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On Wed, 24 Sep 2003, Mark Hallett wrote:

>> Forster's PALEOECOLOGICAL ANALYSIS OF THE VERTEBRATE
>> FAUNA OF THE MORRISON FORMATION (NMM, 2003, the study
>> concludes that in the Morrison there may have been a
>> lower abundance of vertebrate prey species in the
>> middle adult weight catagories (10-500 kg), due in
>> part from predation pressure by theropods in the
>>middle-large size ranges; this is similar to the
>> situation that Sinclair et al report in their
>>findings.

>On September 25,2003 John Bois wrote:
>Yes, it is.  And consider that larger species would spend considerable
>time (years?) passing through this range on their way to relative
>immunity.  Perhaps this was the preferred prey of said theropods--in 
>that view, adults in that range may have been eliminated by
>theropod opportunists.

In view of the most recent histological studies, the growth rate of 
medium-large dinosaurs would probably have been roughly equivalent to modern 
mammals of 
similar sizes. Although this, under the conditions of a modern East African 
ecology, would help get them out of the "vulnerability range" discussed in the 
Serengeti Study, they had to face much larger predators than those of Africa; 
these would have taken their toll of juveniles and sub-adults (like sauropods) 
a stituation that  juvenile-subadult rhinos and elephants didn't have to face.

--Mark Hallett