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Re: T-J Extinction event article (more media errors?)
In a message dated 5/12/01 4:39:39 PM EST, tmk@dinosauricon.com writes:
<< What I want to know is why you consider turning traditional taxa into
stem-based clades more elegant than turning them into crown clades? >>
Crown clades are an accident: the (supposedly) fortunate lineages that
happened to have survived to the present. Why should this be the criterion
that determines where we cut off for Mammalia? By tradition, the amniotes are
divided into three subtaxa: reptiles, birds, and mammals. Why not let each
subtaxon extend as far down its phylogeny as possible, until it contacts its
common ancestor with one of the other subtaxa? We already know that birds are
themselves a subtaxon of reptiles, so let's let the reptiles and the mammals
extend down to their common amniote ancestor. For that matter, we might even
let reptiles extend all the way down to their common ancestor with
amphibians, which would make mammals a reptile subtaxon, too. It's just as
workable as any other scheme.