This is a public service announcement, this fucker is a cross between a Wharf Roach (giant isopod edition) and a Trilobite.

The Japanese name has a suffix that is exclusively used for isopods.

Before any horseshoe crab and silverfish lovers try to shove they're beloved horseshoe crab/ silverfish into this equation, the entire creature can be explained exclusively with a Giant Wharf Roach and a Trilobite. Occam's razor away the fluff.