The platypus, apparently, is a surprisingly deep sleeper. What's more, it
             spends more of its time in so-called 'REM' sleep than any other mammal.
             These are the conclusions of a study on sleep in the platypus by Jerry M.
             Siegel of the Sepulveda Veterans' Affairs Medical Center, North Hills,
             California and colleagues. Their report appears in a special number of
             Philosophical Transactions of the Royal Society devoted to the biology of
             the platypus (Ornithorhynchus anatinus), celebrating the bicentenary of the
             discovery, in Australia, of this remarkable animal.
             'REM' stands for 'rapid eye-movement' and is the kind of sleep in which the
             brain can be more active than in it is while awake, the animal twitches, and the
             eyelids flicker – hence the name. In humans, REM sleep is associated with
             But does the platypus have an extraordinarily rich dream life? Possibly not,
             say the researchers: "cats, opossums, armadillos and other mammals not
             known for their intellectual achievements have far more REM sleep, whether
             calculated in hours per day or as a percentage of total sleep time, than
             And why study sleep in the platypus anyway? After all, the platypus is an
             obscure and extremely primitive creature, distantly related to humans. The
             answer lies in that primitive state: studying the physiology of the platypus could
             yield clues about the life and behaviour of the very earliest mammals.
             The platypus belongs to a group of mammals with very ancient roots. Apart
             from the platypus itself, the group – the mono...