"Sickle claw" potpourri (was Re: SVP Papers)

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

Jordan Mallon wrote:

> A large sagittal crests usually suggests large jaw muscles for powerful 
> biting.  If Deinonychus is now considered to have had a powerful bite, I 
> wonder how that might be incorporated with its supposed style of "kick-box" 
> killing?

Strong jaws accord well with the 'grappling' attack strategy suggested for 
_Deinonychus_.  The hands of this beastie had minimal grasping ability, 
except when used together (such as to encircle large prey).  If the 
forelimbs were used to grab onto prey, then the jaws and feet could be used 
to subdue or dispatch the prey.

Sebastian wrote:

> The true position of the claws is not minor in significance. It has deep 
> phylogenetic and functional implicances. For example, the change in 
> position of the Megaraptor claw, from the pes to the manus, was an 
> important part of the data that removed this taxon from Maniraptora to drop 
> it to the basal tetanuran bag! You will see it soon in the last 
> Ameghiniana.

I agree.  The presence/absence of a "sickle claw" has enormous functional 
significance, and AFAIK only eumaniraptorans have a second toe that is both 
hyperextensible and bears a sickle claw.

While on the topic of sickle-claws... The modern seriemas (Cariamidae; 
Neoaves incertae sedis) have an enlarged and highly curved talon on the 
inner toe.  Seriemas are long-legged predatory birds that spend most of 
their time on the ground (although they do roost in trees).  The sickle-claw 
is used in predation and intraspecific combat, but I've also read/heard that 
this talon is used as a climbing aid.  My question is: How?  Obviously 
seriemas do not climb vertical trunks.  So what does this special claw help 
them climb - and in what fashion?  The observation that this special 
"sickle-claw" of seriemas is used in climbing is mentioned in the Handbook 
of the Birds of the World (HBW), but I have been unable to track down the 
original reference (assuming there is one).




Tim

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