The spikes on the back of the Stygimoloch are actually resorbing, which means they're getting smaller as that dome is getting bigger.

For thus says Yahweh to the men of Judah and to Jerusalem, Break up your fallow ground, and don't sow among thorns.

For thus saith the LORD to the men of Judah and Jerusalem, Break up your fallow ground, and sow not among thorns.

Evidently, a piece this big of tentacle has a hundred thousand little barbs on it and each barb is not just stinging your skin, it's sending a venom.