[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

RE: Campbell's even crazier than a MANIAC? (archeopteryx climbing)



Quoting Tim Williams <twilliams_alpha@hotmail.com>:

>> Sim Kining wrote:

> > An eagle's talons are highly specialized for predation, so are the claws of 
> > large cats, 
>> neither seem to have a problem climbing around or perching in trees. 

> Neither of these has claws *as* specialized as the sickle claw (and its
> supporting digit) of dromaeosaurids.  Not even seriemas (cariamas).

Indeed. Eagle and cat claws tend to have circular or ovoid cross sections (as 
do the claws of just 
about any climbing, perching or grasping creatures). The narrow blade-like 
sickle claws of the 
larger dromaeosaurs would seem to be ill-suited to standing up to twisting or 
sideways forces.

> Yeah sure, maybe the sickle-claw of dromaeosaurids was used for climbing,
> branch-grasping, etc.  But it clearly didn't evolve for this purpose.  It
> sounds like a counsel of despair to argue that the sickle-claw was an
> arboreal tool - especially when there's no elongated, reversed hallux on the
> other side of the foot.

Given that those retractable swivel-toes seem to have been designed 
intentionally to keep the 
sickle claws clear of the ground, I also doubt they were regularly driven into 
trees. Perhaps the 
smaller, less blade-like claws of Dromaeosaurus itself (or Tro-odon for that 
matter) may have 
been used as climbing aids on occasions, but animals like Velociraptor or 
Deinonychus probably 
preserved the claw tip as much as possible for use in hunting. It's best to 
climb with a sturdy hook, 
not a narrow blade.

It begs the question though; are the more 'advanced' dromaeosaurs with the 
blade-like toe claws 
decended from earlier climbing animals? Perhaps dromaeosaur ancestors had 
stouter, chunkier toe 
claws for climbing, and the lance-like toe claws of the larger and later 
dromasoesaurs were 
specialised forms - too specialised to continue being used as climbing aids. 

How do the toe claws of juvenile Velociraptors compare to those of the adults? 
If juvies have less 
blade-like toe claws, then maybe they were used as climbing aids in juveniles, 
but changed shape 
as they matured to the point that adults were no longer able to use them for 
climbing.

-- 
___________________________________________________________________

Dann Pigdon
GIS / Archaeologist              http://geo_cities.com/dannsdinosaurs
Melbourne, Australia             http://heretichides.soffiles.com
___________________________________________________________________