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Re: cause of Gigantism in sauropods



Good points. I wasn't suggesting that bone crushing was the only means of dispatching a meal. I would guess that that T. rex probably killed in more than one way, depending on the nature and size of the prey. I think that at some point in this thread the discussion was about sauropod neck and heads and I made to comment relative to that ---- one might get a killing bite to a sauropod neck without leaving many or any tooth marks. However, as I recall, sauropods are rare elements in faunas with T. rex.

In terms of durophagy in A. mississippiensis vs. C. niloticus, does this reflect more frequent consumption of relatively smaller prey in the former, which might include turtles, vs the latter, where larger prey is more available, at least for some time of the year?

Dan


On 2/11/2011 11:22 PM, Jaime Headden wrote:
   *Tyrannosaurus rex* has been called "heterodont by some authors, an allusion not only to the 
ziphodont crowns of the typical jaw margins and the D-shaped premax teeth, but also to the 
lower-crowned, broad teeth in the rear of the jaws. These latter teeth show less recurvature and blunter 
apices than other teeth in the jaws excepting the "incisiforms" of the premaxillae, and were 
suggested by some authors of relating to bone-crushing. Similar teeth, although much more incrassate, 
are found in living crocodilians, some of which lack the morphology but others (such as *Alligator 
mississippiensis*) showing an extreme form of it. This has been linked to their increased durophagous 
behavior over, say, more "flesh-eating" *Crocodilus niloticus*.

   But I have never heard of a primary bone-crushing manner of dispatching prey, nor with 
the brevity of such exapted teeth in the rear only portions of the jaw do I think that 
*Tyrannosaurus rex* could have employed a crushing-bite method so easily. Because of 
their position in crocodilians and blunt-toothed lizards (*Varanus exanthematicus* as 
well, also durophagous), specialized care in processing is usually done to select foods 
(turtles in the crocs, gastropods and even eggs in the lizards) and in a precise manner 
(they are "handled" into position). I can see this behavior as an extension of 
carcass-stripping and marrow-scavenging, but not as a primary dispatching method.

   Despite this, tyrannosaurids all still seem pretty head-dominated as adults, so much 
so that their jaws WERE the primary tool of killing, as they pretty much lacked any 
other. My off the cuff impression is that of jaw-based grappling and then disabling 
through progressively more grievous wounds. Horner can even have his say here as a 
tyrannosaur can spend a day or two (as wolves can do) following previously injured prey 
in order to ensure it keeps the eventual kill. None of this requires 
"slash-and-burn" as inferred for *Allosaurus*/*Carnotaurus*. However, I am glad 
to be wrong on this, as I also suspect *Tyrannosaurus rex* may have occasionally used the 
leopard strategy: A precise crushing bite to the skull -- this way, Dan's suggesting can 
be true as well.

Cheers,

Jaime A. Headden
The Bite Stuff (site v2)
http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)





----------------------------------------
Date: Fri, 11 Feb 2011 11:17:40 -0700
From: danchure@easilink.com
To: rtravsky@uwyo.edu
CC: dinosaur@usc.edu
Subject: Re: cause of Gigantism in sauropods

Or just crushing of bone?

Dan


On 2/11/2011 10:26 AM, Richard W. Travsky wrote:
On Thu, 10 Feb 2011, Habib, Michael wrote:
On Feb 10, 2011, at 2:16 PM, Don Ohmes wrote:

On 2/10/2011 12:34 PM, Raptorial Talon wrote:
[...]
There's the rub, though - I was just looking at some large theropod
specimens today, along with an adult Apatosaurus louisae (the
holotype, actually). Even if the teeth are imbedded all the way to
their base, it's not altogether clear if they'd get deep enough to
hit the primary vessels. The vertebral aa. are encased in bone, and
the carotids were probably located in a ventral location and encased
in a carotid groove (as in birds) surrounded by muscle. Veins might
be in the line of fire, but the pressure in the veins would not be
that excessive; the blood is basically just dripping back via
gravitational acceleration at that point, minus the resistance of the
vessel walls. The idea of a bite to the neck may seem intuitively
catastrophic, but a number of thick-necked vertebrates use them as
weapons (giraffes and pinnipeds for example). That's anecdotal, but I
think we need to be careful not to assume that a
What about the windpipe and suffocation?

[...]