Comments on: Of Barosaurus and Blood Pressure

By: Andrew_Raybould

Andrew_Raybould — Sun, 17 Mar 2013 00:14:22 +0000

Like several other commenters, I thought of the valves we have in our veins – could not something similar have evolved in sauropods’ carotid arteries? With periodic contraction, the artery would function as a pump.

Furthermore, if the artery were bound to the esophagus, perhaps that periodic contraction could have been driven by the action of swallowing. I am thinking of the artery being squeezed either by an expansion of the esophagus as a food bolus passes by, or by the circular bands of muscle that contract the esophagus in peristalsis, if the artery passed through or inside those bands.

Alternatively, though less elegantly, perhaps sauropods periodically charged their heads with blood by lowering them, and maintained pressure while the head was raised by closing sphincters in the arteries and veins at the base of the neck. Given that some whales can go for an hour or more between breaths, perhaps a sauropod could go for tens of minutes between cranial blood changes?

Such sphincters could also control the increase in cranial pressure when the head was lowered – just restrict the arteries and open up the veins. I can think of a mechanism which works that way to give variable pressure within a human organ…

By: tony

tony — Wed, 06 Mar 2013 12:07:48 +0000

Would it be possible for the arteries to be made of a smooth muscle like an intestine? This would allow for blood to be pushed around by the arteries themselves as a booster mechanism which would relieve stress on the heart. Smooth muscle could be triggered by the heartbeat, and it could also regulate pressure when the head was lowered. This would also be different than little pumping stations in the neck. Would this get by all the issues of having a huge body?

By: Tyler

Tyler — Sun, 03 Mar 2013 20:45:05 +0000

Brian, does being warm-blooded or cold-blooded matter for something like blood pressure? I remember reading a theory that claimed sauropods had a more warm-blooded body chemistry in their formative years. This was considered to be an explanation of their rapid growth. Then, once they were of a comfortable and predator-proof size, their internal chemistry changed to be more like a cold-blooded animal. Is there any credence to this theory, and could it explain how the most massive adult animals could keep the blood moving?

By: PalMD

PalMD — Sun, 03 Mar 2013 14:38:15 +0000

Human mammals also give us clues. Our leg muscles help pump blood back to the heart. I wouldn’t be surprised if that sort of arrangement was one of perhaps many mechanisms that evolved with long necks. All sorts of anatomic quirks may have been coopted.

By: Austin

Austin — Sun, 03 Mar 2013 05:11:26 +0000

I grew up reading and hearing that dinosaurs had a second brain at the base of their tails. This was treated as common knowledge. A lot of books I read as a kid also said that larger dinosaurs (sauropods, specifically) had to live in the water because they were so bulky.

I hope kids today aren’t still hearing this stuff.

By: PabloK

PabloK — Sat, 02 Mar 2013 16:11:41 +0000

Is the thinking too linear? Brain storming this problem, could we think of much thinner blood?
How about a design callung for much less need of blood to begin with?

Also, on the neck position, the rationale for a giraffe-like elevated stance makes sense because there is an evolutionary advantage in the higher reach. What would be thenone for a hugely long horizontal neck?

By: Ashley Metcalfe

Ashley Metcalfe — Sat, 02 Mar 2013 01:27:45 +0000

Convincing stuff from Christian that Euhelopus could have raised its neck without causing any significant extra stress on the vertebrae and benefitted energetically at the same time. In your opinion Brian, what research needs to be done to prove how the neck was positioned at rest?

Very much appreciated the Monty Python reference as well. “This theory…”

By: Jim Kirkland

Jim Kirkland — Sat, 02 Mar 2013 00:51:13 +0000

In 1991, I was thrilled to see Discover magazine chose our announcement of Utahraptor as one of the top stories in science for that year. However, I was sorely let down when I saw the trash on the facing page. A tribute to the publication of an off the cuff theory that Barasaurus must have had multiple hearts.

This is the reference: Choy DSJ, Altman P. The cardiovascular system of Barosaurus: an educated guess. Lancet 1992; 340: 534-536. The bigger a heart is, the slower it beats. Therefore the blood would run back to the heart before it reached the brain. Because of that, there’s another theory that the Barosaurus had 8 hearts: Two in the chest and three pairs in the neck, which all worked together.
Occam’s Razor; it ain’t!

Much simpler to develop valves in the veins and arteries to control blood flow and pressure as in a giraffe.

By: Michael Barton

Michael Barton — Sat, 02 Mar 2013 00:09:46 +0000

That’s so cool that he responded with a follow-up question!