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The mystery of plesiosaurs' long necks


Claire.

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Why the Long Neck?

Floppy plesiosaurs have been out of style for a few decades now. Even though there hasn’t been a Plesiosaur Renaissance to match the dinosaur equivalent of the late 20th century, expert anatomists have nevertheless given plesiosaurs stiffer, straight necks that operated in coordination with the rest of the body rather than as independent, snaky appendages that could dart one way while the body was moving another.

But this has only raised new questions, ranging from how long-necked plesiosaurs were able to catch their food to how a ludicrously-proportioned animal like Elasmosaurus could manage to swim away quickly from predators without giving itself a literal pain in the neck. The answer requires a rethink of how these famous marine reptiles behaved.

Read more: Scientific American

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I well understand that the old depictions have been rendered inaccurate now, but aesthetically I liked Mesozoic reptiles much better when they looked like Charles Knight's paintings. I want my Brachiosauras in a swamp Burian style, and I want my Elasmosaurs with twisty bendy necks.  (I prefer the new Mosasaurs though) 

http://dino.lindahall.org/img/bur1m.jpg Wrong but very evocative. 

I'm happy to compromise though, can't they reproduce them near a swamp? Sort of looking at it wistfully, maybe looking a bit moist? 

On a serious note I was very, very surprised to come across a paper discussed on a blog I follow (The Evolving Placenta) and that the author (of the paper not the blog) 'Seymour goes so far to suggest that long-necked sauropods like Diplodocus were aquatic, floating on the surface of the water and lowering their heads to browse on vegetation. Abdominal air sacs would have helped it to float'.

The next paragraph says, 

Sauropods are generally regarded as terrestial because of skeletal features, but perhaps they retained these because they needed to go on land to lay their eggs!

http://placentalevolution.blogspot.co.uk/search?updated-min=2017-01-01T00:00:00%2B01:00&updated-max=2018-01-01T00:00:00%2B01:00&max-results=4

But I'm not sure if this is proposed in the paper or whether it's the blogger, Anthony Michael Carter, having a bit of a laugh at the idea. 

As much as I like this blog, I'm a little surprised to see this Dinocephalosaurus reconstruction being used https://4.bp.blogspot.com/-XZXt6f6dYyE/WMKwJ2mPiQI/AAAAAAAABJE/0aO9t247GGUFV6tv2-MRrYWoRtY7aLtWQCLcB/s320/Dinocephalosaurus-embryo-3.jpg

I know next to nothing about this, but was under the impression that the Nigel Marvin style fully aquatic version had given way to a heron like hunter as per Mark Whitton. http://markwitton-com.blogspot.co.uk/2015_12_01_archive.html

That's another recent reconstruction that I much, much prefer. 

 

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50 minutes ago, oldrover said:

I well understand that the old depictions have been rendered inaccurate now, but aesthetically I liked Mesozoic reptiles much better when they looked like Charles Knight's paintings. I want my Brachiosauras in a swamp Burian style, and I want my Elasmosaurs with twisty bendy necks.  (I prefer the new Mosasaurs though) 

Heretic! :lol: In all seriousness though, I too miss the classic paleoart from the likes of Knight, Burian, and Zallinger. I wish more modern paleoartists would emulate their style, just with up to date dinosaurs. I think the closest you can get today would be Josef Moravec or Jan Sovak (both Czechs like Burian).

53 minutes ago, oldrover said:

On a serious note I was very, very surprised to come across a paper discussed on a blog I follow (The Evolving Placenta) and that the author (of the paper not the blog) 'Seymour goes so far to suggest that long-necked sauropods like Diplodocus were aquatic, floating on the surface of the water and lowering their heads to browse on vegetation. Abdominal air sacs would have helped it to float'.

Do you know what paper that was? That pre-Renaissance type thinking reminds me a lot of Brian Ford's wacky hypotheses: https://blogs.scientificamerican.com/tetrapod-zoology/brian-j-ford-s-aquatic-dinosaurs-2014-edition/

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11 minutes ago, Carnivorfox said:

 I wish more modern paleoartists would emulate their style, just with up to date dinosaurs. I think the closest you can get today would be Josef Moravec or Jan Sovak (both Czechs like Burian).

Yes, that's much more like it. Particularly Jan Sovak. I did note the presence of a kiwi feathered terror bird there though. Now I really like their new make over. 

The paper is here http://physiologyonline.physiology.org/content/31/6/430 I haven't read it, I've lost my Athens loggin. What I know is from the blog discussion, and that Seymour seems to have some concern about the Mean Arterial Pressure (MAP) would be crazily high if it maintained its BP with a raised head. Now, I don't know much about a sauropod's cardiovascular system, but humans I do understand, and a MAP of 700mmhg would blow any blood vessel to pieces like a stick of dynamite in a Coke can.

In us average healthy MAP is about 65-90mmhg. Go much more than that and you've got issues, double the upper figure and you're in immediate and serious danger. Obviously, the main vessels in a sauropod are going to be huge by human comparison, but anything that branched off that to supply an organ, or in fact any of the non major vessels would still fail under that much pressure. But giraffes manage to maintain a MAP of around 200mmhg, and they need to get the blood about 17' off the ground. I believe they address the problem of how to regulate pressure between a lowered and raised head by constricting the vessels supplying the head to maintain BP when raising it, the same principle we use with vassopressors to support patients who are dangerously hypotensive. Surely, sauropods would have some similar mechanism to support their MAP without the need for a huge and stupidly overpowered heart? But I haven't read the paper. Also what's he using to estimate the amount of blood needed by a sauropod with a raised head? 

But didn't Bakker address this years ago? Isn't this one of the thing that began to lead people into the 'Dinosaur Renaissance'? 

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Also, if as the blog states, Seymour thinks that they couldn't have raised their necks for that reason, then how the hell were they going to lower them? It'd be the same thing without some sort of system for regulating the flow they're little heads would still explode from a crazily high BP. 

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1 hour ago, oldrover said:

Also, if as the blog states, Seymour thinks that they couldn't have raised their necks for that reason, then how the hell were they going to lower them? It'd be the same thing without some sort of system for regulating the flow they're little heads would still explode from a crazily high BP. 

Well, that would explain why they went extinct. 

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20 hours ago, Parsec said:

Well, that would explain why they went extinct. 

I think another possibility even if they could regulate blood flow may have been if the water was choppy it could, through acting on the weight of the body, have driven their little heads into the mud. After all, they did come to a bit of point both ends. 

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