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RE: Phylogenetic taxonomic definitions in Xiaotingia paper



David Marjanović wrote:

<Completely new concepts should come with completely new names. Shifting the 
meanings of names around too much increases confusion -- just like inventing 
new names for each tiny shift in meaning would.>

  I do not want to get to the point as in when phylogenetics was introduced to 
mammalian taxonomy, and every new "arrangement" -- excluding this or that taxon 
only from the _topology_ -- came with a new name. It is "okay," right now, to 
shift definitions around, because there is no reason to agree to stability when 
there is no system in place to enforce it. Additionally, we should allow 
ourselves time to find the best internal and external specifiers, and 
definition format for each taxon name we want (node, etc.) so as to permit us 
the most restrictive or open definition we might prefer. And by "we," I mean 
the community as a whole that supports phylogenetic nomenclature (as I do).

<Have you noticed how the term "birds" is used in the discussion triggered by 
*Xiaotingia*? It's used as a branch-based name for everything closer to 
Neornithes than to traditional non-birds like velociraptorines, 
dromaeosaurines, troodontids, oviraptorosaurs and the like. That's how the 
definition of Avialae by Xu et al. maps to their tree. I think Aves should be 
defined that way (more carefully, means, with more external specifiers); that's 
the closest thing to a traditional meaning it has, and it literally means 
"birds" not just in Latin, but also in (higher styles of) today's Spanish and 
Portuguese.>

  This supports the idea that "Aves" should always refer to the esoteric 
"birds." There are only two ways to get around this: Restrict the term to an 
agreed-upon morphological feature or suite, or restrict it to a subset whose 
membership cannot in anyway detract from the definition of "bird." Now, some 
basal avialaeans fall into the concept of "bird" on both aesthetic and 
morphological grounds, but some (e.g., *Shenzhouraptor sinensis* = *Jeholornis 
prima*) do not. This has led to some associating instead the split "Sauriurae" 
and "Ornithurae" with the latter effectively meaning "bird," but still 
including the former in "Aves" because it includes *Archaeopteryx 
lithographica.*

  I will argue right off that, if Xu et al.'s analysis of this particular 
nuance is supported in the future to some robusticity, if *Archaeopteryx 
lithographica* is an anchor for *Aves* in any fashion, all other 
deinonychosaurs should go with it, and I would not quibble that they cannot be 
birds; I would accept the solution, and bluster that everyone should as well 
unless there is better data that says otherwise. Only then does Greg Paul get 
proven right, although under a method he eschewed in the past. The analysis, 
however, is shaky: going through the data in the SOM, I find myself aware that 
minor analytical variations and the alternate close association with 
*Oviraptorosauria* will further support analyses that have also been questioned 
in the past (e.g., Maryańska et al., 2002. Avialian status for 
Oviraptorosauria. _Acta Palaeontologica Polonica_ 47(1): 97-116), even though 
it is unlikely it will support it for the same reasons, as most of Maryańska et 
al.'s original reasons were homoplasious (mandibular "suturing," lateral 
quadrate cotylus for quadratojugal, dentition loss, at least).

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Thu, 28 Jul 2011 11:05:45 +0200
> From: david.marjanovic@gmx.at
> To: dinosaur@usc.edu
> Subject: Re: Phylogenetic taxonomic definitions in Xiaotingia paper
>
> > I'm reading today's posts from the earliest to the latest, so if this
> > has been said, I will hope I am not retreading old ground:
>
> Well, we've all had these discussions several times in the last few
> years, so don't worry about one more repetition :-)
>
> > I'd rather see re-invented definitions of old clade names than people
> > coining new names for new definitions.
>
> Completely new concepts should come with completely new names. Shifting
> the meanings of names around too much increases confusion -- just like
> inventing new names for each tiny shift in meaning would.
>
> Have you noticed how the term "birds" is used in the discussion
> triggered by *Xiaotingia*? It's used as a branch-based name for
> everything closer to Neornithes than to traditional non-birds like
> velociraptorines, dromaeosaurines, troodontids, oviraptorosaurs and the
> like. That's how the definition of Avialae by Xu et al. maps to their
> tree. I think Aves should be defined that way (more carefully, means,
> with more external specifiers); that's the closest thing to a
> traditional meaning it has, and it literally means "birds" not just in
> Latin, but also in (higher styles of) today's Spanish and Portuguese.
>
> > (Mickey, I'm a world-class complainer, and _I'm_ glaring at
> > _you_...)
>
> You're _complaining_ about him. :-)