Sea Serpent Reconstructions and the problem of the Longnecks' Necks

My original statement made about Longnecks was made back in 2009 under the heading

 "TWO Long-necked sea creatures"

on the CFZ blog:
 http://forteanzoology.blogspot.com/2009/11/dale-drinnon-two-long-necked-sea.html

"This concerns two different long-necked animals reported as Sea-Serpents. The first is the Long-necked sea lion such as reported off the Island of Hoy in 1918 and the other is the larger more Plesiosaurian creature more commonly seen.




Parsons_1751_long-necked_seal

This (Top) would be the same type as the Hoy Island SS of 1918. It is a rather poor drawing of an exaggerated but fundamentally normal sealion type.

"There are more samples from the group Frontiers-of-Zoology. The Kivik Stone is in the files and has this description:

'Original for some of Holiday's creature drawings: showing a possible Scandinavian long-necked sea lion of unknown type.'

"However, that is not the only or even the more important of the long-necked Sea-Serpents. Tim Dinsdale's illustration from Monster Hunt shows one of the larger, longer-necked, smaller-headed, tailed creatures hunting seals (which it evidently kills but does not eat, and when they are said to kill human beings the same thing is said again).

'This is incidentally one of three such plain representations of a Plesiosaurian tailed creature seen from above that Heuvelmans must have known about: two other examples were in Sanderson's archives. A later and better-known example was the Plesiosaurian creature seen by the research submarine Alvin in the tongue-of-the-sea, off Grand Bahama.

"The larger collage [Lost by the CFZ in the original printing] is also from the files of the group and collects together several pre-contact representations of Plesiosaur-shaped creatures, from prehistoric rock art up until 'Primitive' art in more recent times. This is only a sample from the groups' photo albums. Specifically Plesiosaurian anatomy shows in several cases: sometimes the specific skeletal structure of the paddles and limb girdles is shown, sometimes even the characteristic Euryapsid openings at the back of the skull are clearly intended (Snakes have nothing like that)

greek-sea-serpent2, compared to Plesiosaur
E=Euuyapsid opening behind the eye, O=Eye socket, N=Nostrils, all in their proper places

"I presume that both types can wander inland but they do not make a career of it: and the two areas in specific where the long-necked seals wander inland are Ireland (Shannon River system especially) and Australia (where they are sometimes called Bunyips. Not the only things called Bunyips, either).

Grant Nessie sighting compared to the hypothetical long-necked sealion (above right)
And even more so for the Plesiosaur at bottom (Cryptoclidus from Walking with Dinosaurs)

 

"And personally I prefer maintaining the proposed scientific names of Megalotaria for the sea lion and Megophias for the more typical long-necked (and tailed) sea-serpent. My colleague Charles Paxton is, however, strongly opposed to the suggestion."

Megophias was the name given to the American Sea-Serpent in an unrecognizable description by Rafinesque but because of that Anton C Oudemans insisted it must be retained as the proper name when he wrote his own book , The Great Sea-Serpent (1892), and for which he made the following reconstruction of it. Beneath Oudemans' version are the reconsteuctions of Ivan Sanderson and then Tim Dinsdale from Loch Ness Monster (1960), with the humps on the back removed (As per his remark "They might as well have been left off")

 

These reconstructions are entirely comparable and the general feeling after Oudemans has been that he allowed too great a length for the tail. Sanderson allowed about equal thirds of the total length for the head-neck, body and tail, but later versions (and his own later versions) have tended to allow even less for the tail.

Tim Dinsdale states the data on the neck in Loch Ness Monster page 19: "Taking into account the angle at which the neck is held or the graceful arch when motionless in the water, and the consistent reference to a height of 5-6 feet above the water, total length of the neck must be 9 or 10 feet [With the neck at an angle, travelling forward at speed, and the cylindrical forepart of the neck evenly a foot thick according to the drawing on the opposing page,], and in view of its sinuous fexible movements it must be extremely muscular; a solid pillar of muscle springing from a tremendous breadth of shoulder, 2 or 3 feet thick at its base perhaps, then tapering down suddenly before continuing out to the head with an almost parallel thickness [Oudemans' reconstruction shows this also- DD] It is a very remarkable neck and if people are to be believed it is quite unlike that of any known living species- fish, mammal or reptile, and there is no doubt that irrefutable proof of its existence will provide a very tough morsel for scientists to chew upon"

 

My contention is that it is impossible for a mammal to have a neck that fits these specifications

Below is a diagram comparing Heuvelmans' model to Oudemans' (minus the tail) in order to point out the problem of a Long-necked mammal: Placental mammals including seals have  only the standard 7 neck bones (Seven vertebrae).

Dimensions of sample Sea serpents from Oudemans' chart page 492:
A) Length of head, 1 foot; length of neck 6 feet; length of trunk 7 1/2 feet: breadth of head,8 inches: thickness of neck , 4/9 feet, Dale says 6 inches and be done with it; Oudemans total is 28 feet, Dale's total is 20 feet.
B) Length of head, 2 feet; length of neck 11 2/3 feet, Dale says 12-13 feet; Length of trunk 15 feet; Breadth of head 16 inches, Thickness of neck is 8-9 inches (Dale says poss 1 foot);Oudemans total is 55 feet, Dale's total is 40 feet: this is close to the average of most sightings by both Dale and Dinsdale (And Heuvelmans if the estimation of 60 feet in most Longneck cases is equivalent to Oudemans' 55)
C) Length of head, 3 feet: length of Neck 17 1/2 feet: Breadth of head is 2 feet: Thickness of neck is 16 to 18 inches; Oudemans length is estimated as 83 feet, Dale's est is 60 feet, and this corresponds to the Daedalus' SS in 1845 according to Oudemans, one of the standards he uses to derive all the measures from. This might equivilate Heuvelmans' Merhorse, probably not so large really and Dale thinks not nearly so common as is often assumed. All of Oudemans larger estimates may be safely ignored and the largest estimates are probably mistaken sightings of whales according to Dale.

The proportions of the neck were also as specified by Sir Henry Rostron in an earlier blog entry and I took pains to draw attention to it then. Below are more views of the head and neck from Loch Ness Witnesses. (Torquil MacLeod to the left, Miss Margaret Munro top right, and the original nighttime sketch by Arthur Grant at right bottom. This last corrects the figure by Putting the tail back on the tail end after it had been drawn as separately in order to get it all on the same sheet of paper:

Below are some typical Sea Serpent head and  postures taken from many reports and in the first examples utilizing Bruce Champagne's sea-serpent models as being neutal to the debate; First is te fully erect periscope with a "Caddy" report inset as a crioss-reference. This is typically only assumed when the animal is fully stalled or is only moving forward very slowly: one or two reports of sea serpents at full erection swimming forward at good speed are suspicious for that reason alone and at least one of these may be describing a waterspout.

 

 

Next is the creature with the neck thrown forward and up at an angle, which can be assumed at a good rate of speed. N such occasions the creature seems to be alarmed at disturbances at the surface. A model for the New England Sea Serpent in the 1800s is the inset here, This posture will commonly throw up a standing wave in the wake, hence the "String of Buoys" effect in the inset illustration.

 

 

 

Above, two good Sea Serpent reports with the head and neck on the incline to various degrees. The Valhalla sketch has been flipped horizontally and the original is shown at the end of this article.

And finally there is the actually typical swimming posture with the head and neck down in the water and pointed straight ahead. on such occasions only the head at the end of the neck may break surface

 

 The following drawing taken from Tim Dinsdale's Loch Ness Monster but "Recognised" in Florida

has the neck bending about halfway along. It is because of this that a good many reports and most of the earlier authors underestimate the true length of the neck. I have indicated where I make the division of the length from snout to vent to be broken into halves of nearly equal length

 

 

The Morgawr photos off Cornwall may or may not be legitimate but they DO illustrate what is usually described as fishing posture with the neck in an arched shape. From the arched shape the neck can also move from side to side or forward to probe around, or it can plunge downwards.

 

 

And so below here are my mock-ups showing a Longneck as a Plesiosaur at scale to a human figure, illustrating these basic moves to the head and neck as are typically mentioned in the reports:

 

 

First the typical swimming posture with the neck pointed straight ahead and down in the water,

 

Secondly with an upward curve from usually the forward half of the neck,

and this can be a shallow S-curve

 

Next is the position moving ahead at speed on the surface with the neck inclined forward at an angle, evidently assumed when there is a perceived threat at or above the surface of the water

 

Next the arched neck posture assumed to be used in fishing

(Inset, the open mouth and tongue in proportion as also reported)

And the full periscope, which is rarest of all and usually assumed with little or no forward motion.

This is actually an s-shaped curve with the top 1/3 bending as much as the bottom 2/3, which is in good agreement to other indicators of the neck flexibility.

 

 

There are also occasions where the front part of the neck is making a curve at the top like the upper part of a C curve, and this old sighting of the New England Sea Serpent illustrates that curve:

 

 

This illustration of the Scandinavian sea serpent also shows the same position, also the size of the mouth (gape) when opened. The illustration intends to show the mane but the nature of the mane is described differently in different reports. Often it is said to be a fin or of a fleshy nature. 

 

Loch Ness Monster as reported in 2010

 

Now the point of all of this is that while the necks of Plesiosaurs are made up of many vertebrae with many cartilaginous joints between them, the necks of mammals ordinarily come with the seven neck bones (And the first one at the base of the skull does not count for much in any lengthening of the neck) Below we have a direct comparison between the skeletons of a giraffe's neck (Photo inset) and a Plesiosaur's neck (Public-domain drawing) Please note how long the individual vertebrae are in the giraffe's neck.

 

However the Longneck's neck is clearly NOT the same as the giraffe's neck: it is at the same size for the head, and the same thickness but at least double the length of the neck proportionately.

 

At this point the vertebrae are stretched to the length of more typical limb bones, being something like two or three feet long. The joints between them are more like elbow joints between the elongated bones. Please bear in mind that the vertebrae cannot bend in the middle, they can only bend at the ends. To compare again, here is the Zakariya al-Qazwini Bestiary Longneck from just after 1200 (One of the same series we have been looking at recently) This still has recognizably a littler curve at the top and a longer curve at the bottom, to make an overall stretched-S shaped curve

 (This one also shows the mane as spikes)

 

 

Already when you have a giraffe bend its neck, it does so stiffly and forming angles rather than smooth curves. In the photo below, the giraffe's neck folds over as a straight segment at the top because there is only one bone in there. It cannot make a nice continuous curve because it needs more vertebrae to do that. It cannot make anything comparable to a sea-serpent's S-curve or C-curves for that reason. There are not enough joints in the neck to make the curves go that way. Instead of a curve you get a set of angles.

 

 

Please refer to the reconstructions for Heuvelmans' and Oudemans' hypothetical long-necked pinnepeds at the top of this page: I have indicated where the vertebrae are going to have to be if those are going to be mammalian necks. The front half of the neck is going to have three vertebrae only at most, and those three vertebrae are not going to make a smooth curve. What you will have will be a series of angular kinks as I tried to convey to Darren Naish in my eatrlier drawing. For the kinds of curves we have frequently illustrated (and shown in samples above), my guess is that we would need two or three times the number of joints in the place of the hypothetical giraffe-like long pieces, in order to make the curves to have the sufficient bending for a smooth curve instead of a stiff bend at an angle. And once again, you are going to have to have vertebrae at least two feet long each in order to get the neck as long as you need it to fit these reports (Not a few reports but the majority of reports, worldwide and over the span of centuries) You are not going to get a nice tight circular curve over a five-foot length of neck such as the top of the Periscope or C-curve, what you will have will be two long pieces bent at right angles to each other for that same given length of neck..

 

Bending the longneck's neck: at 4 feet of neck the mammalian longneck has two vertebrae
to execute a tight curve but can only manage to fold at right angles (Left) at a 4 foot length of neck
with six vertebrae instead (Right), it is much easier to make regular curves in the neck. 

 

Below is Dale's plan drawing for a typical longneck using the statistical averages common in many reports and basically it is once again like the Oudemans, Sanderson and Dinsdale reconstructions, borrowing a little from each one but making more specifications including the larger flippes on this model. I have a later, improved version of the drawing that has made the numbers on it more readable

 

 

 

Below is a selection of Sea Serpent and Loch Ness Monster stills selected from many candidates by Scott Mardis, Jay Cooney, Dave Francazio, myself and some of our co-workers as being possible candidates for the Longneck category. The purpose here is not to dissect and criticize them but just to give a general overview of what the evidence looks like.

 

Two of the more controversial photos, from Loch Ness and from the "Patagonian Plesiosaur" Nahuelito

 

 

And the Valhalla illustration in its original orientation. It seems there are

different drawings of it pointed in either direction. 

 

ADDITIONAL:
My opinion was and is that some of the reports ascribed to the Mokele-MBembe are probably the same type of water monster as elsewhere and that in some cases, the reported dimensions match the Loch Ness Monster. That does mean specifically the reported dimensions of the neck. On this earlier blog posting:
 http://frontiersofzoology.blogspot.com/2012/11/reposting-congo-dragons-and-colossal.html

I included this depiction of a Mokele-MBembe which struck me as being more reminiscent of a Plesiosaur rather than a Sauropod dinosaur, and it definitely shows many vertebrae in the neck:

Furthermore there are many native depictions of water monsters and dragons the whole world over and not one of them shows only a few vertebrae in the neck, they always show many vertebrae in the neck. In this one the limbs are depicted oddly, but I think the idea is still that they are flippers rather than feet. In other depictions, the flippers are much more obviously so.

And here is the large file that the CFZ left off in the 2009 printing of the article

Native LongNecker Depictions Worldwide

Surviving Plesiosaurs as Vs. Longnecked Seals as Longnecked Sea-Serpent candidates

Surviving Plesiosaurs as Vs. Longnecked Seals as Longnecked Sea-Serpent candidates

In assessing the likelihood of any candidates for the Plesiosaur shaped sea-Serpent categopry, some basic anatomical considerations have got to be considered before any one of them becomes an acceptable alternative to the basic and obvious suggstion that the best candidate for sightings of Plesiosaur-shaped creatures would automaticaly BE Plesiosaurs. In making the suggestion that such sightings might be adequately accounted for by hypothesizing a type of abnormally long-necked seal, the rather glaring problem comes up that pinnepeds are fairly advanced, fairly intelligent creatures with good-sized brains in relation to their body size. This is understandable because most mammals have been developing along a trend towards larger body size and greater intelligence throughout the Cenozoic. Plesiosaurs, on the other hand, have tiny heads and tiny brains, of "Dinosaurian" proportions. The proportionate sizes of the brains are indicated as red dots in the illustrations to the left. The immediate problem is that the actual sightings do specify proportions of a Plesiosaur and not a Pinneped (see reconstruction of Bernard Heuvelmans' "Longnecked" creature at the top) There does not seem any rational reason why a large-brained Pinneped should atrophy down to having a Plesiosaur-sized brain outside of the fact that some theorist or another wants to force the sightings into such an artificial mould. This is a very real problem: many sightings specify that a creature under observation may have a head as large as a the head of a dog or a horse
at the end of a neck perhaps ten to fifteen feet long and far end, and leading into a body the size of an overturned rowboat, much larger of a body size than would ordinarily go with a mammal with a head of such a size. And the standard reconstructions made up from the sightings do allow for what the sightings describe. Heuvelman's Longneck modifies the general consensus of reports only in that it leaves the tail off (the tail is commonly reported in about 10% of the cases. In Heuvelmans' reconstruction, he easily discounts the 10% in favour of a very few reports which seem to specify that the creature under observation had no tail.These reports ordinarily do not really specify so long a neck or so small a head)

The reconstruction below in shading is Dinsdale's reconstruction for The Loch Ness Monster, leaving the variable humps off of the back (Heuvelmans, Sanderson and Dinsdale each specify that the size and the shape of the humps can vary and that they are not permanently fixed in shape or position: this is either because they are filled with fat or oil, or they are airsacs. For the sake of brevity we can allow that they are made of oily fat and their shape can be altered by water pressure as Heuvelmans states) Dinsdale's reconstruction is a good one and not so much shaped by preconceived notions; and other reconstructions such as those made up by Sanderson and Mackal tend to these proportions. Oudemans' model differed only in that he thought the tail was longer, an opinion not borne out in later observations. My own independant reconstruction for animals in this category are below Dinsdale's. (These are compiled from statistical analyses of both worldwide sightings in the category as a whole anompaubcategories defined by geographic region  and each one analysed separately; the two sets of data both tend to fall within good agreement with each other)

For a comparison of proportions, Oudemans' page 505 of The Great Sea-Serpent gives the proportions of- a length of head at 3/4 of a foot goes with a neck 4 feet long and a trunk just over 4 1/2 feet long (Thus about the size of a large sealion or a small walrus); a head a foot long goes with a neck six feet long and a trunk about 7 1/2 feet long, this being the size of Grant's creature seen on land at Loch Ness; a head 2 feet long goes with a neck 12 feet long and a foot thick behind the head, and a trunk 15 feet long, which can be looked upon as just about the "Standard model" when seen under good conditions in freshwater or near to shore, worldwide, and is probably the average size for an adult female or subadult male; and a creature with a head about a yard long has a neck about 18 feet long and a trunk  just over 22 feet long, would be a big male and the size of the Daedalus SS, commonly stated as "60 feet long" although in reality it is probably several feet less. Oudemans was taking figures from sightings at sea, which always tend to be somewhat larger and less precise than their inland counterparts, going by what the statistics indicate. The larger sightings are more strikingly coloured and with more distinctive markings, and are reasonably construed as males.

The mane is reported on some larger individuals but in the majority of "maned" reports, the animal is not verifiably of the type we are discussing. In some cases, such as the Corinthian SS illustrated by Heuvelmans, it is unmistakeably the same sort of creature. Oudemans states that it is most often noticed as an irregular (jagged) outline on the larger individuals, and it is most often the same colour as the rest of the animal. The maned males also have the more distinctive colouration: brown, reddish brown and in a minority of cases, greenish brown. The texture of this "Mane or fin" is classically compared to the leaves of kelp, and ordinarily it is a "Mane" of the upstanding type rather than the flowing type. All reports of scales or spikes as well as hair or bristles refer ONLY to the mane: some witnesses have inapprpriately assumed the whole body must be covered with the same material, be it hair or scales. The body is generally smooth and bare in most other parts, and it is sometimes roughter but only along the spine where the mane is.Oudemans also notes that it runs the whole length of the neck and midline of the back: it seems this also continues down the top of the tail in some observations. In Northern latitudes, maned individuals are seen most often in the spring continuing on into early summer and least often in the autumn; a few reports seen in winter seem to indicate maneless individuals out of the larger reports which otherwise agree with the maned type!.

Kelp. Rather than actually being hair or even vascularized fibers such as Heuvelmans and Sanderson hypothesize, the material of the mane is most often compared to leaves of kelp. That describes  long flat strips of skin rather than actual hair or scales that seems to grow to different lengths at different times of  the year and is evidently shed or absorbed otherwise.

Roy Mackal compared this continuous crenelated fleshy mid-dorsal fin which enhances the male's vertical profile and makes it seem larger  to the breeding array of some newts; and upon some consideration, it might actually be analogous to the newt's backfin in breeding array in that it seasonally grows longer/higher and more jaggedly obvious: it is also probably important that it also goes with the individuals with the richest colouration. Since this organ seems to be somewhat keratinized (and the fleshy members of it are sometimes compared to rolls of cotton batting, coconut fibers and even wood shavings), seasonal, but also that it often seems patchy and missing along parts of the length in some individuals but-this is important-missing from different sections of the neck or back in different individuals and on different occasions, I believe the material serves as a harmless means for males to engage in ritual mating contests without doing each other serious injury. Essentially, agression would be displaced into hair-pulling contests.  Tending to confirm this observation is the fact that reports of "Whiskers" such as in the Corinthian case are obviously showing  the same mane material but lying crosswise in the creature's mouth, exactly as if a male had just pulled a mouthful of material off of another male's mane but not at all in the position the "whiskers" naturally would be if they WERE whiskers, and some reports feature a male "Merhorse" behaving agressively toward humans in a small boat and spitting such pieces of a rival's mane out of its mouth while doing so!

Here are some speculative reconstructions I did of what a long-necked seal would actually look like: in this case the ONLY change being made is that the vertebrae in the neck are being lengthened and neither the head nor the body changed in their relative sizes. The end product in no way resembles any of the reports and has far too mant mechanical difficulties to get around. Incidentally while Plesiosaurs had no problem with doing such a thing as multiplying the number of vetebrae, placental mammals as a rule cannot manage that part either. A seal, a giraffe, a shrew and an elephant each have only the basic seven cervical vertebrae. Making a seal as long-necked as a giraffe does literally mean putting a giraffe's neck on the seal. This would not seem
to give the poor seal any practical advantage whatsoever, and it makes both swimming in the water and walking n the land both more difficult.

Reconstruction of a Sea-serpent theory by Rev JG Wood made by Oudemans in his book The Great Sea Serpent. Oudemans DIDN'T go for this idea at all and thought it was laughably unbalanced and awkward. He opted for his long-tailed long-necked seal version instead.

http://www.thelordgeekington.com/2008/09/flexibility-of-plesiosaur-necks.html

From Lord Geekington's discussion on the flexibility of Plesiosaurian necks:

Maybe having an unusually flexible neck in the vertical plane is useful for living in shallow near shore marine, brackish and freshwater environments - the juvenile in question was from marine deposits. Also problematic is that freshwater plesiosaurs in Australia were apparently subjected to cold to near-freezing conditions according to Kear (2006) - I couldn't imagine a 28 inch juvenile managing that.[like many living animals, they probably had young in spring and summer to give the young a window of advanyage during the warmer months-DD] Freshwater plesiosaurs are potentially very interesting, they've been found worldwide from the early mid-Jurassic to the Late Cretaceous by the way, and I'd be curious about any morphological adaptations.
...
Back to plesiosaur necks, how flexible are they anyways? The genesis of this post was a paper by Zammit et al. (2008) which rigorously examined just that in the elasmosaur Aphrosaurus. The authors created life-sized 2D models of the vertebrae in dorsal and lateral view and used the minimum and maximum amount of intervertebral cartilage to create a possible range (Zammit et al. 2008). Models were also made of a boid, snake-necked turtle and sea lion for comparison - these tended to produce slight underestimates (Zammit et al. 2008). It turns out that Aphrosaurus could bend its neck 87–155° in the dorsal plane - far from the 360°+ needed for a swan-like posture - and motion in the ventral plane (75–177°) and lateral plane (94–176°) appears to have been greater (Zammit et al. 2008). The authors mention an unpublished master's thesis which showed a similar pattern from Cryptoclidus and Muraenosaurus (both cryptoclidids) and noted that the vertebral centra in those genera had concave articular faces and rounded lateral margins, imply more vertebral movement (Zammit et al. 2008). Exact figures were not given, but the vertebral count (~40) was lower so the cryptoclidid necks are not necessarily more flexible overall.

Zammit et al. mention that cervical zygapophyses are inclined more posteriorly so the back of the neck has increased vertical flexibility at the expense of lateral flexibility; the amount of flexibility also decreases going towards the posterior end of the neck. Previous papers (which I can't access) mention a "tongue in groove" structure also in the posterior part of the neck may be analagous to zygantrum–zygosphene articulations in snakes, which reduce torsion (Zammit et al. 2008, Moon 1999). Elasmosaurs seem to lack a mid-neck increase in flexibility that appears to have been present in cryptoclidids (Zammit et al. 2008). As far as function, Zammit et al. conclude that a strait held neck combined with lateral and/or ventral movement to capture prey is plausible but arching and slight s-curves appear possible as well; these are consistent with models of elasmosaurs as benthic grazers, ambush predators, and active predators using snake/turtle-like strikes.

All Right Then: Plesiosaurs that lived in the inshore/freshwater habitat had greater low-temperature tolerance (down to freezing) and probably had greater neck flexibility in the dorsal plane. And plesiosaurs like Muraenosaurus and Cryptoclidus exibilty than Elasmosaurs (some papers would suggest as much as twice as much) while Elasmosaurs had more lateral flexibilty (ditto). And we have already got an indication that the most consistent classification for suspected postCreataceous Plesiosaurs to Cryptoclidus. And the "slight S-shaped curves" are exactly what comes out as the "Periscope" position when you just see the front part of it. Furthermore, my own studies indicate the neck flexibility of Longnecked Sea Serpents and their Freshwater equivalents is that their necks have exactly that midneck change in flexibility with more flexibility toward the front.

You heard it first from The Lord Geekington, Folks!

Fossil showing flexibility inherant in the Plesiosaur's neck

Illustration of a Plesiosaurus skeleton. This position IS what a "stretched-S" is supposed to be, in other words, allowable for Plesiosaurs (see text). At the site where this illustration was taken, the statement was made that the position of the neck should not be like this because the neck should be held in the reverse manner than it is in most amniotes, basically because the experts wanted it to be that way. http://svpow.com/category/other-long-necks/page/2/

The site Plesiosauria.com (the Plesiosaur Directory) merely says "There have been many differing interpretations of plesiosaur neck posture and function. Indeed, the [posture and] function of the long plesiosaur neck is still controversial and unresolved today (Martill et al. 1994)"

Which is much the same as  the matter of how Plesiosaurs even swam in the first place)

http://www.plesiosauria.com/neck_function.php

As Tyler Stone points out, not all surviving Plesiosaurs need be Longnecks
And there are a number of reports which sound like smaller shorter-necked forms

Below is the "Cryprtopinnepeda Panopoly" from an article by Darren Naish et al: these reconstructions fail to reflect any subcategories of reports in any real sense and they include some anatomical absurdities, such as in the elongation of the neck and the large disparity between brain and body sizes. I believe that each of these models is based on a false reconstruction going on some highly speculative readings of certain reports. In specific, the smallest one seems to be an illustration of Steller's Sea Ape as interpreted by Roy Mackal, with no forelimbs, and the largest one could be a redrawing of the invalid reconstruction for "Cadborosaurus willsi." In any event, the models are anatomically impractical and contradict expectations for pinnepeds due to the reasons outlined above.