----- 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?
......... I am a functionalist, caring little about who has sex w/ who, so the
working definition is tall enough to reach the base of the largest coeval
sauropods neck. -- DO.
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*.
........... 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. 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, in my view, evidence for an arms race (I term I dislike, but have no
immediate substitute for). Further, vulnerability does not equal extinction.
Consider the amazingly vulnerable and evolutionarily enigmatic 'possum
(American style). Restate your point, and then think about it. If the level of
vulnerability required for an arms race was defined by extinction, there could
no arms races... that said, I am more interested in your evidence _against_
selective symbiosis (arms race). Finally! A potential substitute for 'arms
race'. Maybe. -- DO
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.
...... 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.
> 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.
........... Well, the idea of the pine log was that it is assumed to be
'stronger' than a neck. Obviously multiple opportunities for error here and I
would LOVE to test the concept more realistically. As to neck swing; well, that
sounds a little desperate. }:D -- DO.
> 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? Will it pirouette and smack w/ its tail so fast I can't
back away? The pivot speed for the largest land animal ever was probably the
slowest ever. Can it swat a fly off the side of it's head w/ it's tail? Can it
follow me into the trees? Not likely in any way that will place me in danger.
MAYBE if I trip and fall? -- DO.
> 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?
..... Some. But not much. Heh. "Kick away. I am up here by yer ol' punkin head.
Which you better be movin' while yer kicking, 'cause I ain't gonna miss again." --
DO.
> 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.
Proximity happens, and the rewards were significant. Loose association of
still-hunters, somebody gets lucky, everybody eats for a week... it seems very
do-able to me. -- DO.
> particularly the delicate skulls (likely eaten immediately)
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.