Alvarezsaur spurs (was Re: dino-lice)

[Dann Pigdon <dannj@alphalink.com.au>]

On Wed, Apr 20th, 2011 at 12:17 PM, Tim Williams <tijawi@gmail.com> wrote:

> I have no doubt that alvarezsaurids used their truncated, monodactyl
> forelimbs for *something* - and as with the tyrannosaurids, it was
> probably a trophic function.  But unlike David M., I associate
> forelimb truncation in alvarezsaurids with a lack of day-to-day usage,
> rather than being an optimization for digging.

The problem I have with envisaging them as specialised diggers is that anything 
within reach of 
those stumpy forelimbs would seem to have been also out of sight. Not being 
able to see what you 
are digging into would appear to be a major disadvantage. Having such long legs 
would also seem 
to require them to be in some sort of prone position in order to dig.

Perhaps they were useful for scraping out nest hollows while the animal was 
lying prone, done 
mostly by feel rather than sight. Otherwise they'd have been quite inconvenient 
excavation tools. 
Neither would they seem to have been much good for defense, since any predator 
close enough to 
be in range of the forelimbs had probably already bitten into the head or neck.

They do remind me somewhat of platypus spurs though, which are used almost 
exclusively in 
intraspecific combat (platypus don't produce much, if any, venom outside of the 
breeding season, 
so the spurs aren't much use as a general year-round defense against predators).


-- 
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Dann Pigdon
Spatial Data Analyst               Australian Dinosaurs
Melbourne, Australia               http://home.alphalink.com.au/~dannj
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