Yes, they are on extinction. In the desert dome, they take the form of rubble golems. They are extremely common as a guard for the desert titan terminal. Rubble golems have less health though so they can easily be taken out by a good velonsaur or managarmr. They give the same loot as the big one though, so get farming.
If you are unsure if a rock is a disguised golem or not, a spyglass shows their name and level even when disguised. Also, when disguised, the rocks often move slightly as you get close, re settling onto the terrain.