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Re: Ceratosauria vs. Neotheropoda?



2009/11/23 David Marjanovic <david.marjanovic@gmx.at>:
> All those biodiversity studies from Jablonski to Benton. They count genera,
> families, or even orders and then use those numbers in the assumption that
> they represent any kind of approximation to a measure of biodiversity. That
> simply isn't so. Orders, families [...] are simply not
> countable. One reason for that is that they don't need to be monophyletic.

Monophyly also has nothing to do with countability.  In what sense is
the clade Theropoda "comparable" with the clade Apatosaurinae.  It
should be pretty obvious that when people count families and other
rank-based taxa in diversity studies, they are using them as
rough-and-ready proxies for either specific/generic-level diversity or
morphological disparity.

Not that I am saying "families" or similar are necessarily GOOD
proxies for either diversity or disparity (they are in some taxa, and
not in others).  But their utility or otherwise for this purpose is
completely unrelated to their monophyly or otherwise.

> Here's another: Why can't we recognize a group for egg-laying synapsids (an
> example that comes up on this list every few years) if that's interesting in
> the context of our ecological question? Only because it would overlap with
> Mammalia, never mind the paraphyletic Reptilia, and we can't have
> overlapping taxa in rank-based nomenclature.

You are conflating two completely unrelated traditions of
pre-phylogenetic nomenclature here: the acceptance of paraphyletic
taxa (which I support) and the idea that taxa of a given "rank" may
not overlap (which I do not support, since I don't accept rank in the
first place).  There is not the slightest reason for thinking that
someone who accepts the former also subscribes to the latter.

> We actually _want_ to talk about phylogeny, and
> that only works if we can name every clade we find interesting, without
> names for grades getting in the way. This is probably the most important
> reason why the PhyloCode doesn't allow paraphyletic taxa to have an official
> name-definition combination.

This is a complete non-sequitur.  Formally defining a paraphyletic
Prosauropoda would not in any sense "get in the way of" the clades
Sauropodomorpha and Sauropoda.