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RE: a rose by any other name(was fish & dogs)

Just a little tidying-up to do...

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Mickey_Mortimer
> Thomas Holtz wrote-
> > Are _Ichthyostega_ and _Acanthostega_ and _Panderichthyes_?
> Man, I hope those aren't dinosaurs, or else I'm behind on my
> references once
> again! ;-)
D'oh!  I meant to write "are _Ichthyostega_ and _Acanthostega_ and
_Panderichthyes_ amphibians?"

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> King, Norm R
> >Perhaps we have a difference of definition here.  When I said that
> "evolutionary lineages were the only real thing there" (the
> context was with
> regards to "species definitions" vs. "higher order taxa"), I meant this:
> Evolution happens.<
> Actually, I am certain that my comment in those posts a few years ago were
> not in reference to anything Tom said.  I am sure it was someone in Texas
> who made the stronger statments I objected to.

Sorry, my bad.  Thought it was a reference to an earlier comment I had made.

> From: philidor11 [mailto:philidor11@snet.net]
> Mind if I begin with a compliment?
> You write cogently, you understand the prior argument, you
> respond directly,
> the information you introduce is pertinent, and your arguments reach
> conclusions related to the topic.
> You might have been an English major.


> So, the thorough application of logically consistent ideas
> produces an idea
> of birds strongly at variance from the popular idea.  Do you
> -stick to principles or compromise by carving birds out of dinos
> (and dinos
> out of reptiles, another parenthetical ghost),

I, personally, stick to my principles

> -and if you stick to principles, do you attempt to persuade the public to
> agree with you, or acknowledge the popular approach when speaking to the
> public, but use the different logic within the field?

I, personally, attempt to persuade the public to agree with me.  Hence my
corruption of the innocent youth of the U.S., Canada, and the U.K. by
introducing a phylogenetic taxonomic definition of Dinosauria to kids in
(among others) Brett-Surman & Holtz's James Gurney: The World of Dinosaurs;
the multi-authored Dinosaurs of the World series (darn publishers never did
send me a set, and now its out of print!!!); and the forthcoming Little
Giant Book of Dinosaurs.  Hey, I also discuss the nasty e-word (Evolution)
in these books, too.

(And, of course, for older audiences there are venues such as teaching,
public talks, and internet lists...).

> <Any time you get near the base of a well-known lineage there is some
> question as to whether a particular taxon belongs in that named group or
> not.  (This is less problematic if the taxonomic scheme has rigorous
> organizing principle, and more problematic when multiple (or no)
> organizing
> principle is used).>
> Less problematic, then, but still problematic, as shown by your list of
> examples and the endless discussions of the coding and relative
> significance
> of characters of basal whatnots here on the list.  If the
> greatest weakness
> of a classification system which carves out groups of species (I know, but
> taxa are right up there with bosons in public understanding) based on
> obvious differences from other species is fuzzy examples at the
> margins, if
> that's the controlling argument, then the superiority of a phylogenetic
> taxonomy is a very fine distinction, uncompelling for marketing purposes.

Actually, for the cases I listed, one CAN decide whether the particular taxa
belong in a particular clade or not using phylogenetic taxonomic principles,
but their inclusion or exclusion from the traditional versions of the clade
is problematic.  So we could exclude _Lagosuchus_ from Dinosauria (as most
workers did) or include it (as did Bob Bakker and Greg Paul) based on a
gestalt version of Dinosauria.  However, if we define Dinosauria under a
particular PT definition (e.g., all descendants of the most recent common
ancestor of _Iguanodon_ and _Megalosaurus_), than _Lagosuchus_ can only be a
dinosaur if it falls within said clade (which, independant analyses agree,
it does not).

> You did confuse me a bit when you said:
> <This [one can test whether a critter belongs in a taxon or not] is also
> true for systems that might use a particular suite of defining
> (rather than
> merely diagnosing) traits: if the critter has these traits, it is a member
> of that clade; if not, it ain't.>
> The distinction between defining and diagnosing...
> Also, implicit here is that the identifying information is primarily based
> on observation (has traits/does not have traits) rather than history (is
> related to _because_ the animal has certain traits hypothesized
> to indicate
> an evolutionary relationship).  Once you have said observation is
> acceptable
> in classification, and suites of related traits do also bring in function
> and other non-historical judgments, then are you far from saying
> birds are a
> recognizable group?

Actually, I was arguing here that phylogenetic taxonomy is not the only
scheme with a central organizing principle.  One could, in theory and in
practice, develop a taxonomic scheme that is based on morphological
disparity: this has been proposed, and some people have even been claimed to
have been using it, but in practice they were for the most part simply
relying on the authority-based system, and finding justifications for it.
(Another model that did have an organizing principle based on morphology,
phenetics, also had a brief life in the systematics world).

So, yes, there are alternative systems one could employ that are logically
consistent.  However, I would then argue (redundantly, as this debate was
fought and wone during the 1970s and 1980s...) that propinquity of descent
rather than morphological disparity represents a more informative binding
principle for a variety of reasons.

> In fact, being facetious and taking a comment out of context, doesn't
> saying:
> <...[Aves] is the clade comprised of all descendants of the most recent
> common ancestor of living feathered
> vertebrates, in which case the Mesozoic taxa I listed are NOT birds...>
> match the popular definition and resolve the fuzzy examples problem,
> assuming Aves were at the level of Reptilia?

This doesn't match the popular definition, since most people consider
_Archaeopteryx_ an ancient bird, yet _Archaeopteryx_ is not a bird in the
above definition.  (This is of course leaving aside the fact that most
people consider pterodactyls ancient birds, too...).

> I'm also trying to catch up with your meaning when you say:
> <Would Prof. Big (who may be dead, making him difficult to reach) include
> _Nova taxon_ in his Taxomorphoidea or not?  Do we expand Taxomorphoidea to
> include it, or create a taxon of equivalent rank for it, or what?>
> then note later:
> <We could argue whether "bird" technically applies to the clade Avialae
> sensu Gauthier ... or if "bird" applies to Aves sensu Gauthier ...>
> it sounds like Gauthier is equivalent to Prof. Big as far as
> Avialae/Aves is
> concerned.  Does having algorithms really eliminate the existence of sensu
> somebody?

Sorry about that: I was using shorthand here, hoping people on the list were
familiar with the definitions that Gauthier originally proposed (Avialae as
Aves and all taxa closer to it than to deinonychosaurs; Aves as all
descendants of the most recent common ancestor of ratites, tinamous, and
neognaths).  In the phylogenetic taxonomic system, the statement of ancestry
is the algorithm used.  Of course, someone first has to propose it, but then
it should (in principle) remain.  In contrast, an authority-based system
works on the principle of (pardon the temporary blasphemy...) "What Would
Simpson Do?" (or insert other authority in G.G.'s place).  Would Simpson
have included this new little fuzzball in Allotheria?  Would this new
ornithopod fit Lull & Wright's concept of Hadrosauridae, or Weishampel's, or
Horner's diphyletic hadrosaurid concept?

Hope this helps,

                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
                College Park, MD  20742
Phone:  301-405-4084    Email:  tholtz@geol.umd.edu
Fax (Geol):  301-314-9661       Fax (CPS-ELT): 301-405-0796

> -----Original Message-----
> Mickey Mortimer