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Re: Lack of Running Giant Theropod Track
Richard W. Travsky wrote
>So, one print by itself would be evidence of running? ;)
If that single footprint is evidence that a 4-5 ton animal hopped 4 feet
through the air off of one leg...yes! However, if it is just as probable, or
more probable that it was the result of a geological anomaly, then no, because
then I wouldn't say it's very good evidence for anything beyond the fact that
tracks come up missing.
I think it should be pointed out that one piece of evidence is still
evidence. Example: So, one bullet wound by itself would be evidence of a
projectile weapon? I would answer that question with a yes.
But seriously, if someone has any bird eye views of that trackway I would
*love* to see them... please don't make me beg =(...
Don Ohmes wrote
> Tactical implications -- 1) a sauropod faced w/ a large-jawed tall biped
> directly in it's path could not likely just ignore it and keep on
> truckin'... the long skinny neck would require some sort of
> rearing/turning behavior to defend.
I think what Michael Habib has been trying to get across (in a very intelligent
and professional way) is that you are basically making a "Godzilla-vs-Cthulhu"
or "ninjas vs. pirates" argument; that's not how science works. He has been
supporting his argument with statistical data from a very broad range of
predator and prey relationships. I can also back him up with my own experience
as martial artist: I'm lighter and faster than a 300lb bodybuilder, and the
human body has all sorts of "weak points" that I could attack, but the reality
is one blow from his fist could put me in the hospital or kill me, so I would
rather not pick a fight with someone like that; I'm pretty sure the same basic
principle is the reason why most solitary predators do not attack animals much
larger than themselves. Now, is this proof of anything? No, but it IS evidence.
Again, proof isn't a realistic goal to begin with outside of math, so we are
left with scaling the probability of things based on e!
vidence. Given the available evidence I would say that it is highly
*improbable* that something like a lone Allosaurus fragilis would attack a 50
ton animal...by itself.
Martin Baeker wrote
>As co-author of one of the papers I'd like to remark on the tendon
>thing because it seems to come up quite often: The clever thing John
>did was to focus on the force at the mid-stance moment. The energy
>storage due to elastic tendons will not help you there, because the
>tendons are still attached to muscle which must still exert the
>necessary force. What tendons *could* to is to change the typical
>sinusoidal shape of the ground reaction force curve to something
>different that rises more steeply and so covers more area (giving a
>larger mean force) without increasing the maximum. We did some
>back-of-the-envelope calculations on this - the maximum GRF will not
>increase by more than roughly 20% IIRC.
Thank you very much for the response. 20% isn't bad, so would I be correct in
thinking that might help offset the (for its size) inefficient limb design of
giant theropods? The reason I've been wondering about this is primarily because
I'm having a hard time accepting (for several reasons) the idea that T. rex
walked around on very straight legs. However, as the research shows, if the
legs were more or less flexed even when standing around, they would be eating
up quite a few calories just by resisting gravity. Perching birds have tendons
in their feet that pull tight when they land, macropods have ways of saving
energy while hopping etc.. so I've been wondering if giant theropods may have
had something roughly analogous for conserving energy despite the cursorial
limb design they may have been stuck with from the juvenile "running phase" of
their life cycle. After all, these animals must have spent the majority of
their youth (most of a Tyrannosaur's life) running around !
like ratites, so it seems strange to me that an animal that is well adapted for
running would have grown to a size that would render its limbs inefficient and
its running adaptations mostly useless. To put this another way, why don't
sauropods and stegosaurs start out with bird like, gracile legs before growing
into their more "elphantine" adult forms? I think it's more likely that giant
theropods retained the ability to run (however limited) into adulthood.
>(But having a 6-ton theropod run at you at 25mph would probably
>convince you that this is not really slow...)
No it's not! That's a heck of a lot faster than I can run, and if I'm not
mistaken it's about as fast as the world's largest rhinos. I would say the same
thing goes for turning speed: a 1000lb head taking 4 seconds to swing 360
degrees in a 20 foot radius is not what I would call "slow".
I think here is where I should clear things up with the other people on this
list. I'm not making an argument for a gazelle speed T. rex here, just the
ability to *run*. 20-25 mph would not be a casual walk! I think the 20-30 mph
range is the most likely for reasons I have already stated. I do not think that
a 10-15 mph speed range is realistic for large tyrannosaurs as it would cut off
most the animals in their ecosystem smaller than themselves and it would mean
that they could not run at all, despite being essentially scaled up versions of
a running animals.
>BTW, the leg proportions of ornithopods seem to be less well-adapted
>to fast running than those of T rex, so even if T rex was not a
>super-sprinter, it may still have been fast enough. (And of course
>there are scenarios where the juveniles do the running, and at 2 tons
>of mass the pciture changes quite a bit.) If anybody has reasonable
>measurements and estimates for muscles in ornithopod legs, we could
>easily run them through our software...
Yes, but the majority of the herbivores in a Tyrannosaurus' ecosystem were
Triceratops, and it seems that a young a Triceratops with a body mass similar
to that of a rhino may have been nearly as fast. Also unless Tyrannosaurs were
set up like eusocial insects, I have a hard time believing that the juveniles
did the hunting for the adults; it seems like they would be better off hunting
for themselves like young crocodiles. The juveniles also seem as if they are
adapted for hunting different prey in a similar fashion to what we may be
seeing in Albertosaurus and Daspletosaurus. Now for me, if Tyrannosaurs were
capable of at least 20-25 mph, the problem largely goes away. I just don't see
how an elephant slow T. rex would have been able to catch the young of the most
abundant herbivores in its ecosystem if they could only walk, albeit at a brisk
pace. I also don't see the young of too many predators bringing food to their
parents rather than the other way around.