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Re: Tucson Tales III.

Paul Janke wrote:
 > Stan Friesen wrote:
 > >Actually, the main reason that the cursorial theory was even
 > >considered is that Archeopteryx appeared to be a terrestrial
 > >runner, not a tree dweller.
 > You're being very kind to the "cladist" camp. To whom did Archie
 > appear to be a terrestrial runner and not a tree-dweller?
 > The ornithologists such as Martin and Feduccia have long maintained
 > that Archie exhibited arboreal characters(not the least of which is
 > flight feathers).  They refused to ignore the arboreal evidence in
 > spite of the widespread acceptance of the therapod-bird hypothesis.

You again seem to be making the error that the theropod-bird theory
requires a non-arboreal origin of flight.  One of the main points
of my article is that it does not.  An arboreal origin is quite
consistant with a theropod origin.

The fact is most of the thecodont groups considered as candidate
ancestors also consist mostly of cursorial ground-dwellers, so the
basic issues reamin the same.  Even among the crocodilians and
close relatives, the forms usually considered for avian ancestry
are cursorial, as must be since the known alternatives are all
ground-dwelling *quadrupeds*, which is even further from the avian
anatomy.  (The majority of the pseudosuchians and crocodilians
are quadrupeds).

The problem with Martin and Feduccia is that they were unable
to demonstrate any of these arboreal features clearly until
recently.  Merely stating 'it looks arboreal to me' doesn't
cut it, clear comparative evidence is required.

The fact is that Archie has legs similar in shape and size
to those of cursorial bipedal archosaurs, so a cursorial
life style seems a reasonable conclusion.  That remains true
even now - Archie probably was a good ground runner that used
trees as a launching platform, and perhaps a nesting site.
[One of the big advantages of birds is their ability to put
nests in inaccessible places to protect the young from ground
dwelling carnivores].

 > ---
 > Stan Friesen wrote:
 > ...  This changes the balance, and suggests that the arboreal
 > >model is pefectly consistant with A. as an early bird, *and* with
 > >the dinosaurian origin of birds.
 > Everything you say here is consistent with Feduccia's study except
 > the part about changing the balance and the part about the
 > origin of birds. Feduccia never thought any balance needed changing,
 > he recognized the arboreal characters of Archie all along.

But is does change the balance.  Until he published that article
he had no *solid* evidence.

 > This study
 > just adds one more arboreal character to an already extant list that
 > Feduccia and Martin have been expounding for years. Maybe it changed
 > the balance for you and others, but to be fair, no balance needed
 > changing for the ornithologists. I wouldn't be surprised if the wild
 > cursorial theories that were becoming widely accepted actually
 > Feduccia to pursue this line of research, all the time knowing in
 > own mind that the evidence points to an arboreal Archie.

I agree that the cursorial origin models were all a little strained
and are well abandoned.
 > With respect to the dinosaurian origin of birds, Feduccia says:
 > "If Archaeopteryx lived in trees, it means that it evolved not from
 > dinosaurs as most paleontologists currently believe, but from some
 > tree-dwelling reptile, since dinosaurs lived on land and not in

This is not clear.  The anatomy of all the known non-flying bipedal
archosaurs is that of a ground-dwelling runner.  So, what *other*
archosaurian group does he suppose was 'more arboreal' than the
theropod dinosaurs?

The fact is there is *no* known archosaurian group with known
arboreal forms suitable for avian ancestry.  The only one I know
of is Longisquama, which is quadrupedal, and thus not a good
candidate for adirect vian ancestry.  Thus, the same 'problem'
with arboreal versus cursorial forms is present in every good
candidate group.

Now, *if* Protoavis is, in fact, a single organism, *and* it
is arboreal, then we have exactly one candidate for an arboreal
bipedal archosaur.

In short, if pseudosuchian or protosuchian archosaurs could
evolve arboreal forms from cursorial forms, so could the

 > ---
 > Stan Friesen wrote:
 > >
 > >I don't know, since those results you mentioned are all very recent
 > >are you sure the non-arobreal theory still has many adherents?
 > They haven't thrown in the towel yet, although Ostrom is softening
 > up a bit. He says "I think Alan has put together a very solidly
 > study. I'm not set in concrete." (from Science News, Feb 6, 1993)
 > I can't find a reference at the moment but I recall either Padian or
 > Gauthier coming out swinging against Feduccia's paper last year.

Perhaps.  Padian seems a little too rigid to really evaluate
the evidence clearly.

 > The "cladists" in this example
 > thought they could use their model to infer something beyond it's
 > scope. They ended up endorsing a cursorial origin of flight,
 > that required that they ignore hoatzin-like wingclaws, upright
 > flight feathers, and now perching-type footclaws in Archie.

Well, the hoatzin-like claws are only obvious in retrospect,
the presence of claws could equally simply have been a retained
ancestral trait of little adaptive significance - that is they could
have been vestigial.

And, until Feduccia published his study there was little evidence
that the footclaws were perching-type claws.  These things are not
as easily determined as it might seem to the outsider.  I had to
read Feduccia's article before I could evaluate the evidence,
and despite Padian's opposition, I found his evidence quite strong.

Again, just because Martin and Feduccia's gut feeling has now been
largely vindicated does not make the non-arboreal idea retroactively
unreasonable.   It is unreasonable *now*, but it was not so before.

In general it is often the case that new evidence makes previous
theories look silly.  This does not necessarily mean they really
*were* silly when first proposed.  Inheritance of acquired characters
appears stupid now, but prior to the discovery of genetics it was
one reasonable theory about the origin of variation.

swf@elsegundoca.ncr.com         sarima@netcom.com

The peace of God be with you.