User blog comment:Jamintheinfinite/Subnautica Creature Evolution/@comment-28450065-20180331231031

I believe the Lava Lizard to be a closer relative of other animals rather than the Sea Dragon. The similar skin texture and ability to scoop up molten lava may be down to convergent evolution rather than relation.

The skin texture certainly has benefits against lava. And the massive size disparity between the two makes it seem unlikely. The Lava Lizard's forearms may also be down to convergent evolution since the ability to manipulate terrain is certainly helpful in a restrictive environment.

What it could be a relative of though, I don't know. The teeth are the same as Stalker teeth so it could be a very old species like the Stalker that diverged some time ago. The fin positioning on the Stalker and Lava Lizard is also similar and they both lack luminescence.