That Plesiosaur neck

[andrewsaurus rex]

i've always been curious about the long necks of Plesiosaurs.  Especially the really long ones on Elasmosaurus and Albertonectes.  The fact that the necks were tending to evolve longer, up to the extinction, implies there was a very purposeful use for them.

But what?  And how on earth did they avoid being decapitated by every predator in the Cretaceous sea?

I've read lots of theories, but none of them quite make sense to me.  One I just finished reading suggested that Elasmosaurus et al fed along the bottom, filtering out crustaceans with their teeth.  Ok....but why do you need a long neck to do that?  Elasmosaur necks could be 5 feet long and they could still feed that way....you don't need a 23 foot long neck for that.

Another puzzle is why have so many vertebrae in the neck, up to 75 in the case of Albertonectes, but then have a stiff neck?  If stiffness was needed, then why would the vertebrae not just evolve longer, as in the case of Tanystropheus, but instead they increased in number, for seemingly no purpose.

As to predation, a while ago I read a very interesting idea that suggested that Plesiosaurs may have been able to generate an electric current, like an electric eel does today.  This would have been useful for both eating, by stunning prey and then casually scooping them up and for defense by zapping any would be predator that came along.  While an imaginative idea, in the absence of any evidence I think it's dubious.  My own personal feeling is that Plesiosaurs may have been fowl tasting or even poisonous and as a result predators gave them a wide birth. Plesiosaurs may even have had stripes or other warning markings on their bodies to warn off any would be hungry adversary.  But again, this is just pure speculation.

I would like to hear (read) thoughts and ideas on any of these issues...

[Halichoeres]

Perhaps you are aware that the forum's founder has written a book on the subject? https://plesiosauria.com/the-plesiosaurs-neck-book-pre-order/

[DinoToyForum]

Perhaps you are aware that the forum's founder has written a book on the subject? https://plesiosauria.com/the-plesiosaurs-neck-book-pre-order/

Yes, and there are just two weeks to go until it is released!

[andrewsaurus rex]

did not know that.   Very cool.. 

[stargatedalek]

Long necks make for good torque, stiffness aside. They were well capable of doing some serious damage if they had to, and the threat of an extremely painful bite, especially if it were coupled with a giant flashy neck, may have been enough to discourage most predators, or at least counteract any potential vulnerability the neck presented.