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Re: altricial nestling bone fossilization



JH wrote:
  
Check out the following, for instance:
http://www.stanfordalumni.org/birdsite/text/essays/Precocial_and_Altricial.html

>>> This is a great primer on the subject. Very informative. Thank you, Jaime.

  I personally would like to see some demonstrative work on bone formation
or lack thereof in juvenile organisms before conclusions based on
single-person observations are explained as examples of such.
Developmental biology, and indeed, in keeping with evolutionary biology
for the developmental biological evolution synthesis, has held for some
time that bone formation in unsupported young (animals clinging to their
mothers are NOT "unsupported").

>>>>

This will probably come in time.

Responding to D. Marjanovics observation that the wings appear to be capable of 
flying in my neonate reconstructions: That's true. They are full size or 
sometimes larger than their adult counterparts, which seems counterintuitive 
when you consider bat and bird altricial young and their short nonvolant wings. 
[? which means, if I were making this stuff up I would have been smarter to 
make the wing fingers shorter. Again, demonstrating the importantance of 
reporting what is, rather than what should be.] The answer to this apparent 
irony might come in the the explanation for the development of nonvolant 
winglets in longisquamids first reported in Prehistoric Times #64 (also 
available at pterosaurinfo.com).

The bottom line to my questioning is still this: which grows faster? A fully 
ossified bone eroding and redepositing itself? Or a softer sort of bone, held 
together by pterosaurs' unique 'Chinese handcuff/coaxial cable' woven -type 
ossification pattern, loose, poorly ossified and wonderfully expandable at 
first ? increasingly dense and inflexible as maturity (puberty) arrives? What a 
great way to maintain extremely thin-walled bones ? and increase their length 
without epiphyses!

Maybe which grows faster isn't the right question. Maybe pterosaurs and their 
kin simply developed this method out of a number of possible random 
opportunities that were selected for as a result of live birth for some other 
reason as far back as Jesairosaurus. If nest building never was genetically 
encoded into these taxa and they lived in trees, far from dirt and detritus, I 
can see live birth and juvenile hitchhiking as a viable means of ensuring 
continuity. Just a possibility that we can consider.

What predators were climbing through the trees looking for babies in the 
Triassic? I'm not sure I can think of many, other than small lizards and that 
sort, some with gliding ribs.

Just some thoughts.

David Peters
St. Louis