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Re: FLYING-->FLIGHTLESS-->FLYING



--Original Message-- From: darren.naish@port.ac.uk : Tuesday, January 19,
1999 06:06 PM



>Quizzed by Tom Holtz, John Jackson writes...
>
>> Modern insects and birds are not a good analogy for this reason:
>> early flightless dino/birds went from one form to another and then
>> back to the earlier one:
>>    flightless -> flying -> flightless
>
>> modern flightless birds and insects effectively just do this:
>>    flying -> flightless
>
>How do you know this? There are numerous extant clades with closely
>related volant and non-volant taxa, and even SPECIES where some
>inviduals are volant and others are not. It is entirely possible,
>theoretically of course, for some extant volant taxa to have had a
>non-volant ancestor. Modern insects and birds are therefore entirely
>appropriate analogues for Jurassic-Cretaceous theropods.

Can you name one convincing example of a bird that has lost flight for say
10,000 years or more and then regained it?

I'm not talking about things like turkeys and bustards that slip in and out
of flightlessness on an individual basis, but lines where the physical
characteristics of flight were completely absent both before and after, such
as _Ornitholestes_ or _Sinosauropteryx_, and
_Ornithomimus_/_Troodon_/_Deinonychus_.

I declared in my first few weeks on the list the principle that insects are
not a good analogy for theropods.


>
>"The essence of science is that theories and models must be tested,
>rigorously" (Shipman 1998)

Is that a theory?  Has it been tested?  What if you could prove by testing,
the theory that theories didn't need to be tested?


JJ