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Arms are strong, stronger than jaws. People can break each others arms just by playing. Grip strength can easily reach a point of crushing 75 kilograms and holding a pressure of 189 kilograms on average and some can reach a pressure of 605 kilograms at peaked strength.
I want a creature who's design is to have at least a mouth in one hand, where's fingers have strong claws to rip and tear meat and skin.
Apparently human hands are already strong enough to rip flesh or puncture skin but our fingers are covered in soft skin so it's hard ripping someone's skin without our own finger bones piercing our own skin. It's like punching a wall, even if the muscles are strong enough to apply the force needed to penetrate the wall, flesh is less dense than conctete, so the hand will break. This is why boxers can not pierce humans with their fists even if the force they can apply with a single punch is far greater than what human flesh can bear.
The human body can withstand 50 psi (pounds per square inch) and that's if it's a sudden impact. However if it's sustained pressure, the body can withstand up to 400 psi if the weight is gradually increased Science.ca
This led me to think about a creature with claws instead of nails, covered in enamel to make them as strong as teeth. And a lamprey mouth in the middle of the palm. It would work by ripping flesh off victims with claw strikes and then forcing the flesh into the lamprey mouth as it if was a meat grinder.
I want to know the validity of such a system considering the creature has two lamprey like mouths and a normal one. I guess there's a reason it never evolved, but maybe it could be possible with different conditions or evolutionary paths.