Re: Message from Phil Skell

From: Pim van Meurs <pimvanmeurs@yahoo.com>
Date: Wed Sep 21 2005 - 00:27:01 EDT

Ian Musgrave asked me to post his comments to Skell's message

"The story of Archeopteryx is a classic one in science. It fulfilled a
prediction of general evolutionary theory (as a transitional between
birds are reptiles). It generated two fruitful testable hypotheses
(birds as theropod descendents or birds descended from basal
archosaurs). Concerted anatomical, biophysical, paleontological,
molecular and embryological evidence has been bought to bear on the
problem, with the result that dinosaurian origins of birds is the
favoured hypothesis by a massive amount of data. We are much wiser about
birds, and we know things about bird flight that we would not have known
if not for questions posed by evolutionary biologists."

> The evidential problems most apparent in the Cambrian explosion reappear
> less dramatically throughout the fossil succession.

Ha!

> This is apparent, for
> instance, when we see the enormous work the Archaeopteryx was asked to do
> for one corner of the theory, the idea of the dinosaurian origin of
> birds.
> As Ernst Mayr noted in: What Evolution Is? (2001):

Well, a lot has happened in four years. And there is an enormous amount
of information that was not available when Mayr wrote his book (assuming
the Skell has correctly characterized Mayr's account)

> 1. The dinosaurs structurally most similar to birds are very recent
> (80-110
> million years ago), whereas Archaeopteryx is a great deal older (145
> million
> years ago) and no birdlike dinosaurs are known from the lower Jurassic or
> Triassic that could qualify as ancestors of birds.

Well, as it so happens there are now Jurassic maniraptorans and
dromeosaurs (the groups within which Archeopteryx is placed
cladistically). An exciting spate of recent finds have put a number of
bird-like and feathered dinosaurs much closer in time to Archy (around
125-128 Million years). (Q Rev Biol. 2002 Sep;77(3):261-95.,
Naturwissenschaften (2004) 91:455471, Nature. 2003, 421, 323-4)

Caudipteryx dongi, Shuuvia, Sinovenator changii , Microraptor
zhaoianus and Microraptor gui were all unknown when Mayr wrote his
book (publication schedules being wht they are, some were reprted before
it was actually published). But they have been published now, and one
would have expected even a general scientific reader to be aware of
Microraptor Gui, form the extensive publicity. Why Skell did not refere
to a recent review is beyond me.

> 2. The three digits of
> the hand of dinosaurs are 1,2,3, those of a bird are 2,3,4. It is quite
> impossible to derive the avian digits from those of dinosaurs.

It is quite possible to get avian digits from dinosaur digits,
especially as recent evidence shows that bird digits really are 1,2,3.
(J. Exp. Zool. (Mol. Dev. Evol.) 304B:8690, 2005, J Exp Zoolog B Mol
Dev Evol. 2005 304:206-19. )

> 3.
> Teeth--Theropods have recurved, flattened, serrated teeth, quite
> different
> from the simple peglike, waisted, nonserrated teeth of Archaeopteryx and
> other early birds.

Now found in trodontids as well.

> 4. The pectoral girdle and anterior extremities of the
> late theropod dinosaurs are much too small and weak to have served as the
> foundation of a powerful wing to lift an incipient bird from the ground.

With the discovery of Microraptor and a number of other arboreal
Threopods, there is no need to insist on "ground up" origins of flight

> No
> factors are known that could have caused a sudden drastic growth of the
> anterior extremities.

As we have a number of intermediate forms of varying development there
is no need for drastic growth of these extremities.

> 5. The leading aerodynamic experts of bird flight
> claim that an origin of flight from the ground up is a near
> impossibility.
> (pg. 68).

Well, the dinosaurian origin of birds does not depend on the "ground up"
development of flight. Although recent evidence has suggested that
"ground-up" is quite possible. (Science, Vol 299, Issue 5605, 329 , 17
January 2003)
Received on Wed Sep 21 00:29:48 2005

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