Well, this is not so simple as wikipedia says. Crustaceans are a really big and wide group of life forms, and Carcinisation can be applied only to some groups of decapods (about 15.000 extant species). There are also about 11.500 species of Copepoda, 10.000 Isopoda, 13.000 Ostracoda, 9.500 Amphipoda and 1.300 Thecostraca, for instance, and none of these are crabs.