Creature from a dream I had last night.
Mosasaurus-(or other aquatic reptile)like body, purple-ish gray with darker stripes, dimetrodon-like head but more "fish-y".
It looked pretty close to this as far as I can remember.
It wasn't less creepy in the dream as it looks here. It was somehow pretty intelligent and could speak to me. Said something mysterious and creepy to me once (can't recall at all what) and stayed quiet after that.

In the dream it lived in a big fish tank that was owned by a big circus.