Tyrannosaurs hunting sauropods (was late night thoughts: misunderstand what?)

[Dann Pigdon <dannj@alphalink.com.au>]

I've just thought of several reasons why tyrannosaurs may have been 
ill-designed to hunt sauropods: 

1) 

Tyrannosaurs had blunter, less blade-like teeth than some other 
mega-theropods (carcharodontosaurids, allosaurids, etc) and seemed to have 
relied on a powerful crushing bite rather than a messier blood-letting one. 
This would seem to restrict them to attacking the neck or tail of a 
sauropod, since nothing else would be thin enough to get their jaws around. 
Blade-toothed mega-theropods like Giganotosaurus tended to have larger 
forelimbs (with more digits) that tyrannosaurs, perhaps indicating they 
could have used a 'bite and pull back' strategy to cause huge bleeding 
wounds with the upper jaws alone, while raking with the forelimbs. They 
could have employed a quick attack on just about any body part, followed by 
an even quicker retreat, then waited for bloodloss to do it's job. That's 
the same strategy that Great White sharks use on seals. 

I suspect that the base of really big sauropod necks (or tails) may have 
been too wide for a tyrannosaur to make an effective bite. If the jaws are 
too wide when coming into contact with flesh (and probably thick hide), then 
they have less leverage with which to be closed. I call this the "giant 
peach" hypothesis (after the book "James and the Giant Peach" - when James 
is worried about sharks biting the peach while it floated in the ocean, 
until an intelligent worm explains why there's really nothing to worry 
about). This may have restricted their attacks to either the end of the tail 
(which would have been pointless) or close to the head (which is the bit 
that can see you coming). 

2) 

One really big problem with biting down hard on a neck (or tail for that 
matter) would have been the presence of a dorsal frill of spikes. They've 
only really been identified in one type of diplodocid, but if such 
keratinous (ie. non-bony, hence less likely to be preserved) spikes were 
common amongst sauropods in general, then they would have been a serious 
deterant to biting down hard. 

3) 

If you're going to tackle something with the mass of a sauropod, then a low 
centre of gravity would probably be an advantage. Stumpy-legged 
mega-theropods like allosaurids and carcharodontosaurids may have been 
better able to withstand a massive shove without fatally toppling than the 
top-heavy, long-legged tyrannosaurs. 

4) 

Tyrannosaur bite marks have been confirmed on hadrosaur and ceratopian 
bones, however as far as I'm aware no confirmed bite marks have been found 
on sauropod neck vertebrae. The messy slashing techniques of blade-toothed 
mega-theropods wouldn't have left any neat puncture marks on bone (in fact 
with blade-like teeth you'd go to great lengths *not* to make contact with 
bone). I think it's notable that all of the confirmed tyrannosaur bite marks 
on herivorous dinosaurs have been towards the back end of the prey. In fact, 
as far as I'm aware the only bite marks of any mega-theropods found on the 
heads of animals were on others of the same species (ie. intra-specific 
'face biting'). 

Any comments on the above points are welcome - especially if they complete 
blow them out of the water (I live to learn). 

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