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Re: Alvarezsaur spurs (was Re: dino-lice)



On 20 April 2011 20:51, Jason Brougham <jaseb@amnh.org> wrote:
>
>
> Thanks, man.
>
> You can see my reconstructions of maniraptorans using their wings for
> temperature regulation at:
>
> www.jasonbrougham.com
>
> go to illustrations/ecological and reproductive reconstructions. I got the
> idea from Hopp and Orsen (2004).
>
>
>

Good stuff! It's a pity ideas (like yours) that link forearm mechanics
(or any biomechanics) to display are really difficult to test. The
conditions for a successful display are a lot harder to constrain than
for successful locomotion. I mean, other than assuming
more/faster/more complex motion is somehow better, there doesn't seem
to be a lot to go on.

>> On 20 April 2011 14:54, Jason Brougham <jaseb@amnh.org> wrote:
>>>
>>> My favorite interpretation of alvarezsaur pectoral limbs has always been
>>> that they supported fans of long feathers or ribbon- like keratinous
>>> straps (like ETFs in scansoriopterygids) for display. In figure 18 of
>>> the
>>> Patagonykus monograph (Novas, F. E. 1997. Anatomy of Patagonykus puertai
>>> (Theropoda, Avialae, Alvarezsauridae), from the Late Cretaceous of
>>> Patagonia. Journal of Vertebrate Paleontology 17(1); 137-166.) there
>>> appears to be a lateral groove on Ph I 1 of the right manus, and the
>>> groove is over 40mm long. This feature, possibly combined with the ulna,
>>> may have served well in anchoring follicles.
>>>
>>> One virtue of my hypothesis is that it explains why flapping musculature
>>> may have hypertropied while the hand was reduced in both size and
>>> function. The shorter arm should have been able to flap or even vibrate
>>> at
>>> much higher frequencies and with some force. I picture the feather fan
>>> trembling not unlike the rectrical fan of the peacock. Another virtue of
>>> this hypothesis is that it is consistent with archosaur biology in that
>>> birds have arrived at a diversity of bizarre morphological adaptations
>>> for
>>> display, while none that I know of have been highly modified for
>>> digging.
>>>
>>> The problems include that the arm morphology doesn't really suggest a
>>> way
>>> to fold such a fan for fast running, and that the hands are not clearly
>>> modified for strong feather attachment with lateral flanges. But it is
>>> possible that the follicles lay in a soft tissue "remigial bulb".
>>>
>>>
>> Hey - this sounds neat. Fits pretty with Ostrich wing retention
>> (mainly for display) as well. I've heard (lemme dig around see if I
>> can find a paper) that Ostriches also use their wings for temperature
>> control as well. Could extend to other taxa as well? I mean, If you
>> believe that most Coelurosaurs have 'wings' to some degree, then
>> display gives you a good reason for maintaining forelimbs even if
>> they're%2