Unknown Mammillaria 3

Tagged as M. compressa, but I find it very different to two other M. compressa I have taken photos in the past.

Regards,

It reminds me of polythele durispina but the flowers aren’t pink........hmmmmm

I see what you mean. Let's wait another suggestions then. Thank you.

Not compressa, I'd suggest M. winterae ssp. aramberri

In another cacti forum I've been suggested it could be M. magnimamma. What's the difference with M. winterae ssp. aramberri? I find them very similar.

Yes, magnimamma is a possibility. While magnimamma does offset, winterae aramberri offsets with individual heads about the same size. Magnimaam tends ot have one main head and then smaller heads, and grows rather flatter.
The difference isn't immediately obvious, but when you know where these plants originate from, and who they are related to, it is clear. Why not check out the descriptions on mammillarias.net and see what you think?

Ok. I've checked out the descriptions of both species, but I find it hard to make up my mind. By the way in the description of magnimamma it says: "Radial spine: 2 – 5, sometimes more, extremely variable, unequal, awl shaped, whitish to yellowish, with dark tips, 15 – 45 mm (0.6 – 1.8 in) long, lower one curving downwards; Central spine: Usually absent.", while in the description of winterae ssp. aramberri it says: "Radial spine: Absent.; Central spine: 4 – 6, needle-like, brownish with darker tips, usually 4 radially placed, with the two extra spines when present more central, and slightly longer.".
I suppose this to be an error because I see spines in both species very similar, although I'm not sure of the difference between central and radial spines in this case.

Edit: In the descriptions the size of the stems are very different too. 20 – 30 cm (7.9 – 12 in) in diameter for winterae and 10 – 12 cm (3.9 – 4.7 in) in diameter for magnimamma. If this is correct mine has to be magnimamma, but 20-30 cm? Isn't it too much?

My first impression was that it looks a lot like M. crassimammillis, which Hunt decided to transform into M. winterae subsp. aramberri. In my opinion, M. crassimammillis / winterae subsp. aramberri has nothing to do with M. winterae, except for the flower colour, which is a bit like the flower colour of M. winterae (but, roughly spoken, that was more or less the philosophy of Hunt: they look similar, they must be the same species).
But the fairly long, curved spines don't really fit for M. crassimammillis. So, I don't know what it is, but M. magnimamma might then be the most likely option.

You are mixing up some descriptions: The 20 -30 cm is for M. winterae, not for M. crassimammillis. M. winterae becomes really big, 20 -30 cm in diameter and usually stays single. But M. crassimammillis has rather small heads (about 5 cm in diameter) and offsets strongly. It forms big, rather flat clusters in nature. I once tried to pull an offset from a big cluster in nature, but that was really impossible without enormously injuring the plant. And because I also did not find fruits on these crassimammillis, I only took photos fro mthese plants.

Wolter ten Hoeve.

Thank you Wolter for the information. Respect to description of M. winterae ssp. aramberri, I borrowed it from mammillarias.net, where they don't make any distinction between the size of that subspecies and that of M. winterae ssp. winterae.