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Re: up!up!up!and away!
In a message dated 3/21/99 3:07:19 PM Eastern Standard Time,
<< We can speak of primitive and advanced forms of animals, but only in
terms of characters that the animals have - for example the basal form of
an animal is that one that fits all the MINIMUM definitions of the clade,
the most advanced would be the one that maintains all the characters that
keep it in the clade, yet have the most derived versions of those
Is that all or most of the characters that keep it in the clade? This does
raise the question of how many characteristics an animal has to be 'missing'
to be outside the clade. Is there a general principle that says an animal in
direct line of descent (probably) is so different from prior examples that a
new clade is needed?