Re: Strange thoughts on PN - was Re: BAD vs. BADD

[dinoboygraphics@aol.com]

> > > Canidae are a rather clear-cut group now-adays, as are primates, 
perissodactlys or whatever.<<<

Well first of all, I'm pretty sure that all of those examples are 
actual monophyletic groups, so I'm not sure how they serve your 
arguement.  If you are claiming that non-avian dinosaurs are in some 
way as real or useful a group as monophyletic Canidae, then I think you 
are highlighting the flaw in the idea of using arbitrary groups.  
Second (this has been mentioned by David), but the problem in that 
statement is "now-adays".  Sure some people only work with extant 
birds, and some only work with one or another group of extinct 
dinosaurs (avian or otherwise) but to name them as separate 
non-phylogenetic groups is to encourage people to use the wrong 
inference when trying to reconstruct missing morphology, soft tissue 
anatomy, and even phylogeny (because it's human tendancy to assume that 
the characters that "unite" the organisms into said group have 
phylogenetic value).

> > > Perhaps it is just my insufficient knowledge of animals, but doesn't 
it seem as if the majority of animals can easily be grouped by their
morphology? And isn't it somehow dangerous to claim that all this is 
arbitrary and worthless if it is so easily observed? (See below for an
example.)<<<

It only seems like that when there are large gaps created by holes in 
the fossil record.  There is no morphological basis to claim that 
Jeholornis is meaningfully "undinosaurish," yet it's closer to birds 
than Archaeopteryx.  The record of paleontology is littered with bad or 
missed interpretations because people assumed that "reptillian 
dinosaurs" wouldn't have air sacs, or feathery integument, etc.

Inprimataology, the assumptions that "pongids" (orangatans, gorillas 
and chimps) were "meaningfully" closer to each other than to humans 
caused anthropologists for decades to not see the obvious similarities 
that chimps and people share to the exclusion of other apes,  including 
group behavior, reproductive behavior, cultural transmission, tool use, 
etc.  And of course it explains why chimp immune systems are so much 
more similar to ours than are other "pongids".  While our stance and 
reduced hair thickness (people still have lots of hair in terms of 
strands per unit skin surface, it's just shorter and finer than the 
other apes') make us look superficially "more different" from other 
apes, grouping us according to this non-phylogenetic arrangement has 
lead to decades of muddied attempts to understand ape biology 
(including our own) that is only now getting cleared up.

Another example would be when people split up deuterostomes to discuss 
"invertebrates" vs "chordates".  It might seem morphologically 
"meaningful" to say that in many ways echinoderms and hemichordates are 
more like other invertebrates than they are like vertebrates, but then 
we would be ignoring developmental and molecular pathway similarities 
that show otherwise.

> > > Shouldn't there be a clear-cut systematic way to talk about the set 
"bony fish" without Tetrapodes? Do you really say that this grouping is 
worthless because we know of perhaps a handfull of fossils (from 
probably more than 50000 fish species known all together) that would be 
difficult to place? Isn't it intellectually even more misleading to 
tell people: No there is no such thing as bony fish, unless you
include humans?<<<

First of all, why is this useful?  You can still talk about (or study) 
any group you want, regardless of its phylogenetic validity.  No one is 
preventing researchers from doing a review of basal iguanodontians; 
we're just argueing that there is no need for a non-phylogenetic 
nomencalture.  Such a system would be cumbersome (a whole different 
system to remember!), and I'm yet to see why it's useful, outside of 
shortening a few sentences in conversation.

As for your fish example, I personally find it is more intellectually 
dishonest to refer to a group that places dipnoans, rhipidistians, 
rhizodonts, and stem group tetratpods alongside trout to the exclusion 
of amphibians, rather than to simply say that tetrapods are a type of 
sarcopterygian fish.

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com

-----Original Message-----
From: martin.baeker@tu-bs.de
To: dinoboygraphics@aol.com
Cc: dinosaur@usc.edu
Sent: Wed, 23 Aug 2006 12:31 AM
Subject: Re: Strange thoughts on PN - was Re: BAD vs. BADD



BTW, I think two different things are frequently confused here: One is 
this
type of "grouping-by-morphology" (lumping all dog-like mammals as
Canidae etc.), the other is assigning ranks to these groupings.
(Seems I was myself guilty of this in a previous post...)  For the
ranking then leads to trouble if one group splits much more than
others do (wasn't it once said that insect orders are more like
vertebrate classes?).

> It may be "unwelcome" to some (maybe even
> most) people to have to use terms like "non-avian dinosaurs" or 
"non-human
> primate", but using them encourages us to be intellectually honest, by
> reminding ourselves that the group is arbitrary, and that we must be 
careful
> to ensure that the characters under discussion are actually 
restricted to the
> group at hand, not simply an illusory lumping of characters from 
animals we
> asssume are "alike" in some way.

Shouldn't there be a clear-cut systematic way to talk about the set
"bony fish" without Tetrapodes? Do you really say that this grouping
is worthless because we know of perhaps a handfull of fossils (from
probably more than 50000 fish species known all together) that would
be difficult to place? Isn't it intellectually even more misleading to
tell people: No there is no such thing as bony fish, unless you
include humans?

Cheers,

Martin. (Who still tries to form an opinion on all these things.)

                  Priv.-Doz. Dr. Martin BÃker
                  Institut fÃr Werkstoffe
                  Langer Kamp 8
                  38106 Braunschweig
                  Germany
                  Tel.: 00-49-531-391-3073
                  Fax   00-49-531-391-3058
                  e-mail <martin.baeker@tu-bs.de>

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