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Re: synapomorphies not created equal
Dinogeorge wrote:
Incidentally, any clade is united not by a list of synapomorphies but only
by
a single synapomorphy; in any list of synapomorphies, some must inevitably
be
synapomorphies of nested groups contained in the clade, and others must be
plesiomorphies of clades that contain it. This is because it is extremely
unlikely that a set of apomorphies would all evolve at exactly the same
time.
Not necessarily. Certain apomorphies may be developmentally or functionally
linked. Some dental characters in mammals may fall into both or either
category. The enlargement and aerodynamic refinement of wing and tail
feathers may be both developmentally and functionally correlated.
It has been suggested that the appearance of forward-shifted neural arches
in the caudal vertebrae of titanosaurs might be a correlate of extreme
procoely of the caudal centra. (I would dispute this, however, on the basis
of sauropod taxa that show one of these apomorphies, but not the other.)
Tim
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