The clue is in the name of the order to which crabs belong: decapoda. The decapods also include crayfish, lobsters, prawns and shrimp(s). In many species (as for example the crabs), the legs of the front pair are enlarged and have pincers.
According to Wikipedia, "Decapods can have as many as 38 appendages, arranged in one pair per body segment ... ten of these appendages are considered legs ..., found on the last five thoracic segments ... In front of [these] are three pairs which function as feeding appendages. The head has five pairs of appendages, including mouthparts, antennae, and antennules. There are five more pairs of appendages on the abdomen [and] one final pair [which] form the tail fan."
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