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Re: Ceratosauria vs. Neotheropoda?



2009/11/22 T. Michael Keesey <keesey@gmail.com>:
> I can see paraphyletic groups being misused and abused by people who (whether 
> by
> accident or design) equate evolutionary 'grades' with clades, and come up 
> with all
> sorts of spurious phylogenetic hypotheses and conclusions as a result.  Even 
> Paul
> (2008) is somewhat guilty of this, in comparing the evolution of 
> 'iguanodonts' (a
> grade) with that of hadrosaurids (a clade), as if the two groups represent 
> separate
> halves of a whole (Hadrosauriformes), rather than one being a subset of the 
> other.

Fair point: we do want to take what steps we can to avoid that kind of
confusion.

> This could potentially be ameliorated by having a different
> orthographic standard for them. At least one type of paraphyletic
> group has potential here: the stem group including all non-X pan-X can
> be written "stem-X" (where X is a crown clade).

I've seen paraphyletic taxon names written with an appended asterisk
in some contexts (e.g. Colin Tudge's book _The Variety of Life_, which
by the way I heartily recommend).  That seems like a reasonable
approach.  So: Sauropodomorpha, Prosauropoda*, Sauropoda.  I'm not
sold on it, but it seems like an option.

2009/11/22 Michael Mortimer <mickey_mortimer111@msn.com>:
> I'm no fan of BANDits and paraphyletic groups, but I don't see the big worry 
> here.  If
> they define Thecodontia paraphyletically, it will still indicate a limited 
> range of taxa
> that can be used to test phylogenetic hypotheses.  The hypothesis Aves is a 
> clade
> in Archosauriformes that is outside Crocodylomorpha, Pterosauria or 
> Dinosauria is
> just as valid conceptually as the hypothesis Aves is a clade in Dinosauria. 
>  The
> problem with current uses of the term thecodont by BANDits is that they have 
> no
> clear definition of Thecodontia, so include even such non-archosauriforms as
> Longisquama and drepanosaurids.  If they define it, problem solved.

Right -- this seems like a GOOD thing.  Half the reason BANDitism has
clung on as long as it has done is its vagueness.  If its proponents
make the fatal mistake of nailing down precisely what (paraphyletic)
group they think DID give rise to birds, they are suddenly that much
easier to refute.