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Sauropod necks and metabolics



Carrying a sauropod neck horizontally would be no more difficult than
carrying a sauropod tail horizontally, so let's drop the unresolvab
le speculation and look at the articulation of the vertebrae at the neck
base. Diplodicid necks were horizontal, but these animals ofen reared up. In
the Chinese sauropods and camarasaurs the neck is kinked upwards at the base,
so the head was held high. Neck base is not completely known in brachiosaurs,
but high shoulders imply erect necks.

All sauropods therefore had to have blood pressures much higher than in any
reptile, and probably matching or exceeding that of giraffes (200 mmHg). 

Whether they had a single oversized heart (which would require implau
sibly high pressures up to 700 mmHg), or a large main heart and extra neck
hearts (only 200 mmHg needed), the 



work that had to be done by a 100 tonne sauropod's heart to pump blood all
the way up to its brain, and to oxygenate 45 tonnes of skeletal mus
cles, would have equalled the entire metabolic rate of an elephant! (The work
done by a reptilian sauropod's heart would be only as much as an elephant's
heart, not nearly enough to power a w
hale sized beast in 1 G.) Because the lungs, liver, kidneys, digestive tract
of the sauropod would have to work hard to support the huge hard working
heart, the total metab
olic rate of a 100 tonne sauropod would have been similar to that of a 100
tonne whale. It is probably impossible for true reptiles to exceed 1 tonne on
land, they cannot produce enough power to live in 1 G - which is why giant
land  mammals are bigger than the biggest1 tonne extinct monitors and
tortoises (See 1994 DinoFest, Rosenberg & Wolberg ed, Paleo Soc, Dept Geol
Sci, Uni Tenn., Knoxville 37996-1410 $30 for a preliminary outline of these
ideas by Paul and Leahy.)   

And spare me the nonsense about giant endotherms overheating. The world's
biggest elephants live in the Namib desert, and they have been filmed
regularly walking across barren lands (nearest shade 20 miles way) at noon
with air temps over 100 F! They do not die. As those who study the extensive
literature on big mammal thermoregulation know, g
iants can store all their body heat during hot days, and dump it at night. 

Among dinos large and small, only some early forms of relatively small,
rather reptile-like limb musculatures (marasuchians, herre
rasaurs, prosauropods) show evidence of metabolics rates transitional to
reptiles and birds. All other dinosaurs seem to have large, aerobically
capable musculatures and high blood pressures indicative of avian-mammalian
metabolic rates - however nonpolar dinos may have lacked the thermoregulatory
controls of birds and mammals. There is no evidence that any dinosaur had a
truly reptilian metabolic system.

GSPaul