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Re: Aquatic Origin of birds (was Aquatic spinosaurs (was Size of *Neoceratodus africanus*))



I think it was proposed, although I do not remember who, but I think
it is on Gregory Paul's 2002 book Dinosaurs of the Air. I think
Chatterjee (1997) also hypothesized proavians parachuting to fall into
water bodies and swim thereafter.

A problem with this aquatic phase hypothesis is that there is not much
evidence from the habits of the most basal lineages of extant birds
suggesting primitive aquatic habits. For example, I do not know of
aquatic paleognaths or galliforms, and even Anseriformes have a basal
split with one non-swimming branch (Anhimidae).

All this on basal Neornithes may be of little significance to oppose
to the hypothesis, but think that except for Hesperornis, there are
few evidences of aquatic habits in the more basal Avialae, and even
less phylogenetic reconstructions which lead to hypothesize this habit
is ancestral (I mean, if it was present in some hypothesized ancestor
of Avialae).

It also seems weird a flipper so long and with such movable
articulations, such as the avian wing. Although some phalacrocoracids
seem to use them as propellers, helping the feet.

2009/5/3 Erik Boehm <erikboehm07@yahoo.com>:
>
> Hmm.... Webbed theropod feet...
>
> That gave me an idea
>
> Many bird feet are webbed today.
> Many birds use their wings as flippers...
> Pterosaur wings were initially thought to be flippers...
> Many birds use their wings to both fly and swim...
>
> With all the discussion about WAIR, trees down/ground up flight, display, 
> etc....
>
> Has anyone suggested bird-like feathers + wings evolved first as flippers?
>
> I'm imagining some little pre-maniraptor Coelosaur swimming around with 
> feathered arm-flippers?
> Possibly evolving flight capacity in a way vaguely reminiscent of a flying 
> fish?
> Maybe very early takeoffs weren't done by running/leaping from the ground, 
> but rather from the water's surface like a loon?
>
> Could the early long tails with feathers in a horizontal plane conceivably 
> function like a beaver's tail? (Would extensive modification be needed to get 
> a therepod tail to flex up and down with enough force to propel it through 
> the water?) -I'd think it more likely to have a side-side motion if it were 
> for aquatic propulsion, but that doesn't rule out a semi-aquatic origin of 
> birds - they may have only used their flipper wings, and the broad feathering 
> of the tail evolves later for flight?
>
> Could small swimming/aquatic dinosaurs have lead to small flying/volant 
> dinosaurs?
>
> I think small aquatic dino-birds might not fossilize too well, and wouldn't 
> leave much evidence..
>
> Has this been suggested before?
>
>
> --- On Sun, 5/3/09, Dann Pigdon <dannj@alphalink.com.au> wrote:
>
>> From: Dann Pigdon <dannj@alphalink.com.au>
>> Subject: RE: Aquatic spinosaurs (was Size of *Neoceratodus africanus*)
>> To: dinosaur@usc.edu
>> Date: Sunday, May 3, 2009, 3:57 PM
>> Quoting Christophe Hendrickx <nekarius@hotmail.com>:
>>
>> > We now have the certainty there were semi-aquatic
>> dinosaurs, spending mostly their time into
>> > water, as crocodiles and turtles do
>> > (http://spinosauridae.fr.gd/Actualit-e2--des-Spinosauridae.htm,
>> see the abstract "Were some
>> > dinosaurs aquatic?").
>> > I know it won't be surprising for some of you but we
>> have to admit spinosaurids are usually seen
>> > as terrestrial animals and this was a matter of debate
>> recently
>> > (http://scienceblogs.com/tetrapodzoology/2009/02/month_in_dinosaurs_part_i.php).
>>
>> I recall a story many years ago of a webbed theropod track
>> having been found somewhere along
>> the coast of Western Australia. I'm sure I've got something
>> at home about it.
>>
>> Given the presence of spinosaurs in Africa and South
>> America, I wouldn't be surprised if they were
>> present in Australia as well.
>>
>> --
>> ___________________________________________________________________
>>
>> Dann Pigdon
>> GIS / Archaeologist
>>     http://dannsdinosaurs.dyn-o-saur.com
>> Melbourne, Australia
>>    http://heretichides.game-host.org
>> ___________________________________________________________________
>>
>>
>>
>>
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