King Crab

http://commons.wikimedia.org/wiki/File:Bathynomus_giganteus.jpg
Image: Wikimedia Commons

All right, keep your seats. Bathynomus giganteus is an example of “deep-sea gigantism,” where creatures assume huge sizes in the cold black mud a mile down, perhaps to better regulate body temperature.

It’s related to the woodlouse, if that’s any comfort.