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Re: Dinosaur beaks



Jaime wrote: >>> The sheathing of the scales does not permit them to be 
preserved around the body, even as impressions, and rarely as an outline. Does 
this mean they were naked-skinned? <<< 

How this statement is related to anything I stated previously is lost to me... 
It is I that stated that making jumps in conclusion based on what is preserved 
and what is not is at best arm chair conjecture. When it comes to preservation, 
we see very odd events if we are looking for a basic standard. Skippy is all 
guts and pretty much zero integument. Skippy was not produced by magic but by 
the local conditions that may not even have existed just a few feet away. Or, 
these conditions could have also been quite common for miles around. Who knows. 

As stated before, modern birds have varying forms of prokinesis that allow the 
premaxilla to act as a sort of manipulation tool not seen in basal forms. In 
parrots, this joint has become a completely diarthrosis style joint. In basal 
birds like *Confuciusornis*, this was not the case, and few signs of the later 
advanced prokinesis are seen. Trying to draw correlation's between modern birds 
and their basal counterparts avoids huge amounts of selection over millions of 
years. 

But even still, we see an increase in the size of the premaxilla in 
*Confuciusornis* as well as the lateral movement of the nasals. This is closer 
to what we see in modern birds. Since it is the premaxilla that is being 
claimed here to have had a rhamphotheca, it would be easily derived that this 
basal bird would have had a much larger rhomphotheca in general, relative to 
other basals... Hence, a higher degree of preservation. Even though the 
premaxilla is much larger in this animal, we still find beak preservation rare, 
with the amount not preserved being larger by far than the region hypothesized 
to be present in animals such as *Archaeopteryx* and *Microraptor*. 

Let's not debate negative evidence, but wait for the fossil record to explain 
our ignorance. 

Kris