Re: Sauropod Energetics (Peristaltic pumps for arteries?)

[Guy Leahy <xrciseguy@sbcglobal.net>]

If Kent's reconstructions are correct, the neutral
head position in Brachiosaurus would have been 6-7 m
above ground, similar to the estimated head/ground
distance in indricotheres.  Although it may be
coincidence, it's interesting to note the heart/head
distance in indricotheres is similar to large
giraffes.  Perhaps a heart/head distance of ~2 m
represents a physiological constraint for mammalian
cardiovascular systems to supply blood to the brain?

It's reasonable to infer that indricotheres possessed
a more or less typical mammalian cardiovascular
system, so a heart/ground distance of 6-7 m would
appear to have been supportable by such a system.  If
the cardiovascular system in sauropods was more
similar to birds than mammals, somewhat higher total
blood columns might be possible.  For example, mammal
hearts average ~0.6% of body mass, whereas in birds
the heart is typically ~1.0% of body mass.  Therefore,
a 40 tonne brachiosaur would have had a heart mass of
~400 kg, approximately twice the size of an equivalent
sized whale.  

Guy Leahy

--- Allan Edels <edels@msn.com> wrote:

> Of some note in this discussion:
> 
> Indricotherium. (2006).
> Encyclopædia Britannica.
> Retrieved January 25, 2006, from Encyclopædia
> Britannica Premium Service. 
> http://www.britannica.com/eb/article?tocId=9012066
> 
> "Indricotherium, formerly Baluchitherium, genus of
> giant browsing 
> perissodactyls found as fossils in Asian deposits of
> the Late Oligocene and 
> Early Miocene epochs (30 to 16.6 million years ago).
> The indricotherium, 
> which was related to the modern rhinoceros but was
> hornless, was the largest 
> land mammal that ever existed. It stood about 5.5 m
> (18 feet) high at the 
> shoulder, was 8 m (26 feet) long, and weighed an
> estimated 30 tons, which is 
> more than four times the weight of the modern
> elephant. Its skull, small in 
> proportion to its body, was more than 1.2 m (4 feet)
> in length. 
> Indricotherium had relatively long front legs and a
> long neck; thus, it was 
> probably able to browse on the leaves and branches
> of trees. Its limbs were 
> massive and strongly constructed."
> 
> Note that _Indricotherium_'s SHOULDER was the height
> of the largest 
> giraffe's entire body!  It had a long neck and a
> large skull.  (In 
> comparision to the giraffe or the sauropod, neither
> of which had a large 
> skull).  My estimate for the height of the beast
> (its former name, 
> _Baluchitherium_, means beast from Baluchistan), is
> around 6.75 meters.  
> (Note also, that a possibile synonym for
> _Indricotherium_ is 
> _Paraceratherium_).  The heart-head distance was
> probably around 2 meters, 
> and I image that its blood pressure would be even
> higher than extant 
> giraffes.
> 
> The article in Wikipedia that Guy referenced, also
> describes some giraffe 
> adaptations for handling the extremes in BP that
> giraffes experience.  I 
> gonna guess that _Indricotherium_ and sauropods had
> vey similar (or even 
> more extreme) adaptations.
> 
> Allan Edels