Re: [Re: Theory on ornithoptering and could Archie do it ?]

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

<<<Chris: 

The lack of a sternum in Archae is a bit of a red herring.  It is 
probable that the sternum was not ossified, but still allowed muscle 
attachment.  Also, the new form has a small sternum.

 Also it is unlikely that Archae was on the direct line to power flight,
since it lacks a number of critical features such as ligament 
placement.>>>

<<Still, didn't Archaeopteryx show signs of strong muscle attachments 
furcula wise. Sorta showing where large wing muscles started at before 
working their way down. >>


You're pretty wrong in stating this.  Larry Martin has pointed out 
repeatedly that the furcula of Archaeopteryx and the enantiornithines 
was adapted specifically for acting as the major site of the wing 
depresser muscle, the pectoralis.  Previous work done on starling 
furculae by Jenkins et.al. show that the furcuale of modern birds acts 
as a spring-spacer, a necessary part in the wingbeat and lung 
ventilation.  There are exceptions to the rule such as falconiforms and 
parrots where the furcula is to robust for being a spring and too flimsy 
to be a spring respectively.  The main way that the furcula becomes a 
spring in modern birds is its rounded cross-section.  The rounded 
cross-section gives it more flexibility.  However,  the furcula in 
Archaeopteryx and the enantiornithines has a thin,  flat cross-section 
because the furcula is posteriorly grooved.  Why did the furcula have no 
spring in early birds?  According to Martin the design of the 
Archaeopteryx and enantiornithine furcula was evolved to support a large 
pectoralis muscle, the wing depresser.  It makes sense: in modern birds 
the furcula is not the major site for the pectoralis because of its 
spring-like nature (it can't hold much muscle),  but the Archaeopteryx 
and the enantiornithine furcula,  due to its specialized design,  is 
built specifically for accomadating a large,  hypertrophied pectoralis.

So,  as you see,  the furcula of Archaeopteryx is built to hold a large 
wing depresser muscle.  

Matt Troutman

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