A quantitative approach to the marsupial brain in an eco-ethological perspective

Using a volumetric method and the classical allometry equation, the author investigates the possibility of a relationship between the size of total brain or brain-components and the ecology of ethology of 29 marsupials species from South-America and Australia. He shows that there is a relation between brain and neocortex volumes, and the taxonomic groups characterized by definite life-habits. New light is shed upon the evolution of marsupials showing that, while the living didelphids most probably are the closest to the ancestral type, some other groups such as the dasyurids and peramelids include even more primitive forms. This points to a very early separation of American and Australian marsupials and to a long independent evolution, perhaps dating back to immediately pre-marsupial times.