Re: smallest ANCIENT non-bird dinosaur - was what I was asking

[dinoboygraphics@aol.com]

Had to weigh in here...

Tim Williams wrote:

> Secondly, I'm not at all sure what maximization of either "safe 
inferences" or
> "generalizations" regarding hypothetical ancestors have to do with 
clade
> definitions.  Does this really matter?

Given the history of paleontology and the misinformation given to the 
public I'd say it cannot be emphasized enough how important it is to 
properly gauge(and communicate) our confidence in an inference made 
from extant relatives.  That was the logical underpinning of Witmer's 
EPB framework for soft tissue reconstruction, and it is equally 
important when framing behavioral or physiological hypotheses.  For 
example, consider this Feduccia quote:

"Paleontologists have tried to turn Archaeopteryx into an earth-bound, 
feathered dinosaur. But itâs not. It is a bird, a perching bird. And no 
amount of âpaleobabbleâ is going to change that."

It's revealed as the steaming pile of anti-scientific tripe the moment 
you stop trying to extend the platonic idea of "bird" too far down the 
stem.  The only content-filled part of that statement is that it's a 
perching animal (which turns out not to be correct), the rest of it is 
a rhetorical crutch based on an overt platonic ideal of what a "Bird" 
must be.  Combatting this type of misinformation makes restricitng Aves 
to the crown group not only scientifically useful, but a valuble part 
of a general science education.

> Don't forget that the crown-group Aves
> definition not only casts _Archaeopteryx_ out of Aves, but also 
_Ichthyornis_
> and _Hesperornis_ as well.  We may not be too confident about our 
inferences
> regarding_Archaeopteryx_ (including even whether it flew or not), but 
we are on
> much safer ground when it comes to _Ichthyornis_ and _Hesperornis_ - 
both of
> which would be non-avian under Gauthier and de Queiroz (2001)'s 
definition.

This is the beauty of restricting names like these to crown groups; 
Archaeopteryx is further from the crown clade, so it's obviously more 
tenuous to push inferences that much further.  It IS more likely that 
behaviors or soft tissues seen in modern birds would be found in 
Ichthyornis and Hesperornis, and it's intuitively obvious because they 
are in fact so close to birds, hence (by definition) they share more 
derived features.  Of course you still can't assume features of 
(extant) birds to be plesiomorphic in Ichthyornis  since they lay 
outside the crown group (again rendered intuitive by being close to but 
outside Aves), but the burden of evidence is eased relative to an 
animal like Archaeopteryx.

> I especially like Jeff Hecht's reasoning for why this should be 
avoided.)

I have cut and pasted Jeff's reasoning for ease of reference:

> A general observation in reaction to this discussion -- having watched 
the
> public reaction to astronomers trying to redefine Pluto as a 'dwarf 
planet,' I
> would be wary of the public reaction to attempts to redefine birds in 
a way that
> leaves out Archaeopteryx. Astronomers had a fair justification for 
reclassifying
> Pluto, but they failed completely in justifying it to the public, who 
have long
> been taught Pluto was a planet, and concluded it was hair-splitting 
silliness.
> To the public who pay attention to such things, Archaeopteryx is the 
first bird.
> They would accept a flyer earlier than Archaeopteryx as a bird, but 
they would
> not accept trying to exclude Archaeopteryx on some arcane anatomical 
or
> cladistic grounds. Reclassifying something so fundamental -- and on 
some level
> so obvious -- could make evolution seem a less-certain science than it 
is.

Personally I don't agree with this analogy.  For starters, there hadn't 
been serious discussion of Pluto not being a planet (in the publics' 
eye) until this "controversey" hit the mainstream media, whereas there 
have been people refering to Archaeopteryx as a "feathered dinosaur" 
for decades.  I use it every time I talk to the public on the subject, 
and no one has ever objected in the manner that school children pleaded 
for Pluto.  Indeed, the idea that "birds ARE dinosaurs" has such strong 
appeal to the public that detracters used to accuse pro dino-bird 
scientists of pandering to the public (Larry Martin used to do this all 
the time).  Restricting Aves (and "birds", frankly) only reinforces an 
idea that is already popular with the public while simultaneously 
opening a "teachable moment" to talk about evolution and how out groups 
get succesively more like the crown group the more closely related they 
are.

And finally, planets HAVE to be defined via platonic ideals, because 
they don't descend genetically from other plantes.  You can hash out 
whether Pluto is similar enough in size, mineral composition, and 
formational history to other planets...that is, if it's "planety" 
enough, but it's emphatically NOT the same as classifying things by 
common descent.

Astronomers did it simply because it was more useful conceptually to 
their field.  Not only is is useful to stop extending names in ways 
that lead to unjustified inferences about stem groups, but there is 
immense pedagological and conceptual value in teaching people to think 
this way.  It would be tragic if we didn't have the constitutional 
fortitude to tread where our atronomer brethren have gone, especially 
withe the popular and educational advantages we have.

In short, I have yet to see any arguement in favor of defining 
Archaeopteryx into Aves a priori that doesn't boil down to "I'm used to 
it" (or perhaps, "a lot of people are used to it"), and while there is 
merit in such an argument, I don't think it supercedes the operational 
and educational benefits in this case.


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