Since @Baja_Costero just uploaded a photo, i spotted this...
Those arent ferocactus spines...
Denmoza perhaps?

@mcvansoest do you know what the plant in the picture might be?

Looks like a pretty old Ferocactus to me. When it was younger it was grown under brighter light conditions hence the more fierce spines at the base, then it must have gotten in some shade and the spines have gotten thinner.

Do I think it is Ferocactus chrysacanthus? From that picture certainly not, but on old Ferocacti spines often go black and become messy. We'd need to see the young growth to be able to tell if it is F. chrysacanthus.

As to it being a Denmoza? I do not think so, the spinage looks pretty typical for what you see on old fairly tall Ferocacti, but some of the older taller Denmozas may look similar, though most (but not all) pictures I have seen of old tall Denmozas show a much more 'hairy/furry' looking plant.
The Denmoza I have in my front yard is not that tall, but is already starting to get a more furry look with the radial spines becoming pretty prominent.
I would say that while there are definitely some similarities between some of the older Denmozas and older Ferocacti, one thing that I think sets them apart is how generally the radial spines are carried. To me on the plant in the picture being questioned in its older more fiercely spined area the radial spines strongly suggest Ferocactus to me.

So my sense here is that it is an actual Ferocactus, but I would doubt its positive ID as F. chrysacanthus, despite its sign. What intrigues me about the sign is that someone appears to have crossed out the name... If I had to suggest another ID aside from another Ferocactus, I'd say it is F. cylindraceus

Could it be eriosyce? Those are one of the few cacti that make hooked spines, and the upper spination is also a match....
Or some kind of echinopsis? Something among the lines of leuchatha, one close relative of it....?
Ive not seen a photo of an old ferocactus with such drastic change in spination...
It clearly had hooks when younger, but when it reached a certain age, not so much.....
Cacti are weird.....

Thijs, you're very observant and I think you're right that the plant is a Ferocactus. It does appear the name on the tag was seemingly crossed out by somebody, and the radial spines are informative. For what it's worth, I would not be comfortable identifying the plant without seeing some younger spines near the growth point. I see no compelling reason to move it at this time.

F. chrysacanthus is supposed to get relatively big (over 3 feet tall and 1 foot wide) though I have never seen a plant anywhere near that size. It may also make 6-12 radial spines which tend to be insubstantial but in some cases may be "needle-like" according to my cactus book by Anderson. So those things check out.

Interestingly the location is given as 98108, which is a postal code near Seattle, Washington... maybe it's in a greenhouse there? The member who posted the photo has not posted anything for a year or so, but hopefully will check in at some time to help sort this mystery out.

Could it be a really masive echinocereus ferreiranus lindsayi?

Stefan, of the plants you mention as possible alternatives only the Denmoza gets anywhere close to the size that that plant in the picture already is.

That plant is at least 20 cm wide so probably at least 60 cm tall, but probably more...

I will re-iterate that it looks like this plant when younger was grown in bright light - full sun conditions and now it looks like it is in a green house, or at least in conditions with more shade. When shade grown most cacti used to harsh full sun or very bright light conditions tend to make spines that are much thinner, smaller, and fewer in number.

I have no pictures of it, but I have a golden barrel cactus that I put in a pot to give to someone, but who ended up really liking another cactus so I gave her the other cactus instead. The GB got stashed in a pretty shady spot, for a bunch of months - during its growth period - and went from its typical fiercely spined look to something with very wimpy spines. I moved it into more sun and it started producing normal looking spines.

But we are not talking about wimpy spines here....
I can see size and lenght variation and colour change at my barrel cacti during summer and winter....but this goes beyond that...
Bottom line is, if it were any ferocactus ive seen, it still maintain those hooks and hard spines, only they would be shorter, less formed and discolored...
Looking at the picture over and over, i cant see something resembling a ferocactus areole with a thick central spine, its simply as wimpy looking as the rest...which shouldnt even be shaped or arranged like that in the first place
As for the color, its also strange... I dont know a lot of barrels with black spines.....most of them are way different thant this...
Only one i did find to remotely match this is ferocactus lindsayi and i cant find a picture of a really old one....

Regarding the putative younger days in full sun and the differences in how the spines look... I agree with that analysis. It kinda looks like the plant was collected from habitat or from somewhere it was growing outside in the ground. The central spines really stand out down there in the bottom part where the areoles are packed tighter together and most of the green color has been lost. And then starting almost halfway up in the photo it's showing signs of a more pampered life (its present existence, from the looks of things).

This is a typical appearance that I recognize from Ferocacti around here which were harvested from habitat (illegally or as part of a rescue operation) once they have spent some time in a greenhouse, or just getting regular water and fresh soil. The wild parts are gnarly and extra spiny and thrashed, the parts that came later in cultivation are all regular and evenly spaced and subdued-looking as far as the spines go.

I've seen Ferocactus cylindraceus in the wild in Washington County, Utah and the lowermost spines are black due to age and because they are slowly decomposing. The spines will even fall off eventually and they'll even startle you if you don't look closely because they resemble huge black spiders.

...but the younger spines are black...
Baja im familiar with light and habitat change....
Ive seen photos of 2 same plants grown in full sun and in shade cloth...
if youve guessed, full sun had much more ferocious spination..
but thats not what im saying....
The upper parts are simply not ferocactus to me.....

But it is.

What device are you using to view the forum(and the photo to that extent)?

This a photo of the ferocactus with the winter/summer spine variation...
My oldest living cactus btw....

That is a good looking plant.

I have a ~26" iMac with HD display. It is not that I cannot see the image properly, I am just completely convinced, the more I look at the lower level of the spines on that plant, that it is a Ferocactus. I have already stated I do not think it is F. chrysacanthus, but unless we can see young new growth the picture in question does not allow us to determine that with certainty.

The poster, if he responds, will likely argue that the label states it is F. chrysacanthus and that is why he posted it here in the database. I cannot fault him for that, despite my doubt about the proper ID, and the fact that even at the best Botanical Garden institutions mistakes get made or the occasional mis-identified plant gets added to the collection. However until we have evidence that without a doubt shows it is not F. chrysacanthus this photo either stays here or at most gets moved to the Ferocactus sp. entry. I would be fine with that as I do doubt the ID, but not that it is a Ferocactus.

And am I sorry, because I hate to be the guy who has to say that your personal observations and conditions do not count, but unfortunately in this case your summer/winter variation example is nothing like taking a plant grown for most of its early life, possibly as long as 15-20 years in say a southern California desert nursery or actually on Cedros island and then moving it to a green house environment somewhere else completely, implying that the conditions outside would not be suitable for the survival of that plant. So it goes into a possibly much cooler, likely more humid and less sunny environment on top of the fact that it is in a green house where a lot of any remaining harshness of the sun is blocked out. I do know how long the plant spent in that environment but given its size probably at least another 10-15 years if not more.

In these kind of conditions spine development will not favor the characteristic thick flat central spines we are so used to seeing on Ferocacti and radial spines may be minimally or not at all present, giving the cactus a very different look. However, absent an obvious graft, this plant did not go from being a Ferocactus in its early years to something completely different later, the conditions just affected its spine growth and it did not just experience a season of major change in conditions it experienced many years of it after having had very different conditions for many years before that. Most cacti take a good chunk of time to get past an experience like that and in some cases they never do, looking like a diminished version of themselves for the rest of their lives or until they get better conditions.

Something comparable but the opposite and much more extreme would be you sending me that Ferocactus you posted a picture of and me putting it out in the full sun in the summer in my front yard. It would be shocked so baldly it would probably be dead in a couple of weeks, but if it did survive in a few years there is a pretty good chance you would have a hard time recognizing it.