The shell on their back was actually grown by the crab itself; only when they grow much larger, into a Daimyo Hermitaur, they will replace it with a Monoblos skull, or into a Diablos skull if they grow into the Plum Daimyo Hermitaur. Hermitaurs are the tropical version of the Ceanataur, a blue Carapaceon that lives in Volcanic regions.
They live mainly in Jungles and Deserts, usually near water, but can also be found in the cave systems of the Swamp. When they are left undisturbed, Hermitaurs are most often seen picking through sand with their claws, presumably searching for food. Sometimes, a Hermitaur may wait beneath the ground for prey or a hunter to pass, jumping out of ground and striking them when they walk over. A Hermitaur that's burrowed underground can be spotted by the puffs of dust that it regularly spits out. Hermitaurs have a nasty temper, and will attack just about anything.
Monster Hunter Freedom 2 / Monster Hunter Freedom Unite
A small Carapaceon with an incredibly hard shell. Known to live in great numbers in the desert, or lurking underground, one must be careful when treading in its domain. Its brains are said to be a true delicacy.