Re: late night thoughts: misunderstand what?

[David Marjanovic <david.marjanovic@gmx.at>]

----- Original Message -----
From: "don ohmes" <d_ohmes@yahoo.com>
Sent: Sunday, June 17, 2007 10:13 PM

> ........... I think it unlikely that the first seriously big theropod 
> appeared before or after the first seriously big sauropod (within the 
> margin of error). They probably moved pretty much in lock-step.

There are tracks of very large sauropods in Middle Jurassic strata. IIRC 
there are no hints at seriously big theropods from that time; those start 
with *Saurophaganax* in the Late Jurassic.

> From the functional perspective, top herbivore/top predator form a 
> predation pair. The fact that the most extreme cases of giantism in both 
> occurred simultaneously in geological time

Is that a fact?

*Giganotosaurus* and *Argentinosaurus* do occur together. But neither 
*Tyrannosaurus* nor *Tarbosaurus* have huge sauropods at their disposal; 
*Puertasaurus* lived across the sea. Are there even enough giant theropods 
to qualify for a statistically meaningful sample?

> is, in my view, evidence for an arms race (I term I dislike, but have no 
> immediate substitute for).

Why should only the upper end of the size spectrum participate? If the 
biggest sauropods are just a bit too big for the biggest theropod, and 
somewhat smaller prey is available, shouldn't we expect the predator to 
shift to that smaller prey? If said prey has no other defense than to grow 
larger, soon _all_ sauropods will be at the upper end of the sauropod size 
range. I can't see how you can avoid this -- falsified -- prediction.

> Further, vulnerability does not equal extinction. Consider the amazingly 
> vulnerable and evolutionarily enigmatic 'possum (American style). Restate 
> your point, and then think about it.

How is the opossum "amazingly vulnerable"? It can play dead very 
convincingly, it can climb, it has canines a bit longer than mine, and it 
breeds faster than predators can keep up. I also can't see anything 
"evolutionarily enigmatic" about this.

> If the level of vulnerability required for an arms race was defined by 
> extinction, there could no arms races...

I don't see where you get that from. Arms races never have winners -- those 
that have winners end too soon to be noticeable.

> that said, I am more interested in your evidence _against_ selective 
> symbiosis (arms race).

You predict (see above) a trend of consistent increase in sauropod size. 
There is no such trend. Quantum electrodynamics, I mean, QED.

> ...... I think that when it was practical (prey density= proximity 
> probability, mostly), it was very easy. The ability of prey animals in 
> general to detect immobile objects is over-rated by many in my opinion. I 
> base this on personal experience w/ white-tail deer and wild turkeys, 
> which if you are patient you can get VERY close to, in zero cover. 
> Understandably this is not convincing to a scientist, or even some 
> inveterate hunters. Can't move your eyes at all w/ the turkeys. They get 
> the picture then. -- DO.

Try to overlook a full-grown *Tyrannosaurus* in a landscape a sauropod can 
walk through. That can't be easy.

> That pine log has no muscles in it... but that probably doesn't matter. 
> What
> matters is that you assume that sauropods held their necks very close to 
> the
> ground most of the time -- which was clearly the case for some, but not
> necessarily for all --, and that you overlook the possibility that a
> sauropod might swing the neck around as a weapon, the same way as the 
> tail.
> Sure, sauropods would have avoided using the head as a tail club for 
> obvious
> reasons, but being struck by the middle of a sauropod neck can't have been 
> a
> very pleasant experience either.
>
> ........... Well, the idea of the pine log was that it is assumed to be 
> 'stronger' than a neck.

My point is that it isn't necessarily; muscle work can keep joints from 
ripping apart.

> > I think if the strike missed there was ample time for predator get-away,
>
> ...unless the tail or a forelimb hit.
>
> How? The head is 10 m from the feet in standing position. Now we are 
> delving into an area of sauropod mysticism I have just never gotten, even 
> when I was 8. If I am lurking under a tree like a rattlesnake (for 
> example), and a foraging sauropod wanders close enough for me to try to 
> grab it's head, and I miss, how am I in any danger?

How probable is it that a sauropod would get its head that close to a 
predator? Much, much less probable than getting its head that close to a 
rattlesnake-sized object. I'd attack a sauropod by running at it from a 
side, with wide-open jaws. That's what *Allosaurus* seems to have done, 
judging from its very strong skull that is way overdesigned for the puny 
bite forces *A.* could generate.

> Will it pirouette and smack w/ its tail so fast I can't back away?

Surely a flagellicaudatan can bend its tail by more than 180°? Not that it 
matters much, though -- see above.

> Can it follow me into the trees?

Why should it? As long as you stay there, the sauropod is fine.

> Why shouldn't a sauropod be able to kick much faster than it usually 
> walks?
>
> ..... Some. But not much.  Heh. "Kick away. I am up here by yer ol' punkin 
> head.

You're probably not. Because if you were, all sauropods would have died out 
in the Late Jurassic at the very latest.

> What for? Nutritional value close to 0.
>
> ........ Already mashed up and in my mouth? From me drinking the arterial 
> blood gushing like a high pressure hose out of your body? Apologies to the 
> kids, but this sauropod invulnerability thing is proving hard to crack 
> from the cultural perspective. Vivid images may be required. -- DO.

"Drinking"? What about "being washed away by it"? Or at least blinded, as 
mentioned.