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Re: Dino reputation 'is exaggerated'



Now let me see if I get this straight (hey, I can dream, can't I?) -- we would like some idea of the morphology of the exterior keratin of a dromaeosaur's #2 terminal pedal ungual_ in order to assess its function in seizing and/or dispatching prey (the subject of Phil Manning's recent study), and now it appears that _Rahonavis_, which has preserved keratin on said ungual, is actually a dromaeosaur.

From an osteological standpoint, how do the #2 terminal pedal unguals of
these taxa compare? Would it be reasonable to assume that _Velociraptor_ had a similar keratin morphology on this claw? If it appears that the #2 pedal claws of these taxa share sufficient morphological verisimilitude, does the pneumatic action _Velociraptor_ model capture the appropriate claw morphology? If not, how might a claw that is structurally similar to that of _Rahonavis_ function differently at the business end of a terrestrial dromaeosaur's foot? How might the use of this digit differ in a small flying _Rahonavis_ vs. _Velociraptor_ (and, by extension, how would _Deinonychus_ or _Utahraptor_ utilize their respective claws)?

I don't mean to diminish the work of Phil Manning, but rather to understand how _Rahonavis_ being a dromaeosaur would complement this analysis if indeed it would.

And no, I don't expect definitive answers on all of the above, which is why I asked questions rather than proposing conclusions, and put the "ifs" in place. I will defer to those who know more about such things than me.

Thanks in advance for any assistance.
--------
"Dino Guy" Ralph W. Miller III
Docent at the California Academy of Sciences
proud member of the Society of Vertebrate Paleontology
----- Original Message ----- From: "Michael Habib" <mhabib5@jhmi.edu>
To: <edels@msn.com>
Cc: <dinosaur@usc.edu>
Sent: Wednesday, October 12, 2005 12:00 PM
Subject: Re: Dino reputation 'is exaggerated'



Not that the "terror factor" has any real scientific importance or merit, but personally I don't find the prospect of being inescapably hooked into and gnawed to death much less worrisome than being kicked and hacked. Just a personal thought.

More to the point, does anyone know the specifics of the robotic arm utilized in the study? Their results could be right on target, but it could also be that the arm had too much power in initial strike and too little in pull.

--Mike Habib


On Wednesday, October 12, 2005, at 12:08 PM, Allan Edels wrote:

From the BBC:

http://news.bbc.co.uk/1/hi/sci/tech/4332272.stm


Text follows: ==================================================== Dino reputation 'is exaggerated'

The dimensions of the hydraulic limb reflected what is known from the fossil record

The _Velociraptor_ dinosaur made famous by the Hollywood movie Jurassic Park may not have been quite the super-efficient killer we all thought.
Like other dinos in its family, it had a distinctive sickle-shaped claw on the second toe which many have assumed was employed to disembowel victims.


But tests on a mechanical arm suggest this fearsome-looking appendage was probably used just to hang on to prey.

UK scientists report their experiments in the journal Biology Letters.

"This dispels the myth in place for some 40 years that this was a disembowelling claw - this is not the case," says Dr Phil Manning, from the Manchester Museum, University of Manchester.

"I'm saying that the primary function of this claw was to hold on to the prey, effectively like a climber's crampon," the curator of palaeontology told the BBC News website.

_Velociraptor_ belonged to the Dromaeosauridae, a family of small to medium-sized, lightly built and fast-running dinosaurs from the Cretaceous Period (146 million to 65 million years ago) who appear from the fossil record to have been very effective predators.

There is even evidence some, such as _Deinonychus_, hunted in packs.

They all possessed a large, curved claw on their big toes that could rotate through an arc in excess of 200 degrees.

By kicking and slashing, it has been widely thought these creatures could quickly open up their unfortunate victims, either killing them outright or making them bleed so profusely death followed very > quickly.

Dr Manning and his team tested the reputation on a robotic arm fitted with a life-like Dromaeosaur claw. The set-up was based on detailed fossil measurements.

The mechanical limb mimicked the sort of kick that might have come from a 2m-long, 40kg _Velociraptor_. The Kevlar and carbon-fibre-coated aluminium claw was thrust into the flesh from pig and crocodile carcasses.

Instead of producing the expected slashing wounds, the robotic impacts created only small, rounded punctures.

What is more, the way the skin tissue bunched under the impacts prevented the claw from withdrawing easily.

The punctures had a depth of about 30-40mm.

"It seems highly unlikely that wounds of this depth would have posed a danger to the vital organs of a large herbivorous dinosaur, though they would obviously be fatal to small prey," the team writes in Biology Letters.

Dr Manning does not want people to think less of _Velociraptor_ or _Deinonychus_ because of the research.

Its killing efficiency may not have matched their Hollywood image but the creatures would still have presented a terrifying prospect.

"It's effectively like a fatal embrace," he told the BBC News website.

"These claws were used to hook into the flanks of prey larger than them so the jaws could do the despatching.

"Imagine the scene: it's the Lower Cretaceous, and Tenontosaurs (large, plant-eating dinosaurs) are grazing on ferns or cycads, going about their everyday business," he added.

"Unbeknown to them, you've got a pack of predators stalking them.

"First, [the Dromaeosaurs] try to separate the animal they wish to kill by running into the pack.

"The lead attacker then jumps on to the flanks of the animal, followed by maybe two or three others, hooking the huge claws in their feet into the animal and holding on with the re-curved claws on their > hands.

"And once they're hooked into their prey, the razor sharp teeth of their jaws go to work causing as much blood loss as possible to weaken the animal.

"Eventually, the other animals come over for the kill, probably ripping open the throat and stomach with their teeth - not their claws."

The results of research were first shown on The Truth about Killer Dinosaurs, a BBC television production.
==========================================================



Note that these numbers are for _Velociraptor_, not the larger _Deinonychus_.


Allan Edels