The Short-beaked ORGANIZATION@1 has the largest prefrontal cortex with respect to body size of any mammal , it shows rapid eye movement during sleep , and its brain has been shown to contain a claustrum that is similar to placental mammals , linking this structure to their common ancestor .

The Short-beaked ORGANIZATION@1 has the largest prefrontal cortex with respect to body size of any mammal . It shows rapid eye movement during sleep , and its brain has been shown to contain a claustrum that is similar to placental mammals , linking this structure to their common ancestor .
