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RE: Campbell's even crazier than a MANIAC? (archeopteryx




 I think I was half asleep when I wrote most of that last night (I'm an 
insomniac), so I'm not to entirely sure what I was trying to get at LOL. 
Anyway, I think my point was that more derived dromaeosaurids were probably 
descended from arboreal, flying animals, and may have retained their ability to 
climb rather well, albeit not too habitually. For example, lions are not very 
good at climbing trees, but they still retain this ability that was inherited 
from their smaller ancestors. As far as what Archaeopteryx were climbing; the 
fact that they had greatly elongated hooked fingers seem indicative to me that 
they climbed through bushes and trees not unlike a Hoatzin chick.

> Date: Wed, 24 Sep 2008 08:39:26 -0700
> From: erikboehm07@yahoo.com
> Subject: RE: Campbell's even crazier than a MANIAC? (archaeopteryx
> To: dinosaur@usc.edu; simkoning@msn.com
>
>> I also think it's pretty obvious that basal avians such as archaeopterx
>> must have evolved from highly arboreal ancestors, simply because they
>> could fly. The intermediary stage proceeding flight has to be gliding
>> and I don't know of any gliding animals (except flying fish) that are
>> not highly arboreal.
>
> Are there any gliding animals that make use of a cliff face? I would suspect 
> there are, despite not being able to think of any off hand.
>
> They could have come from an ancestor that lived in terrain like that a 
> mountain goat is suited to. I've seen videos of eagles knocking/dragging 
> mountain goats off a ledge to their death (the eagle would have a much harder 
> task killing it outright) gliding in this case would be very useful, despite 
> no trees.
>
> Why bother discussing the larger dromeosaurs from the cretaceous? Archie and 
> Micro predate them, and don't have such distinct claws.
> So if the even if the common ancestor was arboreal, those huge curved claws 
> were not an ancestral arboreal adaptation.
>
> For that matter if Archie was Mid Jurassic, and Micro is Early Cretaceous, 
> should much emphasis be placed on Micro at all (other than evidence that 
> dromeosaurs may have been mainly just early 2ndarily flightless birds)
>
>
> --- On Tue, 9/23/08, Sim Koning  wrote:
>
>> From: Sim Koning 
>> Subject: RE: Campbell's even crazier than a MANIAC? (archeopteryx
>> To: dinosaur@usc.edu
>> Date: Tuesday, September 23, 2008, 9:01 PM
>>> Date: Wed, 24 Sep 2008 09:39:10 +1000
>>> From: dannj@alphalink.com.au
>>> Subject: Re: woops! Sorry everybody (: Aaah! The EYE
>> is back!þ C
>>> To: dinosaur@usc.edu
>>>
>>> Quoting Sim Koning :
>>>
>>>>> Date: Mon, 22 Sep 2008 13:01:30 +1000
>>>>> From: dannj@alphalink.com.au
>>>>> Subject:>>> To: dinosaur@usc.edu
>>>>>
>>>>> Quoting Tim Williams :
>>>>>
>>>>>>> Sim Koning wrote:
>>>>>
>>>>>>> An eagle's talons are highly
>> specialized for predation, so are the claws
>>>> of large cats,
>>>>>>> neither seem to have a problem
>> climbing around or perching in trees.
>>>>>
>>>>>> Neither of these has claws *as*
>> specialized as the sickle claw (and its
>>>>>> supporting digit) of dromaeosaurids. Not
>> even seriemas (cariamas).
>>>>>
>>>>> Indeed. Eagle and cat claws tend to have
>> circular or ovoid cross sections
>>>> (as do the claws of just
>>>>> about any climbing, perching or grasping
>> creatures). The narrow blade-like
>>>> sickle claws of the
>>>>> larger dromaeosaurs would seem to be
>> ill-suited to standing up to twisting
>>>> or sideways forces.
>>>>
>>>>
>> http://www.evolutionnyc.com/ImgUpload/P_886549_950527.jpg
>>>>
>>>> Cat claws are just as blade like, if not more so,
>> than dromaeosaur claws.
>>>
>>> The swivel-claw of Velociraptor is longer, narrower,
>> and much less curved than that of a cat. Its
>>> shape matches that of a piercing weapon, more than a
>> grasping hook.
>> -------------------------------------
>>
>> True, but many specially adapted climbing animals do not
>> have sharply curved grasping hooks for claws. Iguanas are a
>> great example of this
>>
>> http://alumnus.caltech.edu/~keith/photos/claws.jpg
>>
>> and bears
>>
>> http://www.evolutionnyc.com/ImgUpload/P_886505_950485.jpg.
>>
>> Notice that in both cases the claw is very long and less
>> curved than a cats.
>>
>> Just to be clear, I'm not trying to say dromaeosaurid
>> claws were adapted primarily for climbing. I'm simply
>> trying to say that it is a little unrealistic to say these
>> creatures weren't fully capable of climbing up trees. We
>> humans don't even have claws on our feet, yet we have no
>> problem using them to climb trees. I also think it's
>> pretty obvious that basal avians such as archaeopterx must
>> have evolved from highly arboreal acestors, simply becasue
>> they could fly. The intermediary stage proceeding flight has
>> to be gliding and I don't know of any gliding animals
>> (execpt flying fish) that are not highly arboreal.
>>
>>
>>> Also, cats have a total of 18 claws to support their
>> weight, spread over four limbs that are roughly
>>> of equal strength (in climbing species like leopards
>> the forelimbs can be even stronger than the
>>> hindlimbs). Dromaeosaurs were primarily bipeds, so
>> their hind limbs would have been better
>>> adapted to supporting their weight than their
>> forelimbs (at least in larger species).
>>
>> This doesn't mean much, my legs are much stronger than
>> my arms and I have no problem climbing up a tree.
>>
>>> If the swivel-claws were specifically climbing
>> adaptations then that would mean that a Velociraptor would
>> be
>>> bearing most of it's weight on just two long,
>> narrow, slightly recurved claws while climbing.
>>
>> Not really, it could have had just as much weight, if not
>> more, on its other toes.
>>
>>> Their length and narrowness would have made them
>> vulnerable to twisting forces, which the shorter,
>>> thicker, more recurved and more numerous claws of a
>> cat are better at resisting.
>>
>> I think the killing claws of a dromaeosaur would have been
>> subjected to far more twisting force while being plunged
>> into a strugling, thick skinned and scaly dinosaur than they
>> would be while simply hanging on to the rough surface of
>> tree bark. If their claws couldn't simply support their
>> weight while climbing a tree, I seriously doubt they could
>> use them to kill a dinosaur.
>>
>>> I think it's more likely that when larger
>> dromaeosaur species climbed (and most animals can climb
>>> if pressed hard enough), that they did so more like a
>> bear - digging in with the forelimbs but using
>>> the smaller toe claws on the hind feet for traction
>> (since we know these can easily support the
>>> animal's weight). I would think that a climbing
>> Velociraptor would try to avoid bringing the swivel-
>>> claws into play against a tree trunk.
>>>
>>> This of course doesn't necessarily apply to the
>> smaller bodied dromaeosaurs with their shorter and
>>> thicker swivel-claws. Here's a picture of the
>> swivel-claw of Dromaeosaurus:
>>>
>> http://www.schoolersinc.com/images/Dromaeosaurus_claw_1000.jpg
>>>
>>> Compare it with the swivel-claw of Velociraptor:
>>> http://www.geocities.com/dannsdinosaurs/vmongclw.gif
>>>
>>>
>>>> Cats sharpen their claws by digging them into
>> trees. Dromaeosaurs (and other
>>>> theropods) may have done the same.
>>>
>>> I don't know of any other animals that sharped
>> their claws in this manner. If there are non-cat
>>> species that do this, then it may be behaviour only
>> seen in mammals.
>>
>> Bears do it. My parents have a tree with huge claw marks
>> that were created when a black bear shapened its claws, just
>> like a big cat.
>>
>>
>>> Cat claws grow from the
>>> inside out, with new layers of keratin layed down on
>> the inside of the claw sheath. As cats dig their
>>> claws into a substrate like wood and deliberately pull
>> then straight out again, the older outer layer
>>> of keratin is stripped off to leave younger, sharper
>> layers behind. I have quite a collection of outer
>>> claw sheaths from my own cat - they're a bit like
>> discarded spider skins in that they retain the
>>> original shape, but are essentially fragile husks.
>>>
>>> I don't recall ever seeing birds or reptiles
>> sharpening claws in this manner. That's not to say it
>>> doesn't happen of course, although a quick Google
>> search of "claw sharpening behaviour" mostly
>>> seems to return cat-related pages. The search
>> "claw sharpening behaviour -cat" doesn't seem
>> to
>>> return anything useful, except for references to
>> civets (which seem to be kissing-cousins to cats).
>>
>> The point is I doubt tree climbing would have had much of a
>> dulling effect on their claws. If it did, they could simply
>> keep their use for this purpose to minimum by using their
>> other toes just as you said.
>>
>> Once again I am not trying to say that the killing claw of
>> a dromaeosaur was designed primarly for climbing, just that
>> it could have use it to climb if the situation called for
>> it.
>>
>>>
>> ___________________________________________________________________
>>>
>>> Dann Pigdon
>>> GIS / Archaeologist
>> http://geo_cities.com/dannsdinosaurs
>>> Melbourne, Australia http://heretichides.soffiles.com
>>>
>> ___________________________________________________________________
>>>
>>>
>>>
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