Spineskates are basically Allora's Spiky Fish, albeit resized and with an extra spine added on either side.
Much like your idea, however flattened and with three spikes one each side instead of two. I imagine them being built like a skate, so their heads are simply rounded with the body rather than separated by a neck.
They have twelve tiny legs on their underbelly, allowing them to hide themselves in the sand.
Attack (bite): -10
They hide in the sand, leaping up only when prey has been detected in a surprise attack. They are relentless in chasing prey, however not terribly fast. They are the natural predator of the Monoculus.