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I've been busy defending truth and the American way from the forces of
anti-scientific evil of late, to the point of being the focus of global
op-eds and appearing on FOX (you know, they really are not fair and balanced,
but they did send a car to drive me all the way to their studio in DC which
was really cool) News. I could pretend it's a heavy burden to bear, but hey
it's great fun. Dealing with the press and media helped keep me away from SVP,
but the discussion on dromaeosaur predation warrants attention.
As Therrien et al. note in the brand new The Carnivorous Dinosaurs, the
extremely narrow snouted, delicately constructed, rather small toothed skulls
velociraptorine dromaeosaurs are not strong predatory devices compared to the
much stouter, broader snouted, bigger toothed skull of Dromaeosaurus. Having
rerestored the skull of Deinonychus based on nearly complete material I was not
impressed, despite its very large size, with its killing potential compared to
those of other theropods. This suggests that velociraptorines did not
emphasize the head as a killing device. Certainly the long, big clawed hands
important predatory devices, but the arms and slender fingers appear to lack
power needed to deliver killing blows. That's probably true of all theropods.
What is especially well developed is the big sickle claw, which is powered by
strongest organ on the body, the entire hindleg.
I used to have a cat. One nice spring day while chasing another cat - it's a
long story - she decided it was finally time to assert dominance over the tall
biped that fed her and took a good swipe at my leg, leaving long bleeding
claw marks. This with four wee little claws at the end of a her little arm.
Now cat claws are sharply curved and sharp pointed, and lack a sharp cutting
edge on the ventral rim. The claws of the big cats can ribbon long stretches
of flesh - I've seen horrendous wounds left by big cat claws on the flanks and
legs of ungulates - even though the claws are modest in size, and the force
of an arm or leg is spread among out among multiple claws. The sickle claws of
velociraptorines were much larger, and the entire force of the leg was
concentrated on the one claw. There is every reason to conclude that a
velociraptorine could produce a much more severe wound with its two sickle
claws than could
a cat of the same mass.
As others have noted, the target used by the researchers in the BBC project
do not appear particularly realistic - the failure to first test their machine
by replicating the wounding action of cassowary saber claws is a major failing
(albeit common to paleontological studies) - and a crude mechanical model may
not be able to deliver a wounding stroke with the sophisticated application
of force that maximizes the damage that can be achieved by a well experienced
living organism. The thin superficial belly tissues are subject to developing
hernias without even being wounded, so it is difficult to see why penatrating
and then ripping at them with one or two hook claws powered by the legs could
not slit or tear them open. Whether sickle claws would rip or tear would seem
to depend in part on the orientation of the wounding stroke relative to the
grain of the muscles fibers and other tissues. If the stroke is with the grain
then there would be a slicing effect. If perpendicular to the grain a tear
should result. Another vulnerable area is the neck where veins and the trachea
near the surface.
As others have noted the fighting Velociraptor and Protoceratops are highly
informative. The hands were indded being used to hold onto but not kill the
prey. If velociraptorines used the head to kill then the Velociraptor should
been biting the Protoceratopds, instead its head is pulled well away from -
but is looking at - the herbivore. The predator is using its cranium to see
what it's doing, not to attack the supposed victim. It is the sickle claws that
are attempting to dispatch the Protoceratops, apparently by slashing at the
veins or trachea.
It is interesting that we do not know what kind of sickle claw Dromaeosaurus
actually has, the large pedal claws that were assigned to the genus may well
belong to velociraptorines.
Of course sickle claws probably served multiple purposes. Cats use their
claws to hold and wound prey, and and to climb both trees and prey. No reason
sickle-claws couldn't use them to climb trees or herbivores before using the
claws to kill their hapless victims. I discuss all that in Dinosaurs of the
Air. It is hard to see how or why velociraptorines would use the big, sharp,
powerful sickle claws merely to hold onto prey while they used their slender
to try to kill it. That wouldn't be smart.