CactiGuide.com

Here are three photos of a cactus that I think is a Parodia. I have had it 18 months. It has more than doubled in height to 5 inches(12.5cm), and is now wider at the top than below. It has not blossomed. It has small tubercles between the arioles.

Looks more like P. mammulosa than anything else, I'd say. That is a highly variable taxon, also could be crossed with another Parodia.

Appears it was a bit etiolated, but it's now in better light. It's not bad, though - it's just become columnar at an earlier age than it would have.

Is P. submammulosa a valid name?

This plant is unusually elongated, maybe lack of direct sun? Much better to come back with flowers.
Seems to me it's not clear Notocactus mammulosus but also would be useful to close floricomus, roseoluteus, schlosseri?

Thank you all. I was anticipating you experienced growers to say P mammulosa or mammulosa hybrid, and that seems to me most likely. In response to anttisepp, I have what I believe is a P erubescens (N schlosseri) (see below) but it is quite different and has no tubercles.

The shape is little unusual but spines match Notocactus mammulosus. Some variants with age can look like this too.
https://notocactus.eu/notoblog/entry/no ... aulus.html#

Looking at Llifle's synonymy under Notocactus mammulosus (You need to click on "see all synonyms") the combination for P. submammulosus does not seem to have ever been made under Parodia if his synonymy is correct?

http://www.llifle.com/Encyclopedia/CACT ... mammulosus

Hofacker made the combination Parodia mammulosa ssp. submammulosa and Keisling Parodia submammulosa ssps. minor. Possibly the first may be valid but not sure if the second is if there was no valid publication under Parodia for P. submammulosus at the rank of species? Probably a tame botanist could tell us if one is available?

Certainly the name is valid if you want to call it Notocactus. To be valid a name simply has to be validly published under the "Rules". This has nothing to do with classification as such since classifications come and go. Meaning the latest classification is not obligatory if you disagree with it and want to say keep Notocactus separate from Parodia.

Your plant is certainly a Notocactus or that group in Parodia and probably is something in Llifle's list of synonyms for P. mammulosa. Though not a "splitter" I often prefer to retain some of the older smaller genera as an aid to classification, whereas the "lumpers" tend to use sections within a genus to try and congregate similar species together. The choice is yours since no classification is mandatory and only the classifiers opinions.