David Marjanovic wrote:
that immobility is a great thing for such a predator, as this
makes it
much more difficult for prey to escape, relatively much easier --
no
muscular effort is required -- for the predator to hold it.
*** Not to belabor the issue, Ostrom '69 sums it up as follows:
"The manus of Deinonychus was a highly perfected and powerful grasping
structure quite unlike that of any other adequately known theropod. The
most important features confirming this conclusion are the long and stout
first and second digits with their large trenchant and strongly recurved
claws, the slender abductable third digit with its unique restrictive joints,
the very large flexor tubercles on all unguals, the highly perfected carpus
that provided extensive and precise abduction and supination of the hand, the
unusual length of of all forelimb components and great size of the
deltopectoral crest and internal tuberosity."
***He also makes mention of the strong collateral ligament pits that
suggest strength between phalanges and therefore digits as a whole. As a
related aside, I was at the library today looking at a book on mammalian
predators which included a photograph of a leopard in a tree with one forelimb
outstretched and hanging from the tip of a single claw was an entire carcass
of a baboon it had captured earlier on. Transpose that sort of digit
strength onto a Deinonychus.
Can somebody please tell me why they think this
is so? But first, try these simple experiments. You'll need a pair of hands
and an angry cat. Holding your fingers rigid, and your hands facing inward,
try to grip the struggling cat. After applying ointment and plasters,
try again, this time with your full range of mobility. Which works
better?
*** Now, lets modify your first experiment. Lets
implant nasty recurved claws with large flexor tubercles (indicating
attachment to strong digit flexor muscles in my forearms) into the ends of my
fingers. Let's lock together my first two metacarpals, give me enlarged
deltopectoral crests which will be attached to significantly strong pectorals
and other adducting chest / shoulder musculature. For good measure throw
in a sharp recurved oversized second pedal ungual and a set of small but sharp
serious teeth, a respectable appetite. . . Suddenly your struggling cat has
been reduced to "puppy chow" in less time than it took you to read the words
"puppy chow".
Secondly, partially bend your right
index finger. Now press it against your left hand. Move your left hand
about a bit. You'll notice that the flexibility of your digit improves both
contact and safety. If you try it again, this time with your finger
straightened and bent back till it is immobile, not only is it less use, it is
also in serious danger of getting broken!
*** From Ostrom's description and what I
understand about Alan Gishlick's paper ( I don't have a copy but have read
references to it), although the digits are frozen or restricted in respect to
some interphalangeal articulations, their is still flexion between
metacarpals and digits and digits to unguals. This then, does not
parallel your example of imposed digit hyper extension above. Even if
their was complete immobility of the hand beyond the wrist (consider
Captain Hook for a moment with a snap on, triple bladed, gardening
implement instead of his standard steely single claw) and a penchant for
performing bust improvement exercises. When Freddie Kruger or Deinonychus
are looking for a "hug", it's time to leave the party!
Cheers,
Mike
Skrepnick