mazatlanensis, sheldonii or something else?

Both of these plants came as M. mazatlanensis but just look so different that I'm doubting the ID of atleast one of them and possibly both.

First plant as it flowered last summer. Black hooked spines and thin stems.


Second plant that I just aquired. Red hooked spines, stouter body and lots larger flowers.

Hi Snowfella, I would be ok with calling them both M. mazatlanensis. This is a species that has a wide distribution and can vary a lot.
Your no.2 plant leans towards the recognised discription of 12 to 18 white radial spines, with 1 to 4 reddish brown central spines , with one hooked. Also has large wide flowers,ranging from pink thru to carmine. No. 1 could be M. mazatlanensis ssp. patonii, which has appeared in recent years and is reported to have greyer radial spines with possible brown tips. Central spines tend to be blackish brown, later turning to ash brown. Flowers are also smaller. It is said to originate from the Islas Marias in the Gulf of California, off the coast of Nayarit. Hope this helps.

Del is right, M. mazatlanensis has quite a wide distribution and as a result a lot of other names and varieties have been erected.

These two plants illustrate very clearly why I prefer to obtain plants which have some sort of field collection data, although to some extent it spoils the fun of trying to name plants correctly, but does avoid the ignomony of getting it wrong!

If you look at the descriptions of M. sheldonii and M. mazatlanensis, and go just by spines count, then both the plants could be either species. There is a difference in central spie colour, that I have found that to some extent depends on UV levels.

The flower colour can separate them usually, M sheldonii being more pink, and M. mazatlanensis rather darker, as can the fruit colour - brown-reddish yellow in the case of M. mazatlanensis, red for M. sheldonii, and the seed colour also - brown for mazatlanensis, black for sheldonii.

Thanks.
Guess to add to my confusion about these 2 is that the nursery changed their labeling on these plants last summer, they all had sheldonii labels but all of a sudden swapped to mazatlanensis on all 3 varieties. 3rd one being a straight spined form with reddish centrals.

I wonder what made them suddenly do that?
Both sheldonii and mazatlanensis have straight spined forms, so that's no help.
The flower of your second plant does look more like a mazatlanensis flower to me. Not sure about the first though..

Better late than never here. Not really sure why they all of a sudden changed, their labeling leaves lots to be desired to begin with so one thought that has crossed my mind is that they plain ran out of M. sheldonii labels

One of my straight spined ones finally flowered today in a newly constructed outdoors bed, guess it's getting the shock of it's life with full sun and 40+ degree temperatures all of a sudden.


It's been slowly adapted to full sun though through the use of sunscreen for a few weeks before I planted it in on friday this week, just in time for a heatwave to hit

It sounds like you have had some very hot weather in Australia recently, so I can well understand the need for acclimatisation. That is a nice plant, and I hope the sun encourages it to continue to flower.
From the flower, I would tend towards M. sheldonii rather than M. mazatlanensis, based upon the paler flower and the more prominent mid-stripe. But it might be that the sun has bleached it somewhat, although the plant looks more mazatlanensis in nature to me than sheldonii.
Maybe Jonas Luthy was right in his consolidation of sheldonii and swinglei under mazatlanensis, and suggested that they are in fact just one variable species, just changing a bit as the distribution progresses down the coast from Sonoroa to Sinaloa to Nayarit.
Or maybe not
I am firmly sitting on the fence....as you can no doubt sense.

I'm not to concerned with it keeping on flowering, more with it surviving the heatwave having just been planted out! Well over 40C in the air today and I recorded surface temps on the soil in that bed of near 65C the other day. Expected to stay over 30C untill well after midnight tonight.
Even with the plants having been introduced to the sun gradually I'm still seeing sunburn so have had to erect some temporary, and not so pretty, shade structures for the more tender ones.
Funny enough the Mamm's show not a hint of burning and it's instead Noto's, Echinopsis and even Opuntia's that are turning yellow

Here's the partially finished cacti bed that last plant now reside in, there's a handful of Mammillaria's in there. Topdressing still remains to be added.


Got a second smaller cacti bed with among others M. mystax and M. compressa that have been going nuts with growth since I put them in. Mystax went from never having flowered for me to putting out litterally hundreds of flowers through early spring.