Stevci6, Zdravko. (Center for Marine Research, Rovinj, Yugoslavia). 1971. The main features of brachyuran evolution. Syst. Zool., 20:331-340.-Past studies of the evolution of the Brachyura (crabs, Crustacea: Decapoda) have, in general, provided conflicting and unsatisfactory results. This unfortunate situation stems in part from the objective reason that their evolution has been very complex, but, it is also due to the basic inadequacy of the methodological approaches used. Brachyuran evolution has been considered predominantly from only one point of view at a time (i.e., morphological, ontogenetic, etc.) without reference to a synthetic theory of evolution. The present paper attempts to initiate a synthetic approach to the study of crab evolution. The identity of the ancestors of the Brachyura remains uncertain. Nevertheless, it seems obvious that the Brachyura have reached the highest organizational level found among the decapod Crustacea. The genesis of the new organization-brachyurization-involves changes in shape and structure accompanied by maximal diversification or organs and of their functions. This new level of organization has led to great biological improvement as manifested by taxonomic diversity, wide distribution and the ability to leave the primary (littoral) environment. The brachyuran organization is very plastic and has undergone many secondary modifications in connection with further changes of habits and habitats. [Brachyura; Crustacea; evolution.]