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RE: titanosaurs



Dinogeorge wrote:

> At least in molecular cladistics an equal weighting scheme is 
> reasonable, since the four bases of DNA have a practically even chance 
> of being at any particular locus.

Oh dear me, nothing coud be further from the truth.  There's a LOT going on
at the molecular level, and one cannot never *assume* stationarity.
Synonymous codon usage in genes and secondary structure of ribosomal RNA are
just two examples of why the four bases DO NOT have a practically even
chance of being at any particular locus.  I could go on, but this is way
off-topic.

> E.g., if morphological cladistic analysis contends that avian flight 
> developed from the ground up, this disagrees with physics and 
> functional anatomy, and perhaps we should rethink the cladistics, not 
> necessarily the physics or the functional anatomy. 

An interesting exam question: "In 1000 words or less, please list and
describe all the errors present in the above statement." 
 
I'll mention a few... 

1) Current theropod phylogenies are amenable to either a "ground-up" or a
"trees-down" origin of avian flight.   

2) For the thousandth time (and counting), the traditional "ground-up" vs
"tree-down" dichotomy is an outdated mindset.  As Padian and others have
stated _ad nauseum_, there is no compulsion for a hypothetical pro-avian to
adhere exclusively to a terrestrial or arboreal ecology.  

3) Physics and functional anatomy have yet to disprove a gravity-opposing
("ground-up") origin of flight.  Sure, it's more challenging that a
gravity-assisted origin of flight; but as long as its physically feasible,
it's on the table.  Evolution does not have to take the "easiest" course; it
can only act on the raw material available.

4) Heck, insects did it.  The available evidence (fossil, functional
anatomical, experimental) indicate that insect flight arose without the
assistance of gravity.




Tim