Surviving Plesiosaurs as Vs. Longnecked Seals as Longnecked Sea-Serpent candidates (PART ONE)
(Sydney’s note: This is an article posted by Dale Drinnon over at Frontiers of Zoology earlier this year that I have been meaning to share with you guys, please let me know what you think of his thoughtful assessment.)
In assessing the likelihood of any candidates for the Plesiosaur shaped sea-Serpent category, some basic anatomical considerations have got to be considered before any one of them becomes an acceptable alternative to the basic and obvious suggestion 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.
Pinnipeds or fin-footed mammals are a widely distributed and diverse group of semiaquatic marine mammals comprising the families Odobenidae (the walrus), Otariidae (eared seals, including sea lions and fur seals), and Phocidae (earless seals).
The proportionate sizes of the brains are indicated as red dots in the illustrations above and below.
[End of Addendum]
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 mold. 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.
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 independent 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 many 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 on 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.
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 inherent 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.
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)
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.