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Re: Sloping terrain Re: Woman against Abelisaur

It's also worth noting that talking about "theropods" and "sauropods"
is a bit like arguing over whether carnivorans or artiodactyls are
better adapted for swamps - there isn't a one-size-fits-all answer.
Some theropods have proportionately shorter toes than others.
Likewise, just in the Morrison the similarly sized Apatosaurus and
Camarasaurus show quite a difference in how compact the manus is (with
apato hands being less compact and more laterally splayed).  There are
probably significant differences in the hind feet (Apatosaurus is
certainly more massive) but how different it is also depends on how
you reconstruct the biomechanics of the ankle/foot, so I'll leave that
for another time.

In short, without specifying which predator/prey relationship we are
talking about we're engaging in a very imprecise discussion.


On Mon, Jul 25, 2011 at 11:49 AM, Habib, Michael <MHabib@chatham.edu> wrote:
> On Jul 25, 2011, at 12:20 PM, Don Ohmes wrote:
>> The intuitive 21st century perceptions just do not work when examined
>> closely.
> That depends on which set of perceptions we're looking at.  If by "21st 
> century perceptions" you mean the blanket concept that sauropods were always 
> at a disadvantage on compliant terrain compared to theropods, then yes - that 
> 21st century perception is overly simplistic.  There are conditions in which 
> we can at least show, theoretically, that sauropods should have moved with 
> greater efficiency than theropods on compliant terrain (specifically, terrain 
> with an extremely soft layer over a harder one).  However, to suggest that as 
> a result sauropods must have frequented such terrain is another supposition 
> altogether.  The specific substrate circumstance that provides the tradeoff 
> you're suggesting would still be a difficult surface for a sauropod to move 
> in (just not as difficult as shorter animals).  Those substrates conditions 
> are also likely to be localized, and provide insufficient food resources.
> More to the point, we don't see any specific adaptations in sauropods to 
> moving on compliant terrain - by simple virtue of being large, they could 
> wade through semi-fluid substrates more easily than small animals, but that's 
> really a simple matter of height and mass.  If sauropods were habitual swamp 
> dwellers, I would expect them to have feet adapted to such conditions (which 
> they don't) and the ability to maneuver in cluttered environments (which 
> seems unlikely).  Furthermore, we should find sauropods regularly preserved 
> in swamp-like conditions *without* evidence for miring.  To take your earlier 
> analogy: yes, penguins drown - but they also get eaten by sharks, starve to 
> death, and die of disease.  Because penguins are primarily marine, they tend 
> to show up in marine deposits regardless of cause of death.  If sauropods 
> were habitual swamp specialists, then we should find their remains in those 
> conditions on a regular basis, in a non-mired stance.  If they keep showing 
> up mired to death, then that seems inconsistent with swamp specialization.
> Of course, the caveat to all this is that I know from the previous 
> conversations that Don is looking for a predator escape strategy, which is 
> reasonable if one expects giant theropods to have been munching on big 
> sauropods.  Personally, I think the baby-killer hypothesis for most big 
> theropods is more plausible, so I don't really worry too much about finding 
> some way to save the big herbivores as adults.
> Cheers,
> --Mike H.

Scott Hartman
Scientific Advisor/Technical Illustrator
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website: www.skeletaldrawing.com
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