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Cladistics, on topic



Norman King wrote:

> But it clarifies nothing to say that birds are dinosaurs.  Any child
> can see that birds are not dinosaurs.  Likewise, any child can see
> that whales are not condylarths, although they are members of the
> same clade.
 
The truth of the statement above surely depends on the birds and the
dinosaurs in question. True, the morphologic distance between, say, a sparrow
and a diplodocene may be comparable to that between whales and condylarths.
 But what about the distance between a hoatzin and -Archaeopteryx-? Or, if we
accept the latter as a "bird," the distance between -Archaeopteryx- and
-Compsognathus-? Or between -Archaeopteryx- and the dromaeosaurs?

Having said that, what a child may or may not see is irrelevant; science is
not, necessarily, in the business of "common sense" and many things that seem
to be "true" are counterintuitive (not that children are bound to either
common sense or intuition...) A child might, for instance, have no problem
grouping ichthyosaurs, teleosts, and delphinids together.

> Moreover, while I can show anybody a dinosaur or a bird, you cannot
> show anybody a clade.  I rest my case.

A clade is surely as visible as a class or order.  

I *think* I'm on topic...

Caitlin R. Kiernan