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Re: Blood flow in Sauropods

>>A 8 metre long neck, 3 metres above the ground allows you to cut a 16 metre
>>wide swathe through the vegetation at a height of 3 metres of less without
>>overloading the blood circulation to the head associated with raising the
>>neck above the horizontal (of course these figures allow for maximum
>>lateral movement of the neck, but you get my drift). That is a blinking
>>good use for a long horizontal neck.
>Right. But LOWERING the neck below the horizontal to the ground creates the
>same kind of blood-pressure problem that raising it above the horizontal
>does, namely, how to bring the blood back up from the head. In order not to
>suffer blood-pressure problems, the head must be kept AT the level of the
>heart, neither above nor below it. And there is still the problem of bringing
>the blood back up from those 3-meter-tall legs. It seems indeed significant
>that in many tall vertebrates (elephants are exceptional, but they have
>trunks), part of their height comes from elongated legs, part from an
>elongated neck--as if striving to keep the heart midway between the extremes.
>Once the heart can generate enough blood pressure to get to the head "on
>high," it can also generate enough blood pressure to bring blood back from
>the legs below, and vice versa. This coincidentally dovetails nicely with the
>requirement that animals on tall legs still need some means of reaching
>ground level to drink, etc.

Yup, makes sence, but........

I am no great shakes on biophysics but surely we are talking about a
difference in an order of magnitude between a sauropod lowering its head 3
metres below the level ot the heart and lifting it 10 metres above the the
level of the heart by standing on its back legs.

Cheers, Paul