[Taxacom] Defining polyphyly

[Kenneth Kinman]

Hi Stephen,     
       But reptiles do share the defining synapomorphy of amniotic eggs
with birds, basal mammals (monotremes), and almost certainly pelycosaurs
and theraspids as well.     
      As for reptile scales evolving into either bird feathers or
mammalian hair, that has been vigorously challenged.  In any case, I
would find reptilian scales (or any putative derivatives) to be a very
poor synapomorphy to base any reliable conclusions.  They are just too
superficial and of doubtful homology with structures like hair or
feathers.  And I know of no evidence that the first amniotes had scales
or any derivative thereof. 
       The amnotic egg (and its derivatives in therian mammals) seems
far more reliable, along with skeletal morphologies that are better
preserved in fossils than scales, feathers, or hair.  So I am not
convinced that the "other way is also common".   Well, way past my
bedtime and I've had a very long day.   Good night (or "Good Day" to
those of you on the other side of the world).          
           ------------Ken
-------------------------------------------------------------
Stephen Thorpe wrote:     
Well, it can go either way. Perhaps reptiles appear to have no
synapomorphies that birds and mammals don't also have? On the other
hand, I suspect the other way is also common, i.e., suppose
hypothetically that feathers and fur were both transformed reptile
scales, and that the latter is a unique synapomorphy to reptiles, only
it has been transformed to feathers and fur in birds and mammals
respectively, so they (birds and mammals) appear to lack the
synapomorphy definitive of reptiles (i.e., reptile scales).  Stephen 
________________________________ 
From: Kenneth Kinman <kennethkinman at webtv.net> 
To: stephen_thorpe at yahoo.co.nz 
Cc: taxacom at mailman.nhm.ku.edu 
Sent: Wed, 15 December, 2010 4:45:45 PM 
Subject: Re: [Taxacom] Defining polyphyly 
Hi Stephen: 
          Are you sure about that definition of paraphyly? 
Sounds like you are saying that the excluded subgroup (exgroup) lacks
the synapomorphies of the mother (paraphyletic) group, which isn't
necessarily true [for example, the exgroups Mammalia and Aves still
retain the amniotic eggs which characterize their paraphyletic (mother)
group Reptilia].  It is actually the other way around---the
paraphyletic group lacks the synapomorphies of the exgroup.  Or am I
misinterpreting what you wrote? 
          -------Ken