[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index][Subject Index][Author Index]

Re: Jobaria and the Elephant Commit Suicide



Richard Travsky writes:
>  Jeff Ogradnik was able to show
>  that the bones of Jobaria were up to the task. It would
>  take a mass almost three times greater to snap Jobaria's femur.
Ah now I remember Alexander McNeill mentioning this in his book.  He said
that estimating the tensile strength of bone in relation to the animal's
pain threshold would depend on the stress involved being one third at
maximum of the critical breaking point.  Is this what we're talking about?
 > Many animals have such displays regardless of the size of the predator.
> You also have to consider the effect of a fully reared sauropod(s) on
> multiple predators. Now *that* would be impressive.
I could swear blind I didn't come up with this myself (I'll be seriously
impressed if it transpires that I did), but a rearing sauropod with it's
tapering neck and small head will give the impression of an increased size
as it will look like it is dissapearing into the vanishing point, much like
that American monument - is it the Gateway Arch in St Louis, Missouri? -
that is actually narrower at the top than the base, but gradually so as to
look like it is scraping the heavens.  Any predator with an eye for
perspective will think a sauropod is drastically larger than it really is
(and it really is large).  Wish I could remember where that came from.

Regarding Matt Bonnan's comments:
>>Okay, but here we must be extremely careful.  Despite all the functional
stuff I could throw in here about elephant skeletons differing from
sauropods (and you would all sigh and kill me), what elephant are talking
about?  African, Indian, what species, what geographic range?  It is very
easy to go from using an elephant as a useful yardstick to jumping to
conclusions about specific behaviors.  Just because Jobaria or other
sauropods "look" like they're designed to rear up doesn't mean they did,
whatever you compare them to.<<
Are there not specific adaptations in the diplodocid form (forgetting
elephants or horses and what they do for a second) that REALLY look like it
should be able to rear?  Saw one of Darren Naish's talks at the Dinosaur
collector's club about new discoveries three years ago where he mentioned
work done on Opisthocoelicaudia or similar having a grasping tail (perhaps
you could confirm or deny this reference for us Darren?) The vertical
processes on the vertebrae in D Carnegii are another for instance:  The
first dorsal vertebrae being only 3/4 of the height of the heavily fused
sacral vertebrae and the first cervical being 1/11th or 1/12th of
afore-mentioned sacral process.  This is directly comparable as D'arcy
Thompson puts it to a single span suspension bridge.  That's what suspension
bridges are designed to do - it's not a case of behavioural comparison, it's
the functional engineering of the skeleton, I would have thought.  okay so
as you say - because they look like they could doesn't mean they did, I take
that as fair, but:
>>remember we are dealing with very huge animals here -- they
are already big and weird.  Why mess with them in the first place -- how
much bigger and scarier do you need to be?<<
It depends on who you are.  Patrick Norton touched upon this in brief, but
here goes anyway:  Noone (to my knowledge anyway) has ever mounted a scaled
down model of a sauropod skeleton to demonstrate how large they would be if
you are looking through the eyes of an allosaur (as opposed to the eyes of a
defenceless titchy primate as let's face it, we all are).  I think we'd be
surprised at the difference it makes.  Also isn't the Barosaurus diorama at
AMNH depicting an allosaur TRYING to pick on a youngster.  it's not messing
with the "Already big and weird" it just ends up having a show-down with it.
>>You can step on or kick a
dinosaur which comes close without the rearing, and some sauropods have what
appear to be tail "weapons": whiplash in diplodocids, clubs in shunosaurs
(unknown/unsure in other Chinese forms).<<
That doesn't seem an awful lot of use if your assaillant is going for your
throat.  I'm DEFINITELY not saying they couldn't reach their throat (D
carnegii and Barosaurus anyway) because provided there was enough side to
side flexibility in the tail the length indicates that they could.  What I
do wonder though is whether they had enough muscle control and sense of aim
to prevent themselves from accidentally whacking themselves in the mouth.
>>Again, the rearing model is interesing, but remains to be tested: there is
a
big tail muscle (caudofemoralis) that runs off the tail and inserts onto the
fourth trochanter of the femur about half way down in sauropods.  No matter
how you choose to have them rear, something has to happen with this
connection -- no good answer so far, from me or anyone else who studies
these beasties, so that is not a criticism, just something to note.<<
I don't follow this - what are the implications of this muscle's presence?
>>While I will be the first to tell you sauropods have strong hands and
limbs,
the thought of all the weight crashing back down gives me the willies!  I
don't care how much cartilage you stuff in there<<
I know I cringed in that episode of WWD when they kept landing like that.
>>Sauropods are weird, huge, and wonderful without having to make them
something bigger, better, and faster.<<
I don't think we are - not wanting to be personal here Matt, but it could
equally be said that sauropods have really big feet, why do they need really
mobile ones too.  The way I see it is if they have it (and that is what we
are trying to ascertain) then there's not much we can do about it.
Yours sincerely,
                         Samuel Barnett