Carcinisation (American English: carcinization) is a form of convergent evolution in which non-crab crustaceans evolve a crab-like body plan. The term was introduced into evolutionary biology by L. A. Borradaile, who described it as "the many attempts of Nature to evolve a crab".
Definition of carcinised morphology
It was stated by Lancelot Alexander Borradaile in 1916 that:
... carcinisation … consists essentially in a reduction of the abdomen of a macrurous crustacean, together with a depression and broadening of its cephalothorax, so that the animal assumes the general body of a crab
Keiler et al., 2017 defines a carcinised morphology as follows:
"The carapace is flatter than it is broad and possesses lateral margins."
"The sternites are fused into a wide sternal plastron which possesses a distinct emargination on its posterior margin."
"The pleon is flattened and strongly bent, in dorsal view completely hiding the tergites of the fourth pleonal segment, and partially or completely covers the plastron...