RE: Claws on deinonychosaurs

[Ken.Carpenter@dmns.org]

With respect to Jamie, he forgets that the claw of the foot in the
vicinity of the throat is extended, the other toes curled back. That of
the other foot is not.  Thus, the claw was being engaged as a weapon.
With a sample size of one, we do not know whether  this was the normal
place of attack, just that in this instance it was. As Manning and I
have independently noted, the sickle-claw was used as a piercing weapon,
not as a slicing-dicing Ginzu knife. 

Kenneth Carpenter, Ph.D.
Curator of Lower Vertebrate Paleontology/
Chief Preparator
Department of Earth Sciences
Denver Museum of Nature & Science
2001 Colorado Blvd.
Denver, CO 80205
 
Phone: 303-370-6392
Fax: 303-331-6492
************************************************************
for PDFs of some of my publications, as well as information of the Cedar
Mountain Project: 
https://scientists.dmns.org/sites/kencarpenter/default.aspx

-----Original Message-----
From: Jaime A. Headden [mailto:qilongia@yahoo.com] 
Sent: Tuesday, November 01, 2005 3:42 PM
To: dinosaur@usc.edu
Cc: Ken Carpenter
Subject: RE: Claws on deinonychosaurs

Ken Carpenter (Ken.Carpenter@dmns.org) wrote:

<Argh! Somebody please explain to me (not done in the original
description by
Maxwell and Ostrom) how multiple predators/scavengers on a carcass
suddenly
fall over dead! (and please don't say volcanic ash because they aren't
buried
in ash, nor is there evidence for poison gas, blah, blah). The specimens
in
question (Deinonychus and Tenontosaurus) are mostly disarticulated so
their
association may be incidental). Some facts, please, rather than
unsubstantiated
speculation (this is NOT a criticism directed at Mickey, but my
colleagues who
make such statements).>

  I am of all things curious aboute more than the Maxwell and Ostrom
association of a *Tenontosaurus* with the remains of at least three
different
*Deinonychus* corpses, given the preserved tails of other fragments.
Such an
assemblage indicates they were deposited together, but does not give us
data on
how they died. We infer they died together because of the amount of shed
teeth
associated with *Tenontosaurus* skeletons in the Cloverly, which Ostrom
(1969)
mentioned. Such teeth were also associated with the holotype of
*Microvenator*,
AMNH 3041, but the number is so high I cannot imagine a single animal
loosing
over 20 teeth on an prey item 1/24th it's own size. It has also not been
addressed that the corpses of *Tenontosaurus* were dead prior to
*Deinonychus*
scavenging, at least in print, largely due to the effects of romantic,
wolfish
hunters taking on a large prey animal, lion vs wildebeats and bobcats vs
moose!

and in a later email:

<The question I asked has far greater ramifications than just the
Deinonychus-Tenontosaurus assemblage (I thought someone would pick that
up). It
applies to all mixed multiple theropod-prey assemblages (e.g.,
Daspletosaurus-hadrosaur bone bed, etc.).>

  In truth, unless there was incontrovertible evidence that predation on
a
corpse occurs, the null hypothesis is that both skeletons were deposited
at the
same time, without any allusion to what they may or may not have been
doing to
one another (queue cheesy 70s porn music).

  But getting back to sickle claw useage, Ken wrote in Carpenter (1998)
[Carpenter, K. 1998. Evidence of predatory behavior by carnivorous
dinosaurs.
_GAIA_ 15:135-144.] that "[t]he fighting pair provides the best evidence
for
the function of the sickle claw in dromaeosaurid theropods. This
function is
not the same as that suggested by OSTROM, (1969) for another
dromaeosaurid,
*Deinonychus*. Ostrom proposed that Deinonychus "caught and held its
prey in
its fore hands and disemboweled it with the large pedal talon" (OSTROM
1969:
143). However, in the *Velociraptor*, the sickle claw is extended in the
vicinity of the throat (Fig. 1A). This evidence suggests that the claw
was not
used to disembowel the prey, but that it may have been used to pierce
the
jugular vein, carotid artery, or trachea. These are areas that many
extant
mammalian carnivores attack in prey." (pg. 138)

  Unfortunately, the evidence for the position of the foot, while valid,
requires that the association of the skeletons in question, in the
Fighting
Dinosaurs pair, to be natural and unaffected by death postures or
deposition
conditions (the accumulation of the sandslide, for example). Indeed, the
positions of both feet in the GIN 100/25 *Velociraptor*, are tucked up
into the
same position, with the lower of the two in the same position as the one
positioned at the *Protoceratops*' throat. The body is curled up, the
tail and
head pulled back, the arms up and forward. My cat makes the same
position as a
defensive posture, and I do not recall ever seeing a predator engage
prey from
below, not that I am sure it's not possible, but that the likelihood
seems a
bit far to reach when the sides and rear seem more viable attack
positions.
When cats turn into a defensive posture, they protect the vulnerable
back,
sides, and neck; they also while exposing the ventral side, bring into
play ALL
of their claws and teeth, and while using the forelimbs to grip and
pull, can
use the rear to "catscratch" and if neccessary inflict defensive bites
on what
they are holding, hoping (as my cat does) that it can be as annoying as
possible to force the attacker to retreat. On top of this, you have an
animal
the size of a *Protoceratops* [which it so coincidentally appears to
be], which
likely weighed 2-3 times as much as *Velociraptor*, nearly sitting on
TOP of
the *Velociraptor*.

  It seems at least as likely to me that the *Protoceratops* forced the
*Velociraptor* into a defensive posture, resulting in the reflexive
retraction
of the head, the "curled" body with the hindlimbs drawn up and onto the
aggressor's body while the arms tried to grip the head as well. In the
process,
the *Protoceratops* has grabbed hold of the *Velociraptor*'s forelimb,
and has
broken the radius where the upper jaw has connected with the arm. Does
this
position not beg the question of why an aggressive predator has taken
the risk
of sliding beneath a *Protoceratops* to go after just the throat?
Perhaps it
may seem more viable to attack the back and sides. Despite it's rarity,
when
lions do go after porcupine, they learn that the only viable attack
direction
is to find a way to get the animal exposed onto it's back, whereas
otherwise
the animal is protected from nearly all directions. Similarly, the proto
head
shield protects the neck from attack from above and to the sides, but
this does
not mean the underside, when the proto needs but to sit on the predator,
to
effectively disable it. A horse landing on a man has a similar effect in
making
much of an attack horrendously pyrrhic.

  Cheers,

Jaime A. Headden

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


        
                
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