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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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