MY THOUGHTS ON THE 'DINO/BIRDS'

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

I have been gone for a few weeks so I am going to put this all in one 
message.  

<<Andre Elzanowski argues that oviraptors and other theropods with 
folding arms are closer to birds than Archaeopteryx, and that they are 
secondarily flightless.>>

Elzanowski has also argued that hesperornithids are the first neognathus 
birds.  

<<It is a fact that many Cretaceous theropods have flight related 
characters (folding arms, large furcula), sometimes the flight related 
characters are better developed than those of Archaeopteryx (large 
sternal plates, ossified sternal ribs, ossified uncinate processes, 
shorter tail, tail with pterosaur-like ossified rods).>> 

Theses features are not as 'well-developed' as Archaeopteryx.  
Archaeopteryx has more avian folding wings due to the shift of the 
glenoid socket, a larger furcula with a more acute angle (not in 
oviraptors), and a *single* sternal unit (contrasted to the two plated 
design of dromaeosaurs).  The ossified sternal ribs are not really 
relevent to flight.  The uncinate processes in dromaeosaurs are 
secondary ossifications (not extentions of the thoracic ribs in 
ornithurine birds).  Archaeopteryx has a tail that is shorter and has 
more closely compressed zygapophyses.  

<<What are we to make of this? I argue that since the Cretaceous 
theropods have both avian nonflight and flight related features not seen 
in Archaeopteryx, that it is therefore very possible that they descended 
from fliers more advanced, and closer to birds, than the urvogel. 
Certainly it is a valid and strong hypothesis, at least as good as the 
conventional view.>>

But you forget the clearly birdlike features of Archaeopteryx:

a)  Loss of the ascending process of the jugal bar.
b)  Loss of squamosal-quadratojugal contact. 
c)  Triangular, crocodilian-type teeth without serrations and ventral 
pits. 
d)  Dorsally placed, prominent acrocoracoid process.  
e)  *Single* sternal unit.
f)  Heart-shaped cuneiform (according to Martin but not to Rick 
Vasquez). 
g)  Dorsal ischial processes.
h)  Reversed hallux (anisodactyl foot).
i)  Caudal vertebrae number reduced to 25-26. 

<<Tom suggested that I favor scenario over phylogentic based hypothesis. 
Nyet! Moi strongly disfavors those who prefer scenario over phylogenetic 
arguments. That is the methodology of Feduccia and Martin. I would never 
argue that some dinosaurs were secondarily flightless unless they had a 
number of avian characters not seen in Archaeopteryx. Both aspects of 
the problem are crucial.>>

I would argue that Feduccia prefers scenario over phylogeny.  larruy 
Martin is more evenhanded and has come up with some really strong 
evidence for his crocodylomorph hypothesis.  

<<As for cladograms and parsimony. I suspect one reason cladograms tend 
to plot Archaeopteryx closer to birds is because they do not include all 
the relevant characters.>>

Are the features stated above irrelevent characters.  These are the 
characters that are not found in any dromaeosaur, oviraptorosaur, 
troodontid, ornithomimid, or tyrannosaur but are found in Archaeopteryx 
and later birds.  Flight characters may not just evolve for flight.  
Climbing and arboreality can account for the flight chartacters.  

<< Also, avian flight characters that are lost along with flight can 
bias the results. For example, flying Confuciusornis had a long, 
strut-like, retroverted coracoid like that of modern flying birds. A 
flightless ostrich has a shorter, broader, procumbent coracoid that 
looks like that of a dinosaur. Yet the ostrich is phylogentically much 
closer to modern flying birds. In losing flight, the ratite coracoid has 
reverted to the dinosaur condition.>>

Lest us not forget that other features support the high position in Aves 
that ratites have.  Ratites show features that are more advanced than 
Confuciusornis, while dromaeosaurs do not show characters that 
*definitely* show that they are more advanced than Archaeopteryx.  The 
retention of the ascending process of the jugal, the 
squamosal-quadratojugal contact, the serrated teeth, the *two* sternal 
plates, and the dorsal ischial processes all suggest that dromaeosaurs 
were more primitive than Archaeopteryx+later birds.  These features are 
*relevent* characters that do not support the hypothesis that 
dromaeosaurs (and other maniraptoriforms) are higher up that 
Archaeopteryx.  

<<Likewise, it is possible that the seemingly less avian - compared to 
Archaeopteryx - coracoids of say dromaeosaurs are actually secondarily 
reversed to the dinosaur condition. Scored on a cladogram, it would plot 
below the urvogel. But maybe its just secondarily flightless.>>

This ignores the features stated above.   

<<So far those doing cladistic studies have completely ignored the 
potential bias introduced by the possibility of early loss of flight. 
Taking steps to negate the bias (by running the character analysis while 
including and excluding flight related characters and seeing if there is 
a difference) should be the norm.>>

The 'flight characters' in dromaeosaurs can be explained by clibing and 
arboreality.  

<<Yet there is little doubt that  the closest relatives of Archaeopteryx 
are dromaeosaurs, they share so many detailed features absent in other 
theropods.>>

There is little doubt that vultures are related to seriemas but they 
went through a touraco clade to get there.  

The features that dromaeosaurs share with Archaeopteryx are primitive 
for Aves and so far nothing has shown that these are not present in 
Caudipteryx.  I do not deny the close relation between dromaeosaurs and 
Archaeopteryx but Caudipteryx can be easily an offshoot of the 
dromaeosaur 'eumaniraptoran' clade.  

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It was also mentioned that feathers "must have evolved for insulation" 
(paraphrasing).  From what I have seen so far, the feathers of 
Protarchaeopteryx and Caudipteryx seem to be for aerodynamics.  They 
cannot be for steering during cursorial activities (as suggested by 
Padian 1997) because of the drag involved.  The aerodynamics were 
probably gliding.  Feathers can be seen in ectothermic animals because 
vultures and kingfishers can raise their body temperature through 
featherd skin (Ruben 1991), yet feathers keep in the heat (Ruben 1991).  

Later,

Matt Troutman

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