I bought this unidentified cactus yesterday and would like to know what it is. It's about 4 inches in diameter. My best guess is a Gymnocalycium species (Chin cactus). If that's so I haven't been able to narrow it down to a particular species. Any thoughts?

Btw I am new to the site but hopefully I've posted this in the right place. And thanks in advance.

Yes. To me(at first glance) its monvilei

Yes, this is exactly the right place to ask about cactus. Yes, Gymnocalycium but I wouldn't be so quick to assign a species. Maybe when it blooms, we can add a more definite ID.

Thanks very much for the replies.

Gymnocalycium monvillei is a very good match. Hopefully it will flower next year. It is in a sunny east facing window.

There are several Gymnos that would be a good match. And, depending upon where you live and where you got the cactus, it would be more likely for you to find some Gymnos more easily than others. Don't jump to conclusions.

My first question would have been to Skopjecollection, asking why he thought that. Skopje lives in Europe so his commonly found plants may not necessarily be your commonly found plants.

Gymno monvilei is somewhat common, even here. Bear in mind, when it comes to availability, i operate on hard mode
cacti guide also says "common"
https://www.cactiguide.com/cac...
I used to own one(mistaking for a ferocactus). Thus i am familiar with spines and shape.
Now...i only own its slightly rare variety, horridispinum.I nearly bought a regular one, but it was mislabeled as echinocactus grusonii , and slightly more expensive...
Considering how most cactus wholesale is fairly similar, its a safe assumption that it is this one, and not another gymnocalycium..

As for rarity,
-echinocereus triglochidatus
-cylindropuntia bigelovii
-echinocactus texensis
-graptopetalum bellum
-(ex) hoodiia
-(ex) huernia
-lophophora
-e.pachanoi
-euphorbia ferox
-opuntia fragilis
are the ones im certain i will not find in wholesale.
Ive looked at dutch "assortment" catalogues in all the bigshot companies, and ive seen none of these. In fact, i got real lucky these last 2 years. Ive certainly not even seen lithops here till june...

Echinocactus texensis is native here and the most abundant of the barrels. I give it away occasionally if someone wants to dig it out. It grows in tight soil and has a long taproot. Unless we've had recent rain it's hard to extract without a lot of damage. Too bad you can't get it. Reasonably cold hardy plant.

Like i said, certain plants have been gradually phased out of production in wholesale. You can immediately guess why the pachanoi and lophophora...
But the others? Only in specialist nurseries, or if really lucky...
This is what "used to be".
Mind you, nowadays, remove the fancy genera , and the unusual euphorbias, multiply by 0.7 and you pretty much get what i used to have and still have...