On 04/12/2010 12:57 PM, andrel wrote:
> "Birds are dinosaurs, and dinosaurs (except birds) are reptiles, hence
> (sorry no hence)."

  Dinosaurs belong to the class reptilia, and theropods are a suborder
of dinosaurs, hence theropods are also reptiles. If birds were
theropods, they would obviously also belong to the class reptilia.

  I'm not sure where you are conjuring that "(except birds)" thing. Why
is it ok to say "birds are not reptiles" but not to say "birds are not
dinosaurs"? Why do you draw the line between dinosaurs and reptiles
rather than between birds and dinosaurs?

>>   If birds were - indeed - dinosaurs, that *would* make them reptiles
>> because dinosaurs are classified as reptiles. However, birds are *not*
>> classified as reptiles. Hence birds are *not* dinosaurs.
> 
> A good example why paraphyletic groups are not a good idea. It leads to
> logical inconsistencies like this.

  It's not a logical inconsistency. You simply say "birds are not
dinosaurs" and everything is consistent.

>>   Just because birds *evolved* from dinosaurs doesn't change that.
> 
> No, but changing definitions of what a dinosaur is might.

  But why do you want to change the definition of "dinosaur" rather than
keep the current definition of "bird"? Why do you want to cut the
relationship between birds and reptiles between the dinosaur-reptile
classification, rather than between the bird-dinosaur classification?
The latter would be much more logical.

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