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Re: Claw function in Deinonychus



Excellent points Richard. My own take is rather
simple. Why have the thing if it's so unnecessary? I
don't think such a weapon would develop if it wasn't a
very useful and necessary tool. And it remained on
every dromaeosaur and Troodont for as long as they
remain in the fossil record and I'm guessing that all
the various 'raptors' were taking on various prey and
killing styles. Mostly smaller but sometimes probably
bigger prey when possible or necessary.

It's the simple answer for me. Hey, look at that
spring loaded weapon. What would that be good for? Oh,
killing and maiming before some dangerous thing can
injure you with it's own weapons. 

And we have a Velociraptor gutting a Protoceratops.
What more do they need? 

ADS

--- Richard and Jo Cowen <cowen@blueoakfarm.com>
wrote:

> Manning, P. L., et al. 2005. Dinosaur killer claws
> or climbing  
> crampons? Biology Letters Online Publishing, October
> 11, 2005
> 
> Abstract (freely available online, I believe):
> Dromaeosaurid theropod  
> dinosaurs have a strongly recurved, hypertrophied
> and hyperextensible  
> ungual claw on pedal digit II. This feature is
> usually suggested to  
> have functioned as a device for disembowelling
> herbivorous dinosaurs  
> during predation. However, modelling of
> dromaeosaurid hindlimb  
> function using a robotic model and comparison of
> pedal ungual  
> morphology with extant analogue taxa both indicate
> that this  
> distinctive claw did not function as a slashing
> weapon, but may have  
> acted as an aid to prey capture.
> 
> News story:
> http://news.bbc.co.uk/1/hi/sci/tech/4332272.stm
> BBC News OnLine
> 
> The full paper in Biology Letters is not available
> unless your  
> institution has a subscription. Here are some points
> from it.
> 
> First of all, you have to know that this project was
> done in  
> connection with a TV show for the BBC (The Truth
> About Killer  
> Dinosaurs). Second, a 5-author paper that had
> multiple reviewers and  
> editors and proof readers shouldn?t be quoting
> ?speeds? in meters per  
> second squared: those units denote acceleration. It
> makes you wonder.
> 
> They designed a hydraulic limb based on the
> structure of Velociraptor  
> and Deinonychus. The leg bones were mimicked by
> steel rods,  
> controlled by hydraulics; and the hyperextension of
> the big claw was  
> effected by a control cable. The claw movements were
> reconstructed  
> mostly from the beautifully preserved foot of
> Deinonychus. The model  
> was based on a body mass of 40 kg for the animal.
> 
> The claw was made from an aluminum core with a
> sheath of Kevlar and  
> carbon fiber set in epoxy resin, which was sharpened
> appropriately.  
> Then they banged the claw into a pig carcass mounted
> on a frame at  
> speeds of 2 m ?per sec2? and 11 m/sec2. Assuming
> these are real  
> speeds misquoted, they represent roughly 4 mph and
> 20 mph.
> 
> The claw did not penetrate far into the pig carcass,
> so the authors  
> conclude it didn?t cause slashing wounds. Therefore,
> they suggest,  
> the claws were used like crampons to climb up the
> flanks of their  
> prey until they could bite them!!!
> 
> I really have problems with this, though I?m not in
> a position to  
> solve those problems.
> 
> We don?t know what the ?pig carcass? really was. In
> the photos in the  
> paper it looks like a clean, cold, piece of pork
> from the local  
> village butcher (it has one of those violet stamps
> on it). It?s  
> mounted as a solid lump on a metal frame: no ?give?
> at all as there  
> would be in a living animal. No wonder the claw
> didn?t penetrate  
> much. Let?s go back to the abstract: if the claw is
> ?usually  
> suggested to have functioned as a device for
> disembowelling?, and the  
> device just banged the claw into a cold cleaned
> carcass, then they  
> didn?t test the disembowelling hypothesis at all.
> What you need is a  
> claw applied appropriately to the guts of a warm
> animal. More on this  
> below.
> 
> We don?t know just how the claw impacted the meat.
> If it hit the meat  
> more or less directly, of course it would try to
> penetrate, even if  
> it didn?t get very far. If it hit the meat in a mode
> in which the  
> claw was moving to close just as it hit the meat,
> then the claw  
> motion would have been dominantly slashing on
> impact, and would have  
> been much more likely to tear the flesh in a cutting
> action. The  
> authors don?t say, but since they are so keen to
> tell us the ?speed?  
> of the claw, that means to me that the claw?s motion
> wasn?t  
> dominantly slashing. The picture gives the same
> impression, though  
> it?s difficult to tell just how the claw was moving
> on impact. So  
> again, the hypothesis was not tested.
> 
> Apart from anything else, I don?t like the crampon
> hypothesis.  
> There?s nothing potentially lethal to bite even if
> you succeed in  
> getting up on to the flanks of a big animal.
> 
> The other thing is that this whole ?test? and then
> the subsequent  
> inferences are predicated on the supposition that
> the raptors were  
> attacking prey much larger than they were: a roughly
> 90 pound  
> predator (a largish dog) attacking 500 to 1000
> pounds of pig. This  
> vision, I suppose, derives from brainwashing by the
> Bakker images.
> 
> My image is that it?s much more likely that the
> raptors were taking  
> on prey roughly their own size, or perhaps smaller.
> They?d knock them  
> down then disembowel them with the foot claw, before
> or after tearing  
> out their throats with their teeth. So any
> experiment would be better  
> performed on a complete, warm, wriggling Bambi, with
> its belly skin  
> stretched by muscular exertion rather than being
> relaxed in death.  
> I?m not advocating this, of course, just making a
> logical point.
> 
> But wait: there are two sets of people who get close
> to that  
> activity. One consists of surgeons, whether they
> work on humans or  
> animals; and the other consists of hunters as they
> gralloch their  
> prey. I?m none of the above, so I?d welcome
> feedback.
> By the way, I'm putting this blurb on my History of
> Life website at
>
http://www.geology.ucdavis.edu/~cowen/HistoryofLife/slashingclaw.html
> 
> There are differences in technique, however, that
> have to be part of  
> the assessment. All the above are concerned to cause
> minimal damage  
> to the creature, the first because they?re trying to
> save its life,  
> and the second because they want a clean gralloch,
> without puncturing  
> the rumen, for example (pictures and instructions at
> http://wireviz.tripod.com/id3.html
> 
> But if you?re a predator, the more damage you cause,
> the better, so  
> perhaps a raptor-type claw is a good thing. At least
> one deer- 
> cleaning knife has a ?gut-hook? on it:
> http://www.deer-uk.com/Skinner.gif
> 
> Whatever deinonychines were doing, it was unique.
> But some  
> interpretations seem to me to be better than others.
> 
> Cheers
> 
> Richard Cowen
> rcowen@ucdavis.edu

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