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

[dinoboygraphics@aol.com]

> > >  Do recall in the TV spot that the experimentalists using ONLY the 
bony cores of *Deinonychus* pdII-3s were unable to acheive a cutting 
action in soft
material, which is why the "crampon" idea has received more attention 
recently.<<<

Sure, but try to cut through flesh with the bony core of a felid 
claw...yet tigers regularly dissembowel ungulates, and even my cat can 
give a nasty gash to a careless stranger.  As the "crampon" spike gross 
morphology does not match with that of Archaeopteryx or deinonychosaur 
#2 pedal claws, it's a poor functional analog.

> > > Who says they had a cutting edge? Not all dromaeosaurid claws have 
a tomial
ridge on the ventral edge. In fact, only that of *Utahraptor* has this 
feature,
and that holotypic claw is crushed mediolaterally, exaggerating the 
degree to
which the claw seems narrowed. The sharpened ventral margin is an 
inferrence
that's been applied to them _because_ they were assumed to be cutting 
devices.<<<

Well wait here, "tomial" is the cutting edge itself (e.g. the cutting 
edge of raptorial bird beaks) and itself depends on the morphology of 
the keratinous sheath.  If you were to strip the ramphotheca from a 
falcon skull I doubt very much that it would tear through meat with the 
same prowess as the living animal does (with ramphotheca intact).  The 
#2 pedal claw morphology in Deinonychus and Velociraptor certainly 
constrict ventrally, leaving an inverted teardrop  shape that is very 
derived compared to the primitive condition (and indeed the condition 
of the other pedal claws) which are sub-triangular in crossection with 
the widest portion at the base.  Also, in the Thermopolis Specimen and 
in Chinese dromaeosaurs that preseve impressions of the keratinous 
sheath or the second there is more keratin on the ventral surface, so 
unless the sheath cross-sectional morphology differed radically from 
the bony core it the already narrowing claw would have to pinch out to 
an edge.


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


-----Original Message-----
From: Jaime A. Headden <qilongia@yahoo.com>
To: david.marjanovic@gmx.at
Cc: dinosaur@usc.edu
Sent: Sun, 7 Sep 2008 2:16 pm
Subject: Re: Campbell's even crazier than a MANIAC? (archeopteryx 
climbing)



David Marjanovic wrote:

<Don't crampons work side-to-side? Sickle claws worked top-down and 
probably had
a cutting edge. They were not round in cross-section.>

  Who says they had a cutting edge? Not all dromaeosaurid claws have a 
tomial
ridge on the ventral edge. In fact, only that of *Utahraptor* has this 
feature,
and that holotypic claw is crushed mediolaterally, exaggerating the 
degree to
which the claw seems narrowed. The sharpened ventral margin is an 
inferrence
that's been applied to them _because_ they were assumed to be cutting 
devices.

  Do recall in the TV spot that the experimentalists using ONLY the 
bony cores
of *Deinonychus* pdII-3s were unable to acheive a cutting action in 
soft
material, which is why the "crampon" idea has received more attention 
recently.

 Cheers,

Jaime A. Headden
http://bitestuff.blogspot.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)