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




In response to Jamie's list of assumptions I wanted to point out a couple things:


2. Felids and falconids use their claws to grip, primarily, rather
than cut.
The bulk of the claw is used to pierce and hold prey, and cannot be used to
slice (given the lack of a cutting ventral edge). <<<


I did not refer to falconid claws in that context (or the quote), rather I specifically referred to "the cutting edge of raptorial bird beaks" because in fact the cutting edge does not work without the keratinous sheath. I did mention felid claws, specifically because 1) despite their lack of similar specializations cats routinely manage to or at least gash quite effectively, to the point of dissemboweling prey (as has been suggested for dromaeosaurs), and 2) their bony cores would not be able to do so in an experiment similar to the one Manning et al carried out with the Deinonychus claw core

I intentionally did not mention mention raptorial (avian raptors, that is) claws because they are specialized for puncturing and holding prey, and their resulting cross-section is nothing like the sickle-claws of deinonychosaurs. Allosaur manual claws have more in common cross-sectionally with the pedal claws of falcons and their kin.

3. Regardless of the ventral constriction of dromaeosaurid unguals,
the
unguals lack a sharpened edge. The conclusion that the keratin sheath should
follow and develop on the shape of the underlying ungual is likely, but to
exagerrate the shape is based on a previous assumption of function.<<<


That's my point, the claws are not merely laterally compressed, they are in fact forming an edge (at least in Deinonychus and Velociraptor), although not one that will cut through flesh without the sheath (and again, try shearing through meat with an eagle skull that lacks the ramphotheca). It's worth noting that felid and falconiform claws are very different from each other. While there's a decent bit of variation (especially with cheetahs) in general felid claws are more laterally compressed than falcon claws, so it's no suprise that felids more frequently use their claws to inflict slashing wounds.

Cheers,

Scott Hartman
Science Director
Wyoming Dinosaur Center
110 Carter Ranch Rd.
Thermopolis, WY 82443
(800) 455-3466 ext. 230
Cell: (307) 921-8333

www.skeletaldrawing.com