What is this Euphorbia succulent?

Question

I bought this plant a while ago. The shop assistant wasn’t sure what it was, there was only one left, and all I got is that it’s a succulent.

It’s not doing great, and I hope knowing what it is could help with research.

The small leaves you can see at the top are square-ish, and there are always two new leaves growing from each of them, together with a wilted little thing that looks like it could be a flower - although I don't think I've ever seen it look very flower-y.

Since taking this photo late last year, the plant has not been doing well, and lost most of the top branches with the square leaves. It has recently grown a whole bunch of new big leaves, though, like the ones growing from the stem.

Does anybody know what it is?

Update: The first answer to this question suggests that it's a Euphorbia succulent, so that should narrow it down a bunch - but trawling the internet and clicking through page after page of images hasn't resulted in a match yet.

Answer 1

I'm not at all sure what this is, but I'm betting it's a plant from the weird and wonderful world of succulent Euphorbias. The thorny stem suggests Euphorbia milii which produces red or pink or white bracts; the closest I can find is Euphorbia milii grandiflora 'Green Apple' https://www.uhlig-kakteen.de/en/euphorbia-grandiflora-thai-hybr-green-apple.html but it isn't that either because the bracts are the wrong shape. There's a huge range of succulent euphorbias which look nothing like each other, but all produce a white latex sap which can be highly irritant on skin; this link https://www.succulents.us/euphorbia.html demonstrates quite how broad a range of succulent euphorbias there are (unfortunately, yours is not shown).

If you're prepared to, either break off a small piece of stem (wearing gloves) or push a pin into one stem or one of the larger leaves to see if the sap produced is white, which would at least confirm or deny that it is a Euphorbia.

If it is a Euphorbia, the likelihood is the top parts are actually bracts (what passes for flowers) and the production of new leaves is a good sign that the plant is healthy.

Answer 2

Since reading Bamboo's answer, I spent an ungodly amount of time clicking through literally thousands of images, and finally found the answer.

This specific succulent is called Euphorbia monadenium echinulatum, is at home in Zambia & Tanzania and was originally described in 1900 by a German-sounding guy called Otto Stapf.

There's more proof here and here.