Ahh, I see the magmasaur's picture's structure now. It's hidden pretty well but is definitely not natural.
It's worth noting that the structure with the magmasaur looks more tekky than the lunatic structure we see under the astroceti, although it's a bit hard to tell given how far in the background it is. It's certainly very big though.
Also, here's a closer-up less blurry picture of both of the structures.