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RE: "running" elephants



In a message dated 4/3/3 11:45:55 AM Richard wrote:

<<To model the locomotion of a sauropod dinosaur on that of an elephant on
comparable top modelling the locomotion of an elephant from something
weighing about 300 kilos - a small horse, or a cow - which can do all sorts
of things elephants can't.>>

This comparison is not quite correct, because horses and cows have entirely 
different (running) legs from elephants. Juvenile and dwarf elephants have 
the same basic leg morphology and similar locomotary potential (inability to 
achieve a full suspended phase or ~25 km/h) as the big ones. The biggest 
sauropods had essentially elephantine legs and probably moved pretty much the 
same way and at similar speeds, especially since the leg muscles mass needed 
to move an animal at a given speed does not (contrary to recent claims) 
increase as a % of total mass as size increases. However, because giant 
sauropods had such enormous stride lengthes they may not have needed to shoft 
from a full walk to a semi-run to achieve 25 km/h. (Likewise, Triceratops may 
not have had to gallup to run at 40-50 km/h [a trot would do], a speed at 
which rhinos must gallup.) 

In the classic Wayne flick Hatari the pair of baby elephants are shown moving 
probably as fast as their wee legs can carry them, and they use the same 
basic ambling gait as the grownups. In particular frame by frame analysis 
shows that at least one foot is always in contact with the ground. There is 
no documentation that any elephant of any size can achieve even a trot or 
pace, much less a gallop.  

Someone brought up the issue of seriously overestimating mass of sauropods by 
failing to account for high sacs. Nein, nein, nein. Even in super pnuematic 
birds air-sacs drive specific gravity down to 70-75%, and no sauropod was 
anywhere near as filled with air spaces (long bones solid, sacs probably did 
not line the sides of the belly as in flying birds). Air sacs probably 
decreased sauropod density only 5-10% (this varied between species since 
primitive ones were less pneumatic than latter). Since an individual animal 
can normally vary in mass by 30% in a given year the air space issue is 
actually rather trivial. In any case I've long taken the issue into account 
in my estimates of sauropod mass. The one place it does make a big difference 
is in sauropod necks, where air-spaces may have made up as much as half the 
volume, so assuming a normal neck specific gravity will seriously 
overestimate neck mass and the effort needed to hold it up.
 
G Paul