DINO/BIRD MANI

["Matthew Troutman" <m_troutman@hotmail.com>]

<<To me, an interested, and I think, reasonably intelligent outsider (an
ecologist), Feduccia and colleagues have done what scientists are
supposed to do. They have produced an observation which tends to
negate an hypothesis that was advanced to explain an observation.
Padian, et al., have done what they were supposed to do, i.e., scramble 
around to find an explanation which accommodates the new data but saves 
the hypothesis.  It seems to me, however, that Padian and others have 
had to scramble quite a bit and resort to some unstraightforward 
explanations to reconcile the bird and dinosaur hands.  Parsimony would 
favor Feduccia here, but Padian may still be right. I await more data.>>

I certainly agree with you that Feduccia et al. ( actually it should be 
Martin et al. ) have done the scientific thing to do.  They certainly 
made the list scramble a few months ago.  However, personally, a lot of 
the things that Feduccia says and does in the dino/bird debate can be 
considered unscientific.  When he commented on Sinosauropteryx feathers 
without ever seeing a picture of it.  He fails to note contradictory 
evidence to his origin of birds hypothesis; the Megalancosaurus and 
avimorph hypothesis ( Megalancosaurus is almost certainly excluded from 
candidacy of avian ancestor by its lacking of a quadratojugal among 
other things ).  Feduccia fails to acknowledge the large amounts of 
osteological, behavorial, myological, and eggshell evidence that shows 
that birds are related to dinosaurs.  Larry Martin on the other hand has 
been relatively even-handed in his arguments against the dino/bird link 
and has come in support of the only other viable candidate for an avian 
ancestor; a crocodylomorph. 

DINO/BIRD HANDS

The thrust of Burke and Feduccia's argument against the dinosaur/bird 
link concentrated on the primary axis of cartilage condensation in the 
avian manus.  They showed that in all tetrapods that digit IV, in both 
the manus and pes was the first digit to appear and that its cartilage 
travelled medially and laterally to the other digits. Digit IV is always 
opposite the ulna in all tetrapods and it recieves its cartilage from 
this part of the limb bud.  The evidence would seem to support that the 
digits in birds are II-III-IV because there are similiar developmental 
patterns in other tetrapods such as turtles and crocs.  However, the 
problem is that in maniraptoriform theropods, digit III is opposite the 
ulna.  The reason why digit IV in other tetrapods is the primary axis is 
because it is opposite the ulna where it gets its cartilage.  Since in 
theropods digit III is opposite the ulna, then it is concieveable that 
digit III is the primary axis in theropods and birds.  Really the paper 
was just a review of the development of the manus in tetrapods; it 
introduces no new information to the dinosaur/bird debate.

Matt Troutman

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com