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 6:53 AM

> First, probably a good time to reiterate what my points are as all points 
> tend to wander in these things;
> 1). T rex and equivalents were physically well-suited and environmentally 
> blessed if they 'chose' to use a still-hunting strategy. If this argument 
> can be made convincingly, and I believe it can, it implies that eyesight 
> and foot speed do not define the difference between predator/opportunist 
> and obligate scavenger in T rex or equivalents. Barring very hard times.
> 2). The long-necked dinosaurs had a uniquely vulnerable physique which 
> affected their evolutionary path critically, leading to maximal giantism. 
> That last term is a little redundant, but gee, they were big.
> 3). Therefore, I intend to show, or make the best case possible, that the 
> large bipedal carnivores had the tools and opportunity to prey on even 
> adult sauropods, thereby establishing parameters for the previous two 
> points. Behavioral phenotype and the actual day-to-day activities of T rex 
> equivalents are not provable, in my opinion. At least not by me.

1) Just about nobody thinks *T. rex* was an obligate scavenger. What exactly 
do you mean by equivalents? Other tyrannosaurids of that size range ( = 
*Tarbosaurus*), or all theropods of that size range?
2) They can't have been _that_ vulnerable, or they'd have died out as soon 
as the first seriously big theropod appeared. There is no evidence for an 
arms race, and some against. More importantly, *Opisthocoelicaudia* and the 
nemegtosaurids were fairly small, and yet they, not *Amphicoelias 
fragillimus*, coexisted with *Tarbosaurus*.
3) I agree that the large theropods were able to prey on adult sauropods. It 
can't have been more difficult than elephants killing lions (which happens 
on a regular basis -- see top of 
http://darrennaish.blogspot.com/search?q=elephants+lions), and pity the poor 
lions for their canines that are circular in cross-section! I'm just saying 
it can't have been as extremely easy as you assume.

> But then, I discount 'neck fling'. [My basis for doing that this; I 
> estimate from practical experience that if I were to take a pine log the 
> approximate dimensions of a diplodicus neck, mount it parallel to the 
> ground, and hang 2 Cadillac Escalades on the end of it, it would probably 
> break immediately.]

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.

> I think if the strike missed there was ample time for predator get-away,

...unless the tail or a forelimb hit.

> As to sauropods stomping theropods... well, I just don't think the 
> theropods were THAT slow.

Why shouldn't a sauropod be able to kick much faster than it usually walks?

> E.g., consider the standards you mention for a successful (adult) sauropod 
> kill; close proximity (5-8m) to head, total surprise, and full jaw grip at 
> or very near the head.

Such close proximity to the head can't have been easy to reach in an open 
landscape. Note that "*Alamosaurus*" has not been found in the Hell Creek Fm 
which was a wooded environment; likewise, the Nemegt Fm had gallery forests 
at most, IIRC.

> particularly the delicate skulls (likely eaten immediately)

What for? Nutritional value close to 0.