GIANT ENEMY CRAB!!! Historically Accurate?

And just in time for thanksgiving. Remember all that 'historically accurate' Japan fiasco at Sony's E3 press conference last year? Yeah, we all had a good chuckle at that. Turns out that there have been been actual giant [enemy] crabs in the past. (albeit much older than feudal Japan mind you)

"The size of the beast suggests that spiders, insects, crabs and similar creatures were much larger in the past than previously thought, the team says."

And, assuming you could knock one over on its back, I'm sure you'd be able to attack it's weak point for massive damage. Sony, sorry for doubting you.