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

Re: late night thoughts: misunderstand what?



Thanks, Dann, and thanks for the forward.

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.

For sure they ate hadros, and anything else they could grab. We just have 
different ideas about the toughness of sauropods, in certain tactical 
situations. 

Years ago, I cooked up what I considered at the time a detailed analysis (how 
wrong I was) of various scenarios for sauropod/T rex equivalent interactions. I 
will dust it off and post it. I will be grateful if you will pick at it... 
given a solo confrontation, still-hunting strategy, my conclusion was _very_ 
low risk to T rex equivalents and a moderate to fair chance of success (taken 
from before attainment of lethal proximity, post-prey detection). 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.] 

I think if the strike missed there was ample time for predator get-away, and if 
it didn't miss, dead sauropod. If I am wrong about neck strength, and the neck 
became a problem, just let go! As to sauropods stomping theropods... well, I 
just don't think the theropods were THAT slow. 

As to your last question: "How many pre-mortem bite marks have even been found 
on a large adult sauropod fossil?"

This brings up an important point that bears on the fossil record generally, 
and that I have never found in lit. (although it could well be there). I 
believe it could be investigated on a experimental basis, but the following is 
based on personal observation and logic. It applies to terrestrial prey and 
predators (including humans). 

Competent predation is rarely preserved. Further, the more stringent the 
'standards' are for a successful exploit, the less the likelihood that the 
exploit is to be preserved. 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. These create the 
conditions for a nearly binary event. In other words, either complete and 
immediate success, or total and immediate failure. Not many crippled sauropods 
(with toothmarks on their skulls) running into areas w/ a "high" likelihood of 
preservation and then dying. In the event of a successful predation exploit, 
which is unlikely to take place on anything less than firm, level' ground 
(still-hunters get to pick their arenas!), there is again a low likelihood of 
preservation, particularly the delicate skulls (likely eaten immediately) and 
vertebrae, the only sections with pre-mortem marks. Not that anyone could tell
 unless the fossil-donating animal survived the attack.

My opinion: you want an idea of what the rex equivalents really ate on a daily 
basis, look for what is missing... what you think you should find more of, but 
you don't. Unless Alley-Oop starts taking my calls again, nobody will ever know 
for sure, though.

It's late. I would like to talk about trees and foraging habits later.

Don

----- Original Message ----
From: Dann Pigdon <dannj@alphalink.com.au>
To: dinosaur@usc.edu
Sent: Saturday, June 16, 2007 6:08:24 PM
Subject: Re: late night thoughts: misunderstand what?



don ohmes wrote:

> "HOWEVER - sauropods are unlikely to have
> coorperated by standing nice and still to allow for such a well-aimed bite.
> I'm not sure how stealthy a multi-tonne tyrannosaur could have been, but I'm
> guessing most saurpods would have known about them long before the predator
> was within striking range..." -- D Pigdon
>
> Aha! So you think *T. rex* (damn, I'm getting to like those little stars; 
> wonder what they are for) capacity for stealth was an issue in relation to 
> sauropods, but not w/ hadrosaurs? What, Are Hadrosaurs stupid, or blind, or 
> something? You dissing hadros?

An adult hadrosaur and an adult sauropod are two very different kettles of 
fish. I'm guessing *most* hadro's were roughly of similar mass (or at least 
less than twice the mass) of a really big tyrannosaur. Whereas a really big 
sauropod (assuming rexes went
for adults) would have been a much heftier target. As a general rule; the more 
mass, the bigger the whallop.

We *know* that tyrannosaurs target hadro's (healed bite marks on the tail). We 
also know that hadro's lacked anything that looks obviously like a means of 
aggressive defense (not even a thumb spike to speak of). Those forelimbs were 
puny, the hindlimbs were
probably too busy trying to skedaddle, the tail was far less mobile than that 
of a sauropod (all those stiffened tendons) and using their (relatively blunt) 
beaks would have meant putting their heads within chomping distance a rex's 
business end.

Also - hadro's could run. That means that a startled hadro could eventually run 
out of puff, or trip and fall in a panic. Either way they'd have presented a 
relatively easy meal. Sauropods couldn't run to save themselves (literally), so 
I'm guessing they used
more of a 'stand and fight' tactic. Did rexes give chase to hadro's? Maybe. 
What sort of evidence might back up such a claim? Something like healed bite 
marks around the tail region perhaps... :)

How many  pre-mortem bite marks have even been found on a large adult sauropod 
fossil?

--
___________________________________________________________________

Dann Pigdon
GIS / Archaeologist         http://www.geocities.com/dannsdinosaurs
Melbourne, Australia        http://heretichides.soffiles.com
___________________________________________________________________