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I've trawled through Llifle for over an hour but can't come up with anything close to what I've got here. Could the second one be some sort of Eriosyce curvispina? It was labelled Matucana but pretty sure that's wrong. Both are in 2in pots.
Many thanks

Notocactus horstii?
Second one looks like Matucana calliantha (Matucana crahnii)

Thnks Lucy. Good spot on the Matucana. I don't know how I missed that in Llifle, blindingly obvious now that I look again. Not convinced about the other one, but maybe it needs to grow a little more. I was wondering if it might even be an Echinopsis.

I would guess Echinopsis or Trichocereus (if the spines are hard) for the first one.

mmcavall wrote: ↑Fri Jul 29, 2022 1:25 pm I would guess Echinopsis or Trichocereus (if the spines are hard) for the first one.

The spines are actually quite soft.
Going down the Notocactus/Parodia route I'm wondering whether it might be N. magnificus?

N.magnificus is indeed a possibility

Eriocactus magnificus
Matucana krahnii

Thanks for the confirmations, anttisepp.
Are Parodia, Notocactus and Eriocactus interchangeable? Which one should I go with?

gillinger wrote: ↑Sat Jul 30, 2022 7:58 am Are Parodia, Notocactus and Eriocactus interchangeable?

Yes and no. When labeling my plants I took a dive into Parodia/Notocactus taxonomy and it's messy. Your plant has been validly published under several names, including Eriocactus magnificus, Notocactus magnificus, and Parodia magnifica. Whatever name was more popular at the time it was published was the name people continue to keep. But as it turns out, DNA studies have shown that Eriocactus, Notocactus, and Parodia are genetically distinct enough to form their own groups (they form monophyletic clades), so in that sense you really shouldn't label an Eriocactus as Notocactus. But looking at these genera (Eriocactus, Notocactus, Parodia) in the broader context (as in comparing them with other cacti from diverse genera), it turns out they, along with Brasilicactus, Brasiliparodia, Wigginsia, and probably Bolivicactus (not sure here, but this seems to have been separated out of Parodia by Lodé), are genetically more related to each other than they are with all other cacti (all of them together form a genetically monophyletic clade). So if we want to classify these plants by how genetically close they are, Parodia is the oldest name, so everything else inherits it. Something I should mention, Brasilicactus and Eriocactus are not valid names, despite their common use and attempts to make them valid. The names Acanthocephala and Eriocephala, respectively, are older and more "correct".

Which one should I go with?

That's the fun part: go with what makes more sense to you. Ultimately, no one will punish you for using an unpopular name. Personally, I think we should phase out older names in favor of the names the current science supports. So in this case, either Parodia or Eriocactus (Eriocephala!) would be more "correct" than Notocactus, depending on whether you think it's more important to uphold a larger genus to show that the various subgenera are genetically related, or if you think it's more important that said subgenera are genetically distinct enough to warrant promoting their rank to genus level. As for me, right now I feel comfortable with lumping everything under Parodia, but who knows, I may switch that up in the future and use the smaller genus names.

Wow! That's some explanation! Thanks for taking the time. I agree that lumping everything under Parodia is simplest. I'll let others, more qualfied, sort it out and they can get back to me when they've made a decision.

As MrXeric says all the "Code" asks for is a name to be validly published then you can use it. The "Code" in only concerned with nomenclature (legal naming of plants) not classification. Classifications are optional, you can adopt or reject any you want.

When "Lumping" the oldest name takes priority. However as MrXeric says DNA has shown some of the "lumping" classifications like some of Hunt's are not monophyletic = all originating from the same ancestral line. Therefore need to be broken up again. For instance Hunt's Rebutia lumping.

If you desired a monophyletic classification you could "ultralump" all cacti in the same genus (though not many would follow you) using the oldest name available and it would still be monophyletic since they all arose from a common ancestor. But if you then decide on smaller genera, as the ev0lutionary lines have already started to diverge you cannot include species from the two already diverged lines (polyphyletic classification) as in the chart in the link if you want monophyletic classification.

https://www.mun.ca/biology/scarr/139417.jpg