Re: Lack of Running Giant Theropod Tracksâ

[Sim Koning <simkoning@msn.com>]

Augusto Haro Wrote:
 
>If it took the chest, good. But the torso is short and the legs wouldmove fast 
>in the worried >predator, so it would not be easy to miss thelegs. In 
>addition, the target is relatively small if >catchedfrontally.
 
I think it's worth noting that the head of a Triceratops is rather wedge 
shaped, which would reduce the likelihood of a straight on collision.
 
>legs. In addition, the target is relatively small if catchedfrontally. Anyway, 
>this would be >less of a problem in specimens withthe horns at 90Â from the 
>long axis of the skull. I >do not >trust muchin the capabilities of the small 
>nasal horn, overall because its baseis so close to >the point of the snout 
>weakened by the enlargement ofthe external nares.
 
The snout may not have been as weak as it seemed on the dinosaur documentary. I 
still maintain that the "experiment" was limited and rather flawed. For the 
sake of argument, I'll give it the benefit of the doubt however. I don't think 
the nasal horn would work as a 'primary weapon', but I imagine it would do some 
minor damage if it contacted flesh during a struggle. I'm guessing every little 
bit would help in a life and death struggle with a 6 ton super-predator.
 
>On the other hand, I was yesterday reading that the antelope whichbetter 
>defends itself from >dhole packs is one with short horns. Thissuggests to me 
>that relatively short horns are better >when dealingwith predators because 
>they permit more maneuvrability at close range.
 
Yes, but a T.rex was a far less maneuverable predator with much greater 
'firepower'. A single bite from a Tyrannosaurus rex may been crippling or 
fatal. Perhaps longer horns that could penetrate the heart and/or lungs with a 
single blow would have been more useful.
 
 
>it is posited that both the frilland horns are more likely of use in 
>intraspecific contest than >fordefense. The frill is also full of superficial 
>vessels (with apossible thermorregulatory >function), >and some bite directed 
>at it mayimply dangerous blood loss.
 
I very much agree that this was one of their primary functions, if not the 
primary function, but this does not mean that they could not have been very 
effective weapons for self defense too. We Humans use our legs primarily for 
locomotion, but they can also make for extremely effective weapons for self 
defense.
 
>I said it may be, but phylogenetic bracketing on living forms providesyou the 
>more parsimonious >hypotheses on the basis of the current evidence. More 
>parsimonious does not imply more certain. >Many birds hunt animals, not only 
>raptors, and in most of them no collective organization is >seen. Carnivorous 
>dinosaurs may have hunted in groups,or not - the last being more parsimonious 
>>to infer. That they can befound in close association may indicate 
>gregariousness(orpreservational >bias), as in crocs and many birds, not 
>necessarilycooperative hunting.
 
  I think since we now have rather strong evidence that some theropods employed 
some behavior that was staggeringly similar to some modern birds (such as 
nesting strategies) we are justified in speculating that many theropods may 
have had a similar degree of sociality. However I feel it's just as important 
to understand why it is various bird species are social, and some are not, 
before we start applying bird behavior to dinosaurs (for the sake of life 
restoration). For instance, we may not see many pack hunting birds of prey, but 
this may be due to a limited food supply and the need for relatively large 
hunting territories. There are some species of birds such as woodpeckers that 
work together in family groups to gather and store acorns. I know there is at 
least one species of raptor that works together to hunt rodents, but 
unfortunately I can't find a video or remember the name of the species. Of 
course most if not all raptors are also highly monogamous.   
 
>one crocodile, manyend up biting it and thus collaborate in killing it in 
>practice, butit does >not imply that the intention was to rely in 
>othercrocodilians, and may just be a case of intended >unique 
>predationcoinciding with the attempts of other crocs - perhaps the origin 
>ofcooperative >hunting and cognitive association of these occasions 
>withsuccess in killing by the individual >predators?).
 
Good point, I didn't think about that. Of course we do have modern caimans and 
birds forming creches, and we now see this behavior recorded in dinosaur 
fossils, so using phylogenetic bracketing to infer behavior certainly has some 
merit. I also remember seeing alligators working together to form a living fish 
trap somewhere... 
 
 
>Your example of the bats indicates the dangers of inferring from theRecent 
>only. But, in lack of >more conclusive evidence either way,parsimony is all 
>you have.
 
I think it depends on what behavior we are talking about. Many once thought it 
was more parsimonious to apply scales to small dinosaurs, which ignored the 
probability that they were likely warm-blooded animals, and that mammals have 
hair that evolved for insulation, so dinosaurs may have done the same. I could 
make the same argument in regards to social hunting: we don't see birds of prey 
hunting in packs, but they are flying animals, and predatory dinosaurs may have 
filled niches more analogous to modern predatory mammals, and so may have had 
analogous behavioral adaptations.  
 
>In any case, it seems that theropods mostlyate young, as many Recent 
>predators, and thus would >not have requiredgrupal hunting.
 
This could also mean that the young may have engaged in group hunting as well. 
Heck, as I suggested with T. rex, for all we know the young may have been pack 
hunters, while the breeding adults may have been solitary or monogamous. This 
would be an intermediate between the creche forming of crocs and other 
dinosaurs, and the monogamous behavior of most modern birds.   
 
 
>Whether the adult ceratopsians did or did not put mucheffort in the defense of 
>their youngs is >unknown. 
 
There was the Psitticosaurus that was found dead with a creche though.
 
 
>And, regarding the question "why animals hunt in packs?" as being morehelpful 
>than invoking >phylogenetic bracketing, I do not see why it isof more 
>relevance when dealing with the behaviour >of the T. rex. 
 
>Youmay answer that because the prey is difficult to take individually,but 
>there is the >alternative way to take: do not attack the dangerousprey.
 
 Triceratops was the most abundant herbivore in a Tyrannosaurus's ecosystem, 
and we have evidence of an actual battle between the two species; I would say 
the chances are pretty good that they attacked and killed Triceratops quite 
often. Many pack hunting predators will grip the head/face of their prey while 
others go after the throat of guts. The bitten off horn on the Triceratops may 
be evidence of very similar behavior among T. rex.
 
 
Simeon Koning