Re: Lack of Running Giant Theropod Tracks

[vultur-10@neo.tamu.edu]

Is Bakker's figure of 5/6 of the large-dinosaur-herbivore population being 
Triceratops in that time and place still supported? If so, it might have been a 
common prey of T. rex simply by necessity. 

Banks Miller

----- Original Message -----
From: "Sim Koning" <simkoning@msn.com>
To: dannj@alphalink.com.au, dinosaur@usc.edu
Sent: Thursday, December 2, 2010 11:47:43 PM GMT -06:00 US/Canada Central
Subject: RE: Lack of Running Giant Theropod Tracks


>>many carnivores regularly take on potentially dangerous prey
 
  I'm not really suggesting that if a T. rex made a habit of killing 
Triceratops it would equate pure suicide, just that it was probably very 
dangerous for a solitary T. rex; as you point out, an experienced adult may 
have been quite good at it. Solitary adults may have made "hit-and-run" attacks 
to avoid being impaled by the horns since their jaws probably possessed more 
than enough firepower to cripple and maim with a single bite. But I think this 
scenario has its problems, such as the potential difficulty for a 6 ton animal 
to slow down if the Triceratops suddenly decides to do an about face rather 
than run.
 
> Indeed; many carnivores regularly take on potentially dangerous prey. Lions 
> will target Cape
> buffalo, even though they could look for easier prey if safety was their 
> primary concern.
 
 http://www.youtube.com/watch?v=4LwAJWSF8QU
 
   As I said in my last post, the best analog for a Triceratops would be a wild 
boar. I think there would have been rather strong selective pressure for adult 
Tyrannosaurs to (at least) work in pairs, for the same reason lions usually 
work together to bring down dangerous game. A Triceratops's greater ability to 
rapidly pivot and turn would have created a huge problem for a T. rex.
 
   There is another reason to suspect that Tyrannosaurus rex was social: 
Tyrannosaurids were descended from smaller feathered theropods that may have 
incubated their eggs, so they may have inherited a similar degree of parenting 
behavior, minus the ability to actually sit on or around the eggs. One of the 
sexes may have guarded the nest while the other hunted. When I was in Chicago, 
I noticed that Sue's left fibula had been broken and healed. I doubt that a T. 
rex with a broken leg would have lasted very long unless it was being fed or 
cared for by another T. rex. Such an injury may not have been a problem if 
"she" was largely immobile for the most part due to parenting responsibilities. 
Considering their close relationship to birds, I find such a scenario to hardly 
be a stretch.
 
 
> Also keep in mind that people tend to think of the huge 12m tyrannosaurs as 
> 'adults', and anything
> smaller as 'sub-adults'. If tyrannosaurs continued to grow throughout their 
> lifetime, as modern
> crocs do, then they may well have reached sexual maturity (ie. 'adulthood') 
> at much smaller sizes.
> The 12m long behemoths may have just been unusually long-lived individuals, 
> rather than
> representative of the normal adult state.
 
 
I was under the impression that this was not the case. I thought Tyrannosaurs 
remained under 2 tons until about age 14, whereupon they hit adolescence and 
underwent an enormous growth phase, reaching sexual maturity (based on 
medullary bone) at age 18. After sexual maturity was reached, there seems to 
have been a plateau in growth. All the evidence supports a much more avian than 
crocodilian life cycle. At least that's what I thought...
 
 
Simeon Koning  
   
 
   
 
  
 
 
 



----------------------------------------
> Date: Fri, 3 Dec 2010 13:56:00 +1100
> From: dannj@alphalink.com.au
> To: dinosaur@usc.edu
> Subject: Re: Lack of Running Giant Theropod Tracks
>
> On Fri, Dec 3rd, 2010 at 1:06 PM, Augusto Haro wrote:
>
> > 2010/12/2 Sim Koning :
> > >
> > > Adult tyrannosaurs, although slower, would have been able to kill 
> > > ceratopsids and
> ankylosaurs,
> > animals that the juveniles may have been too weak and blade-toothed to 
> > exploit. However,
> making a
> > living by attacking something that is not only your own size, but also able 
> > to kill you as easily
> > as you could kill it, may not have made for a very survivable lifestyle.
> >
> > This does not seem easy to infer. For example, the weaponry of a rat
> > or squirrel (their incisors) make them probably very dangerous for a
> > similarly sized predator, yet many weasels make a living mostly of
> > eating these similarly sized rodents...
>
> Indeed; many carnivores regularly take on potentially dangerous prey. Lions 
> will target Cape
> buffalo, even though they could look for easier prey if safety was their 
> primary concern. Yet
> experienced lions still target such dangerous prey, because the potential 
> gain from killing such a
> large creature often outweighs the increased risk. I think the key word there 
> is 'experienced'
> though.
>
> Recent studies in sub-adult Great White sharks suggest that their jaw bones 
> aren't strong enough
> for them to tackle large mammalian prey properly until they reach about 3m in 
> length:
>
> http://www.abc.net.au/science/articles/2010/12/02/3083105.htm
>
> This doesn't stop them from attempting such attacks; however they tend to 
> abort after just one
> exploratory bite. The danger to the shark isn't from the prey harming them in 
> defense, but in the
> shark's jaw muscles breaking its own jaw in the attempt to feed. I imagine a 
> juvenile tyrannosaurid
> might suffer a similar fate trying to subdue a well-armoured thyreophoran, 
> whereas a much older
> individual may have had the necessary equipment to power through that armour. 
> The potential
> dangerousness of the prey may have been a secondary concern.
>
> Also keep in mind that people tend to think of the huge 12m tyrannosaurs as 
> 'adults', and anything
> smaller as 'sub-adults'. If tyrannosaurs continued to grow throughout their 
> lifetime, as modern
> crocs do, then they may well have reached sexual maturity (ie. 'adulthood') 
> at much smaller sizes.
> The 12m long behemoths may have just been unusually long-lived individuals, 
> rather than
> representative of the normal adult state.
>
> --
> _____________________________________________________________
>
> Dann Pigdon
> Spatial Data Analyst Australian Dinosaurs
> Melbourne, Australia http://home.alphalink.com.au/~dannj
> _____________________________________________________________
>