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Saturday, 13 July 2013

The Problems with Plesiosaur Necks

I have been catching a lot of flack lately from people who have not read my earlier remarks about Plesiosaur necks and who therefore rely upon summaries made by somebody else on the subject. Why people have to make such an issue of this is beyond me.


Plesiosaurs had all sorts of different necks of different anatomy, different lengths and different flexibility. That is the outcome when you have any sort of adaptive radiation. It is absurd to make blanket statements that all Plesiosaurs had necks that were alike even if some necks might have been longer than others or less flexible than others (To select only two variables)

This was one of the Plesiosaur classification trees used by Darren Naish recently. It does not continue the Cryptoclididae forward from the Jurassic to the end of the Cretaceous as other authors do (as the Wikipedia entry also has it), leaving several taxa traditionally included in that family as orphans now. Unfortunately that does include our suspected genus of PostCretaceouis survivors: provisionally, though, I continue to consider them to be Cryptoclidids or whatever name the successor family is given. They are not Elasmosaurs (More on this later)

The argument goes that Plesiosaurs had necks which they kept down in the water and could not hoist up into the air to form stretched-S or Periscope formations so commonly shown in the older reconstructions, like in this public-domain image example:

Actually going by the skeleton shown in this Russian illustration, I estimate that the vertebrae in the neck had enough wiggle room to assume any positions within the range as indicated, and that the body was substantial enough to be able to support the neck in these positions. (Brown is the original and the black lines are my extrapolations translating the estimates of the more liberal experts, The Russians I think would allow these parameters, I think.  In American and European scientists it is the more conservative element that denies this degree of flexibility in Plesiosaurian necks.
Several Fossil finds had necks that could assume positions along these lines: some fossils are FOUND with their necks indicating a greater flexibility than some of the skeptics allow. Almost all of these are Plesiosaurs that had necks that were less than half the total length and substantial torsos.



The following is a direct drawing of the vertical upcurl on a relatively short Plesiosaur neck. The upcurl stats to become noticeable about ten vertebrae forward of the body. Some Plesiosaurs had 75 neck vertebrae. Such a neck should be well over twice as flexible in all planes as this neck (all other factors being the same) and if this neck were to turn forward instead of back at the top, it would be able to crudely form the "stretched-S" posture. (And from the orientation of the vertebrae this is definitely in the vertical plane and not the horizontal)
Some Plesiosaur skeleton mounts continue to beerected and displayed as showing the traditional degree of Plesiosaur neck ability. If nothing else, this goes to show that not ALL experts go along with the idea that the necks could not be fitted into those patterns, and that this remains a matter of controversy. The following image is from

Below is a Canadian one. Several museum mounts indicate the neck falling naturally into a shallow S-curve  in the vertical plane: the Canadian one shows this and so do many American ones. 

Elasmosaurus scale, also shows neck in shallow vertical S-curve
The kicking is really over the very long necks of the Elasmosaurs such as Elasmosaurus (below)

In this case we also have a fossil showing the neck in a definitely snaky wiggle pose. Apart from the stomach being burst open in this specimen, most of the body was still mostly articulated:

From this fossil alone, t seems to me that Elasmosaur necks would have just about the flexibility indicated in this chart from a Scientific paper) which I have been criticized for running before:
However this is horizontal movement. The charge was also made that the vertebral spines on the Elasmosaur neck were too tall to allow for much vertical movement. let's check that part. Here is a replica of an Elasmosaur skeleton being built:
And here is a section of the neck. It looks to me as if there is plenty of free space all around to allow flexibility in all planes (all other possible factors excluded since we are only talking neural spines)

Now why should Scientists be insisting Elasmosaur necks were clumsy and could not be lifted out of the water? The answer it seems is more physics rather than anatomy.
When you are talking about an animal that has a neck that makes up more than half the length, there is not enough muscular strength in the body to hold the neck up out of the water. Its a question of leverage and the fulcrum is placed way too far back.

 This ignores the possibility that the neck may be bent in the middle. However this is the practical reason why Elasmosaurs were stated to have necks which could not be held up out of the water. I have no problems with that.

We are not now and never have been talking in terms of the Elasmosaurs with extremely long necks!
All we have ever done (from Gosse on) is to suggest that we are dealing with a very large kind of Plesiosaur with a moderately long neck (less than twenty feet ): "Essentially a Plesiosaurus with the colossal magnitude of a Pliosaur" as Philip Gosse said in 1860

Romance of Natural History on Googlebooks


  1. Who are the "more liberal experts on plesiosaur anatomy" mentioned in this article?

  2. You must remember that historically speaking, that was the default view and the majority of experts on Plesiosaurs have held that opinion. The history of the various controversies about Plesiosaurs, their anatomy and how they worked is at Scott Mardis' guest blog

    And almost everything about Plesiosaurs has been controversial in the past or remains controversial to the present. WE are not certain how they swam, how their flippers worked, whether or not their spines bowed up and down as they swam (which is a legitimate theory based on real Plesiosaur anatomy), let alone the question of how flexible the neck was in different species, genera and/or families. There is virtually no consensus of opinion on anything concerning Plesiosaurs. Therefore I find your repeated assertions on the topic to be merely poorly informed and chauvinistic to your own favourite theorists. To a fault. And once again, it is a trait of pseudoscientists to seek the answers by deferring to a higher authority. If you're thinking of jumping up and saying "MY authority trumps YOUR authority," forget it. Among other things I have noticed, you don't play fair.

  3. Is figure 9 supposed to show an actual plesiosaur fossil with its neck articulated into that position?

  4. Figure 9 is indeed directly cut out of a scientific illustration of an actual Plesiosaur fossil, yes. Now go sit in the corner and eat your words like a nice little boy.

  5. I'd be cautious on using museum mounts as evidence. After all, dinosaurs used to be mounted with their tails dragging on the ground even though it was physically impossible. And I know you're gonna say that in this case the fossils back the mounts up, but still, when it come to museum mounts it's best to be cautious.
    Best regards,
    Tyler Stone

  6. True enough but the fact about museum mounts is that they demonstrate that The neck vertebrae can be articulated naturally that way and not come across as visibly jarring or disarticulated


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