Re: NEW NEORNITHINE & PTEROSAUR STUFF

["Tim Williams" <tijawi@hotmail.com>]

Jaime Headden wrote:

>  I have a question: to what use
> can such claws be of, and be prevalent. They are present among many extant 
> birds, including the
> hoatzin ... but for what function can they serve to have _not_ been 
> vestigialized in all birds? It
> is obvious that hoatzins use them for locomotion, but it is not clear to 
> what use they serve in
> other taxa. So it is a matter of an enigma: what _would_ such small claws 
> serve? And yes, we know
> _all_ about scampering young hoatzins...


Ah, but do you know about adult hoatzins...

Many adult hoatzins retain the wing-claws of juveniles, but they are buried 
in callus and presumably useless.  Similarly, the claws of these early 
Cenozoic neornithines might have been vestigial and utterly nonfunctional.

Another suggestion for the manual claws of _Tynskya_ and _Fluvioviridornis_ 
is that they were used in intraspecific combat - like the metacarpal spurs 
of many modern birds.  The presence of wing-spurs has arisen several times 
in neornithine birds (screamers, spur-winged geese, jacanas, sheathbills, 
spur-winged plovers).  They protrude from the bend in the wing, and are used 
as quite formidable weapons (always on the ground or water, and never in the 
air, AFAIK).  There are even reports of spurs being found embedded in the 
chests of screamers (anhimas), so they are detachable - and apparently used 
to wack a rival with considerable force.

I would guess that grasping abilities are ruled out for any neornithine, 
since the mobility of the manus and carpus would be limited by 
coossification within and between these elements.



Tim


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