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RE: Lack of Running Giant Theropod Tracks











> Date: Sun, 28 Nov 2010 13:49:01 -0500
> From: d_ohmes@yahoo.com
> To: dinosaur@usc.edu
> Subject: Re: Lack of Running Giant Theropod Tracks

> On 11/28/2010 12:10 PM, Sim Koning wrote:
> > Most if not all ornithopods could probably run and ceratopsids may have 
> > been able to gallop, which means giant theropods would have needed to run 
> > to catch them.
> > I have a hard time believing that giant theropods such as
> tyrannosaurs would have limited their prey to the largest and most
> powerful animals in their ecosystem.


Don Ohmes wrote:


> Which were what? Surely you don't mean sauropods? A Boy Scout with a
> piece of rope and a sharp knife could kill the biggest sauropod that
> ever lived. In relative safety, at that.



Here I was focusing on the high probability that Triceratops was the one of the 
largest, most powerful and dangerous animals in its ecosystem *and* it may have 
been quite fast. I'm guessing that you were intentionally exaggerating with the 
boy scout comment, since some large sauropods would have been able swallow 
animals the size of a human child whole, and may have done so occasionally in 
order to increase the amount of calcium and essential amino acids in their diet.
 
Here is an example of said behavior: http://www.youtube.com/watch?v=saOOn2G16gE


> > So if there was a drop off in speed (loss of the ability to run) when a 
> > carnosaurs/tyrannosaurs reached giant sizes, I'm left > >wondering why 
> > having your prey options limited to the most dangerous herbivores in your 
> > ecosystem would have been an advantage.

> Again, I assume you mean sauropods. I am flabbergasted every time this
> comes up on list, and I mean nothing personal in this. Everybody seems
> to agree w/ you, but can offer nothing to defend this intuition become
> an institution.
 
No, not specifically, since ceratopsids, giant ornithopods and ankylosaurs are 
not sauropods. You are either intentionally or unintentionally forming a straw 
man version of my argument.  


> Try a thought experiment -- drop down on all fours and become a
> sauropod. Your neck is now as long as your torso, and as big around as
> your finger, or maybe something a little more sensitive. How big is your
> head? Really, really, small...

I would rather look at the actual animals and compare them with living analogs. 
To start with, you are greatly exaggerating how small these animals heads were: 
they may seem rather small relative to their body size, but in absolute terms 
they were quite large. As an example, the skull of the Brachiosaur in Chicago 
is large enough for me to fit my head and shoulders into and I'm nearly 6 feet 
tall.  
 
> On ground where it's mobility is not impaired, any small and aggressive
> dog could kill you easily with one bite should it be able to teach your
> neck, even at the base.
 
I do not weigh 35 tons or more, and I do not have neck ribs protecting my 
throat and my carotid arteries. Also does your thought experiment allow me to 
rear up on my knees and smash the small dog with my fists? When you consider 
that giraffes use their head and necks as *weapons* the necks of sauropods may 
have been nearly as dangerous as their tails.
 
  http://www.youtube.com/watch?v=C7HCIGFdBt8


> Predators do not need to eat very often, and extremely large herbivores
> do. How long do you think you can "rear up and thrash your tail"? Who
> gets tired first? Are there trees or rocks? Well, then forget about
> doing any tail-thrashing...

You are begging the question by assuming that sauropods would have been 
extremely slow and almost helpless. You are also assuming that the risk of 
being trampled on by 50 ton animal and being struck by a swinging neck/tail 
would be low enough to make the attack worthwhile for a large theropod. There 
is no reason to presuppose either of these things since giraffes and elephants 
are both more than capable of killing lions and other large predators.   
 
> I do not accept that the general pattern seen in the geo-record is a
> coincidence -- that is, the largest sauropod is matched by a large-jawed
> meateater just about exactly tall enough to reach the base of the throat
> at any given moment. IMO, sauropods got big because once their lifestyle
> was set, they had to be taller than the mega-theropod of the day. They
> had to get those long skinny necks as far off the ground as possible.

That may have been part of it, but I think you are greatly overstating their 
vulnerability. I suspect the giant shark-toothed allosauroids were well adapted 
hunters of juvenile sauropods, and that their extremely high growth rate was 
likely a response to predation. However, since sauropods had a variety of neck 
lengths and shoulder heights, I would guess it had more to do with raw size 
rather than the vulnerability of their necks. 
 

> > Juveniles of prey species are often a primary target for predation and at 
> > least the juvenile ceratopsids were probably capable of rhino like speeds. 
> > I imagine that if Tyrannosaurs were limited to 10 to 15 mph they would have 
> > effectively been prevented from catching the juveniles of their primary 
> > prey. Of course this could be why juvenile tyrannosaurs were more gracile, 
> > but having a lighter build and more blade like teeth wouldn't have helped 
> > much in bringing down the juveniles of animals such as Triceratops.
>
> In my opinion, Trikes were the most dangerous to T. rex, on level ground
> and good footing. A frontal attack was near-suicide. A herd may have
> been extremely aggressive and also faster. An elderly trike w/ resorbed
> horns that was cast-out of the herd would certainly be an exception, though.

I agree, and that was part of my point.
 

> > I'm guessing the more gracile build of juvenile Tyrannosaurs may gave been 
> > an adaptation to allow them to catch species (such as ornithomimids) that 
> > were almost completely out of "range" for the giant adults; a similar 
> > relationsip can be seen between lions and cheetahs.
> > If I'm not mistaken, most if not all predators alive today are capable of 
> > running down and killing most of the smaller animals in their environment. 
> > As an example, lions can be seen killing everything from gazelles to young 
> > elephants and so are not limited to a few dangerous prey species. However, 
> > I am aware that this is one big argument from analogy, and the analogy may 
> > not be a very good one.

> Imagine how easy an elephant would to kill if all you had to do was bite
> the end of it's trunk. Think about it.

 
That's a fallacious argument because it's based on a false analogy: saurpods 
necks and elephant trunks are only similar in that they are elongated...that's 
it; some macronarians had heads large enough for them to actually bite back! 
 
 

> Tactically speaking -- a sauropod in a parking lot would be easy meat to
> a persistent giant theropod.

If sauropods were as helpless as you seem to think they never would have 
evolved in the first place. Predators do not have some sort of "conservation" 
instinct: predators such as wolves will slaughter entire herds of sheep if they 
are helpless and can not get away. I have a feeling the same would have 
happened to sauropods if they were such "easy meat". 
 

> Verso -- a theropod in a swamp or even on muddy ground could not safely
> approach a large sauropod. "You have fallen, and are now flat as a
> fritter." says the big guy w/ the skinny neck.
>
> As to T. rex -- have you thought about this? The scarcity of sauropods
> in the sediments where T. rex is found may be due to T. rex's extreme
> proficiency as a hunter, and a climate that ensured that almost all
> sauropods would periodically have to leave swampy refuges in search of
> muddier pastures? Bones on the hill are rarely preserved.

That or it could simply be because sauropods went extinct for whatever reason 
in North America and a species of titanosaurid migrated from another continent 
via a land bridge or an island chain. The formations that they are found in 
also span nearly 10 million years. Is there any evidence of Alamosaurus 
increasing in size along with the tyrannosaurids?
 
 

> Lastly, but most importantly -- how do you answer the work of JR
> Hutchison and others, which sums to "not possible"?

> Googling "AMNH theropod problem" brings up the "too big to run" case. It
> is convincing...
 
 
I've read two of Hutchinson's papers so far and I found them very interesting, 
but I think the media (and most people in general) seem to think that studies 
or experiments equal "proof". The reality is there is no such thing as "proof" 
in science (outside of mathematics), only evidence. I imagine John Hutchinson 
would be the first to tell you that there are a *lot* of unknowns when forming 
computer models of an animal that has been dead for 65 million years. That 
being said, 25 mph isn't exactly walking, it's actually pretty fast. I would be 
interested to see how models would turn out if they included highly elastic 
tendons somewhat like those seen in macropods (kangaroos), which seem to hold 
up well under increased weight. I'm sure that was factored in to some degree 
since most or all tendons and muscles can work like springs. I'm also stumped 
as to how a 100 ton sauropod could support its weight if a tyrannosaur had just 
enough strength in its legs to walk quickly (10-15mph) and not run. 
 
The "evolution" simulation study done by others is clearly flawed, as it 
suggests that a compsagnathus could run as fast as a race horse. 
 
 
Simeon Koning