Pylon crabs appear in Etrian Odyssey Untold as common enemies. They are hermit crabs whose shells resemble traffic cones from before the Apocalypse. They were most likely genetically engineered creatures.
There is another variant of these crabs, called Calamity Crabs, encountered as F.O.E.'s on the final floor of Gladsheim. They may not be dangerous, but they use stalling tactics against the player, wasting their time in stopping the activation of M.I.K.E.'s Gungnir unit.