RE: Third claw for climbing was Re: Pro(to)avis

[Tim Williams <twilliams_alpha@hotmail.com>]

Jerzy Dyczkowski wrote:

> Just a question: how helpful could be enlarged third claws of some 
> theropods during climbing tree trunks?

If you mean the enlarged FOOT claw, then this is on the second toe.  The 
idea that this claw may have been used for trunk-climbing (and perhaps 
originally evolved for this purpose) has come up before.  (Did Sankar 
Chatterjee suggest this?)

I've heard that seriemas (modern predatory birds) have an enlarged claw on 
their inner toes, and it it is used in both predation and climbing.  Though 
I've not been able to find an original reference which says *how* and *why* 
seriemas use these claws for climbing - after all, seriemas are perfectly 
good fliers, and they hunt on the ground, so why should they need to climb?  
I also believe that some phorusrhacoids had an enlarged inner claw (e.g., 
_Psilopterus_).  In these birds, the claw is enlarged, but not 
hyperextensible as it is in deinonychosaurs.

> It occured to me that some maniraptorians with enlarged claw on legs were 
> rather slim animals, not build for wrestling big prey.

The enlarged sickle-claw on the foot could perhaps have also been used to 
dispatch small prey, that was pinned to the ground with the entire foot.  By 
"small prey", I mean lizards, frogs, juveniles of other dinosaurs, various 
invertebrates...

Cheers

Tim