Re: NO SECONDARILY FLIGHTLESS THEROPODS

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

<< I have to say you have greatly weakened the neoteny case by admitting 
that penguins are a counterexample.  Although I can't give numbers of 
individuals, there are a great many more penguin species than ratites. 
Whatever the figures, penguins are a valid counterexample, and only go 
to show that if a development such as flightlessness has a particular 
specialised use, it may also have a particular specified mechanism - 
neoteny when it suits, otherwise when it doesn't.  Your claim that 
penguins are a special case supports my argument better.>>

     But, as I said before, penguins still "fly". They use their 
forelimbs as "wings" just in the same way as volant birds. Their 
musclature is still stronger than flying birds. They are not flightless, 
they still do fly.

<<Some penguins have really rather long forelimbs, and I find the 
attempt to use the large forelimb of dromaeosaurs as evidence against 
loss of flight far from convincing.>>

     See above.



>2:  _Archaeopteryx_ shares too many features with modern birds that
>     e.g. dromeosaurs don't.

<<As far as the head is concerned, I see no reason to doubt the 
proposition that Archy almost always ate prey much smaller than itself 
and didn't need to do much heavy dismembering of large prey.  The 
opposite is probably true of dromaeosaurs.  Droms' teeth had to force 
their way deep into flesh, enlarging the holes in the process to help 
the holes merge together to form strips.  It is quite likely that Archy 
(and other early birds) simply used them to increase the friction 
between the prey and its jaws.  For this reason, their teeth were 
relatively small and unserrated.  Droms' serrations were probably due to 
re-activation of the original genetic mechanisminherited through Archy 
etc from earlier times, but failing that, if they were evolved once, 
they could have been evolved twice.>>

This is hardly convincing. It still doesn't explain the other dozen 
characters that say that it couldn't evolved into dromaeosaurs. 


<<  Wouldn't we expect to find under these
circumstances exactly the same type of confusing mosiac of partial
inheritance that troodonts and droms. show?>>

     This assumes a lot on the behavior of the ancestors of the two 
groups.



>>However, these two conclusions have many faults. First of all,
>>dromaeosaurs have no features that can be considered more
>> advanced than Archaeopteryx ( except for perhaps the sternal size
>> and pubic retroversion ).

<<Ah well - except for them!  Pubic retroversion - a minor point?  And 
lets not forget uncinate processes which really ARE useful relationship 
pointers because they're almost never lost.  (No ribs found for "Rahona" 
but the metatarsals, though unfused, are more constricted distally.)>>

     Pubic retroversion and postion is variable in living birds.

>> All of the best recent finds of
>> dromaeosaurs and Archaeopteryx suggest that Archaeopteryx is
>> more birdlike than all known dromaeosaurs.
>
<<. . .but only in easily reversed features  (e.g. the reversed distal
hallux).>>

     Easily reversed? Even in pamprodactyl birds the hallux is still 
reversible.


<<But of course the biggest justification for K-BCF is all the features 
that are:

*  Totally understandable in terms of flight>>

   Or climbing.

<<*  Totally incomprehensible in any other reasonable terms>>

     Not so.


These various replies are making me >consider< _NO SECONDARILY 
FLIGHTLESS THEROPODS II ._

MattTroutman

   

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