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"Primitive" marsupials?



I apologize if this is off topic.

Occassionally the topic of relative predatory abilities of marsupials and
placentals has come up.  Usually this is in reference to the distribution
of avian species.  I thought I would alert those interested to a new book:

Aitkin, L 1998 Hearing--the brain and auditory communication in
marsupials. Springer-Verlag, Berlin.

While mounting a good defence against charges of "primitiveness" of the
marsupial brain, the author concludes: "...audiograms of marsupials
indicate a range of sensitivities comparable to eutherians, but they
appear generally less sensitive, either in minimum threshold or in range
of frequencies."  This is particularly true of high range.  High range is
helpful in hearing movement through grass and the fluttering of wings.  In
this respect, studied marsupial carnivores do not compare well with cats.
Left open is the grand question : whether such deficits are due to
different niche requirements (i.e., marsupials need other ranges
emphasized) or some developmental constraints in marsupial embryogenesis.