Carcinization in the Anomura – fact or fiction? I. Evidence from adult morphology

Carcinization, or the process of becoming a crab, has been, and continues to be, a focal point of anomuran evolutionary hypotheses. Traditional examples of carcinization in the Anomura are most celebrated among hermit crabs but certainly are not limited to this group. Carcinization, if it has occurred, has done so independently in all major anomuran taxa. In this critique, the traditional examples of carcinization in the Anomura are reviewed and more modern variations on the theme assessed. Potential pathways of carcinization are examined from perspectives of adult morphology in the Paguroidea, Galatheoidea, Hippoidea and Lomoidea, with emphasis on the Paguroidea. Specific attention is given to the theoretical transformation of a hermit crab-like body form into a “king crab”- like lithodid crab. Resulting coercive evidence indicates: (1) that while the evolution of a crab-like body form certainly occurs, the traditional applications, based on inadequate and often inaccurate data, are flawed; and (2) that lithodid crabs did not arise from a hermit crab predecessor through the process of carcinization.