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Re: Sauropod ONP...and energetics



One potential problem with rearing up (primarily in
diplodocoids and Mamenchisaurus)is the extremely large
heart-head vertical distances might be physiolgically
constrained by difficulties in producing sufficient
blood pressure to reach the head, as disussed in the
article below:

http://www.journals.royalsoc.ac.uk/media/1lbfddakxn3xwhe1fl1y/contributions/k/b/b/w/kbbwl6ee805dk8vx.pdf

The heart-head distance in a rearing pose would have
exceeded 10 metres for some sauropods.  It's unclear
from analogies with modern taxa whether the blood
pressures needed to perfuse the brain under such
circumstances are physiologically possible,
considering what we know about avian/mammalian cardiac
performance. There might also be alternative selection
pressures for long necks other than feeding, as this
article below suggests:

http://links.jstor.org/sici?sici=0003-0147(199611)148%3A5%3C771%3AWBANSS%3E2.0.CO%3B2-A#abstract

In addition, the relatively short forelimbs of
diplodocoids could be interpreted as an adaptation to
low browsing, a food source which might have been more
difficult for longer-armed taxa such as Brachiosaurus
to utilize.  According to Kent's research, Apatosaurus
and Diplodocus would have been able to access plants
which were 5-6 m and ~4 m high respectively, so their
capacity to feed fairly high up was still available. 
Like giraffes, they may have used taller foliage
during the dry season, and lower browse during the wet
season.

Guy Leahy



--- dinoboygraphics@aol.com wrote:

> But ratites have necks that are just long enough to
> reach the ground in 
> a tiny little arc, exactly what you would expect
> (energetically) from a 
> primary grazer.  Regardless of neck posture,
> Camarasaurus is a better 
> model for a grazing dinosaur than diplodocids are
> (although the neck is 
> still too long).  Dicreaosaurs are what a primary
> grazing diplodocoid 
> should look like (Brachytrachelopan any one?).  If
> diplodocids where 
> primary grazers, we need to explain why they don't
> all look like 
> dicraeosaurs.
> 
> As for reachinginto forests (different post) ...why
> not just rear up 
> then?  You would be able to exloit a far more
> effective browsing 
> envelope than sticking your neck into dense forest
> from the periphery, 
> where the trees would prevent you from lateral
> excursion of the neck.
> 
> Scott Hartman
> Science Director
> Wyoming Dinosaur Center
> 110 Carter Ranch Rd.
> Thermopolis, WY 82443
> (800) 455-3466 ext. 230
> Cell: (307) 921-8333
> 
> www.skeletaldrawing.com