plants from the Polyacanthae series, and the Spinosissima group, which includes backebergiana, matudae, spinosissima itself and its variants, and meyranii. I favour them all being backebergiana.

Arthur, Criss. I have read your comments and observed the Mammillaria again and I accept your suggestions. Thank you for your help. joma