paraphyletic Rodentia??

[Ken Kinman]

Dear All,
     Thanks for the feedback (public and private).  From what I have been
reading, the question boils down to this:  Is Order Rodentia a paraphyletic
group or is it strictly monophyletic (i.e. holophyletic).  Those who used
the term polyphyletic (even in the 1990's) seem to actually be suggesting it
is paraphyletic.  Unfortunately, students who are taught by strict cladists
do not always learn the distinction between polyphyly and paraphyly, and
since many cladists are taught that they are equally "bad" and equally
"unnatural", there is an increasing tendency to mistakenly say paraphyly
when one means polyphyly, and vice versa.
      Anyway, I will re-read the 1996 paper (in Nature) tomorrow, and read
the 1997 paper (in Journal of Mammalian Evolution) when I can get a copy.
Of course, even if Order Rodentia (Rodentida, if you prefer my
standarardized emendation) turns out to be paraphyletic, I still might not
choose to split it.  It would simply be treated semi-paraphyletically with
markers to show what groups might have cladistically split off between the
sciurognath and hystricognath rodent lineages.  If the paraphyly is
demonstrated and also turns out also to be very complex (rather a simple
paraphyly), then we would have to very seriously consider formally splitting
up rodents.  From what I have read thus far, the data is far too
controversial to even consider splitting the order (and I personally doubt
this will be necessary).
                        --------Ken Kinman
P.S.  Again on the lighter side, it looks as though it should have been
called the "guiana" pig, rather than guinea pig.  More accurate might be
"domestic cavy", or even a native name (if we were not so anglocentric).
But being such a popular pet, the guinea pig will no doubt continue to be
called that in much of the world.  Thank goodness we have the universal
(Latin, Linnaean) scientific name, Cavia porcellus.

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