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Fw: Re:avian flight



 
----- Original Message -----
From: calzola
Sent: Sunday, January 14, 2001 4:04 PM
Subject: Re:avian flight

<<Can I send this to the list?>>
 
sure
 
<<Evidence? The size of lagosuchids etc.. I'm not speaking of *strict* insectivory (anteater-style) here, just the fact that today all small non-herbivores eat insects, and not of the size range of herrerasaurids.>>
 
I don't know how many insects you would need to eat to get enough solphures to be able to use it  to "build" modified scales,  but  I feel like something more specialized than a potentially, partially insectivorous diet by non strict incesctivorous animals should be needed.
 
However this is only speculation vs speculation since I  think nobody has tried to quantify this measure.( how much insects, given an individual quantity of solphures  for every single of them, would be needed)
 
<<You know, most or all of the above is true, and yet it works in today's dippers (Cinclus), as I have mentioned, who are passeriforms (songbirds; they are called "water blackbirds" in German) and have, count them, ONE adaptation to their lifestyle, they can close their nostrils with flaps of skin that are unlikely to fossilise. >>
 
Something to say on this:
-these animals don't live in sea enviroment, right?(I'm asking since i don't know exactly, but they seem to be something similar to an animal I know and are probably the same); They live and hunt in little mountain rivers hardly comparable to an open sea .
 
They evolved this behaviour after  they evolved the ability to fly,not before;  being able to do what these little water blackbirds do needs very probably the ability to flight to be already present.(unless they hunt in too shallow little rivers for which high speed of penetration is not needed).
 
<<I should have added (or have I? I think I have) that Ebel proposes that the stiff, feathered tail of Archaeopteryx was for steering underwater (changing directions laterally would have been possible by rotating the tail, he writes; pelicans use their remarkably stiff tail feathers for steering when they're diving).>>
 
I think it would be interesting to know  how lenght of tail an body dimensions  are somewhat related in some way regarding this use of the feathered, stiff tail.
 
 
<<Flying offers the advantage of being able to get to new fishing grounds fast and to look for fish from above, which tends to be easier.>>
 
This is an adaptation ( maybe, more precisely an exaptation if I've understood correctly the meaning of this word) of the already evolved ability to fly, not the selective pressure that led to it.
I think it's needed to distinguish these two things since they're really important.
 
<<Of course it must be tested. It's supposed to be science. >>
 
Right.
 
<<it doesn't sound extremely likely, but more likely than ground-up and trees-down >>
 
I assume you say this only based on personal feeling   more than some kind of experimental evidence.
Based on the same(personal feelings)-but i think with some more empirical bases- I'm for the ground-up theory .
 
 
I've received no attachments to your post and infact I was really asking to myself what Miss Kirkaldy was talking about; 
 
if you feel, you can send this one to the list too
(were you talking about sending only your response, to the list or my first letter too ?..it would be ok in both cases)
 
Bye
 
Filippo