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Re: Brachiosaur flexibility and face-shape (Was: Terra Nova: thoughts)



If the question is about sprawling ability, that's one thing, but if it's about 
reaching ground level with forelimb assistance, sprawling has never seemed to 
me to be the most obvious, efficient, or comfortable position for a 
columnar-limbed animal.

I have seen images of giraffes adopting bent leg postures to drink, and I'm 
curious if there's any reason a giraffe would sprawl versus flex their 
forelimbs. Does stable flexion not add enough distance for most giraffes?

Could sauropods not flex their forelimbs primarily at the shoulder and elbow, 
effectively leaning forward to lower their shoulder girdle?

I wonder if sprawling would be presumed for a giraffe if we had only giraffe 
fossils. Is there any way to answer that question?

Thanks for all the insights,

Demetrios


-----Original Message-----
From: Heinrich Mallison <heinrich.mallison@googlemail.com>
Sender: owner-DINOSAUR@usc.edu
Date: Wed, 28 Sep 2011 14:43:47 
To: DML<dinosaur@usc.edu>
Reply-To: heinrich.mallison@googlemail.com
Subject: Re: Brachiosaur flexibility and face-shape (Was: Terra Nova: thoughts)

I don't like this "if I have no ossified proof, I assume that X
couldn't do Y" method. Could sauropods sprawl their forelimbs? Very
likely, yes - but we don't know! Do they should special adaptations
for sustaining huge forces while doing so? No, not at all. Do they
show indications that they could NOT do it? Again, none at all.

And if one compares humeral head size and glenoid size it becomes
immediately obvious that there must have been a LOT of cartilage in
the shoulder. Therefore, it is all speculation. So why speculate with
a "can't do attitude"? The "can do" one is equally valid!

Heinrich

On Wed, Sep 28, 2011 at 2:37 PM, Mike Taylor <mike@indexdata.com> wrote:
> On 28 September 2011 13:21, David Marjanovic <david.marjanovic@gmx.at> wrote:
>> Am 28.09.2011 10:37, schrieb Mike Taylor:
>>
>>>  On 27 September 2011 22:27, David Marjanovic
>>>  <david.marjanovic@gmx.at> wrote:
>>>
>>> >> That would be one of the few things that Kent and we WOULD agree
>>> >> on. Assuming that brachiosaurs drank, they would have needed the
>>> >> ventral flexibility to get their heads down to ground level.
>>> >
>>> > I assume their shoulder mobility didn't allow the giraffe
>>> > workaround to this problem?
>>>
>>>  [...]
>>>
>>>  ... and now I realise you were talking about flexibility of the
>>>  forelimb, right?
>>
>> Yes. Giraffes are _not_ able to reach the ground with the head while
>> standing normally; they have to sprawl their forelimbs. Thus, all else being
>> equal, we can't simply assume that sauropods _must_ have been able to reach
>> the ground.
>
> Well, I think we can.  Remember that sauropods had twice as many
> cervicals as giraffes, and they were proportionally longer to boot.
> The giraffe in fact has a pitifully short neck compared with the rest
> of its body, unlike most, maybe all, sauropods.
>
>> My question was how much else _was_ equal: were sauropods able
>> to sprawl their forelimbs? Apparently, *Brachiosaurus* was the only one.
>
> Well, maybe.  I wouldn't want to put TOO much weight on a single
> deflected glenoid.  It could be pathology of the individual, or it
> could be that Brachiosaurus just ossified more of what would be
> cartilaginous in other sauropods.
>
>> Of course, the sheer number of neck vertebrae makes me confident that
>> sauropods were easily able to reach the ground, and if not, there's the
>> remote possibility that they didn't even need to drink -- various desert
>> mammals manage this today, and that without the ability to pee uric acid
>> crystals.
>
> Ah, yes.  Forgot to mention that.  There is at least one published
> sauropod worker who believes this was the case for Giraffatitan at
> least, but since he or she has yet to publish that idea I won't
> divulge the identity of the person in question.
>
>> My point is just that it shouldn't be an unquestioned assumption
>> that sauropods were able to lower their heads the ground while standing.
>
> Not quite, no.  But pretty darned close.
>