Tetrapod Zoology


This weekend (17th-18th April 2010), the 9th European Symposium of Cryptozoology is being held at Engreux in the south of Belgium. I meant to attend and give a talk, but had to cancel for financial reasons. And it’s just as well that I did, given that virtually all flights from out of the UK have been cancelled due to the Icelandic eruption (the consequences of this eruption are interesting: the sky here in England is free of planes and contrails, and a very fine covering of ash covers cars and other objects). Anyway, my non-attendance in person meant that I was invited to submit a poster instead, and here’s a screen-capture for your enjoyment (yeah, ridiculously small: sorry about that).

The poster covers the same sort of stuff I’ve been saying for the past 12 years or so, and won’t be new to anyone who’s read my cryptozoological articles, or attended my talks. The text from the poster is reproduced below. There are a few things that need to be said in addition, however [below: the three horsemen].


The data I compiled for plesiosaur, mosasaur and coelacanth diversity is now substantially out of date and would need to be redone from scratch if I wanted to publish it now (the diagram used on the poster was produced in 1997: that’s a LOOONG time ago in terms of palaeontological publications). After the poster’s text was completed (the text is based on the talk I gave at the Centre for Inquiry sea monster meeting of November 2009), Benson et al. (2009) published their study of Mesozoic marine reptile diversity across time. This study compared recorded diversity (as in, the actual number of fossil species we know about) with the biases of the geological record (the number of fossil-bearing rock formations is not equally spaced through time). They found that marine reptile diversity declined in the last two stages of the Late Cretaceous (a discovery consistent with data from some other groups of Cretaceous organisms: they seem to have been declining and ‘stressed’ prior to the end-Maastrichtian event). This result differs from what I’ve shown in one of my diagrams because, like I said, my data was compiled pre-1997 and is now very much off. However, none of this changes the take-home message: that the record of coelacanth diversity is very different from that of Mesozoic marine reptiles.




Throughout history, people have reported sightings of large marine animals that do not seem to match any species recognised by science. The recent discovery of new, large marine animals (e.g., megamouth sharks, Indonesian coelacanths, Bathyraja hesperafricana, several new cetaceans), combined with data from discovery rates plotted over time (Paxton 1998, Raynal 2001, Solow & Smith 2005, Woodley et al. 2008), shows that the future discovery of large marine animals is not at all far fetched or unlikely. Furthermore, statistical analyses of eyewitness data indicate that most sightings occur at close range, rendering misidentification of known species unlikely (Paxton 2009). Accordingly, at least some ‘sea monster’ accounts may well describe real, undiscovered species.


An idea that’s persisted throughout more than 100 years of cryptozoological literature is that ‘sea monsters’ might be ‘prehistoric survivors’: that is, they might be the modern-day descendants of creatures otherwise known only from the fossil record (specifically, plesiosaurs, mosasaurs and basilosaurid whales). This hypothesis has become known as the prehistoric survivor paradigm, or PSP. While the PSP has been endorsed throughout the writings of Heuvelmans, Mackal and Shuker, it is not supported by all cryptozoologists.


For groups such as plesiosaurs, the fossil record shows that they died out at the end of the Cretaceous, and there are no post-Cretaceous fossils. Furthermore, long-necked
sea monsters are described as being only superficially similar to plesiosaurs, and lack the unusual features of these animals. PSP advocates have suggested that post-Cretaceous plesiosaurs might have evolved a list of new anatomical and behavioural features (such as fur, whiskers, inflatable humps etc.) that make them look like modern sea monsters, and less like fossil plesiosaurs (Shuker 1995). While this possibility cannot be discounted, it is nothing more than unfounded speculation, and – perhaps most importantly – it is simply not the most likely explanation of the data: in this case, that unusual pinnipeds might account for the sightings.



The most extreme version of the ‘evolved plesiosaur’ argument was put forward by Bousfield & LeBlond (1995). After proposing that the Naden Harbour carcass (Fig. 3) represented a new extant vertebrate species (dubbed Cadborosaurus willsi), they interpreted it as a reptile, and specifically as a plesiosaur. Plesiosaurs had broad, rounded bodies, enormous flattened pectoral and pelvic girdles, an interlocked, stiff basket of gastralia (= ‘belly ribs’), two pairs of wing-like flippers, and a short tail. C. willsi (assuming that it is a real animal!) is slender and serpentine, does not rely on its limbs for propulsion, has a paired, fluke-like tail structure, is furry, and sometimes has horns and/or whiskers. The hypothesis that C. willsi might be a plesiosaur can be rejected (Bauer & Russell 1996, Naish 2001, Woodley et al. 2008).

Bousfield & LeBlond (1995) used data from an alleged juvenile specimen to endorse their interpretation of C. willsi as a reptile, but the account in question (Captain William Hagelund’s account of 1968) most likely describes a pipefish (Woodley et al., submitted: Fig. 4).



The fossil record shows that we can be confident about the extinction of plesiosaurs, basilosaurids and other such groups. However, the fossil record is often incomplete and there are sometimes gaps where members of a lineage are absent for some period of geological time. So-called Lazarus taxa belong to groups that seem to have gone extinct, but then re-appear unexpectedly at a later date, or in the modern day. Coelacanths are one of the best known Lazarus taxa. Supposedly, they disappear from the fossil record for more than 60 million years. As a consequence, it is typical to see advocates of the PSP claim that coelacanths provide support for the possible survival to the present of plesiosaurs, basilosaurids and so on. This view can be rejected for three reasons.

(1) The coelacanth fossil record is very different from that of plesiosaurs and other putative ‘prehistoric survivors’: coelacanths dwindled in diversity during the Cretaceous, and in fact for a while were thought to have become extinct long before the end of the Cretaceous. (2) Coelacanth bones are small, fragile, frequently non-diagnostic, and have low preservation potential. In contrast, the bones of plesiosaurs, basilosaurids and so on are dense, erosion-resistant and diagnostic. (3) The supposed 65-million-year gap in the coelacanth record does not exist in any case: in addition to the two living species, a Paleocene coelacanth is known from Sweden, and a Miocene coelacanth was reported in 1997 (Fig. 6).

In fact, so far as we know, there aren’t any marine vertebrate groups that persisted for tens of millions of years without leaving a fossil record: the fossil record for big marine vertebrates is comparatively good (e.g., Bardet 1992, 1994, Benton & Storrs 1994).


  • The idea that big marine vertebrate animals await discovery in the present day is not far-fetched or unlikely, and we should expect continuing discoveries (though whether such discoveries will be anything to do with the ‘sea monsters’ of tradition remains to be seen).
  • The ‘prehistoric survivor paradigm’ relies on special pleading and speculation and can be rejected: plesiosaurs, mosasaurs and basilosaurids are extinct.
  • Coelacanths are red herrings, at least in so far as they can be used as analogues for putative ‘prehistoric survivors’.
  • What data we have on ‘sea monsters’ is not good enough for firm conclusions to be reached about the creatures concerned: we don’t know what they are and need more evidence!

For previous Tet Zoo articles on sea monsters, or marine cryptozoology, or whatever you wanna call it, see…

Refs – -

Bardet, N. 1992. Evolution et extinction des reptiles marins au cours du Mésozoique. Paleovertebrata 24, 177-283.

Bardet, N. 1994. Extinction events among Mesozoic marine reptiles. Historical Biology 7, 313-324.

Bauer, A. M. & Russell, A. P. 1996. A living plesiosaur?: A critical assessment of the description of Cadborosaurus willsi. Cryptozoology 12, 1-18.

Benson, R. B. J., Butler, R. J., Lindgren, J. & Smith, A. S. 2009. Mesozoic marine tetrapod diversity: mass extinctions and temporal heterogeneity in geological megabiases affecting vertebrates. Proceeding of the Royal Society B doi: 10.1098/rspb.2009.1845

Benton, M. J. & Storrs, G. W. 1994. Testing the quality of the fossil record: paleontological knowledge is improving. Geology 22, 111-114.

Bousfield, E. L. & LeBlond, P. H. 1995. An account of Cadborosaurus willsi, new genus, new species, a large aquatic reptile from the Pacific coast of North America. Amphipacifica 1 (supplement 1), 1-25.

Naish, D. 2001. Sea serpents, seals and coelacanths: an attempt at a holistic approach to the identity of large aquatic cryptids. In Simmons, I. & Quin, M. (eds) Fortean Studies Volume 7. John Brown Publishing (London), pp. 75-94.

Paxton, C. G. M. 1998. A cumulative species description curve for large open water marine animals. Journal of the Marine Biologists Association, U.K. 78, 1389-1391.

Paxton, C. G. M. 2009. The plural of “anecdote” can be “data”: statistical analysis of viewing distances in reports of unidentified giant marine animals 1758-2000. Journal of Zoology 279, 381-387.

Raynal, M. 2001. Cryptocetology and mathematics: how many cetaceans remain to be discovered? In Heinselman, C. (ed) Dracontology Special Number 1: Being an Examination of Unknown Aquatic Animals. Craig Heinselman (Francestown, New Hampshire), pp. 75-90.

Shuker, K. P. N. 1995. In Search of Prehistoric Survivors. Blandford (London).

Solow, A. R. & Smith, W. K. 2005. On estimating the number of species from the discovery record. Proceedings of the Royal Society B 272, 285-287.

Woodley, M. A., Naish, D. & Shanahan, H. P. 2008. How many extant pinniped species remain to be described? Historical Biology 20, 225-235.

Woodley, M. A., Naish, D. & McCormick, C. Submitted. A baby sea-serpent no more: reinterpretation of Hagelund’s juvenile cadborosaur removes evidence for the ‘reptilian hypothesis’. Journal of Natural History.


  1. #1 Allen Hazen
    April 17, 2010

    My (layman’s) impression is that the fossil record for large marine vertebrates is if anything LESS spotty than that for large terrestrial vertebrates. (I’d think it would be comparatively easy for a terrestrial species to be limited in its distribution to territory with poor prospects of fossilization, but there have been enough epicontinental seas through enough of geological history that a population of large marine vertebrates is almost bound to leave discoverable remains!)

    Is this subjective impression totally off base?

    (As for SMALL marine vertebrates… I have a longstanding fantasy about conodonts surviving in deep water over subduction zones…. ;-) )

  2. #2 Andreas Johansson
    April 18, 2010

    Coelacanths are clupeiforms? That’s pretty radical! ;)

  3. #3 Tim Morris
    April 18, 2010

    Just one question, why didnt you get Nemo to put a mane on your Caddy/Merhorse?

  4. #4 Darren Naish
    April 18, 2010

    A: because there isn’t one on the Naden Harbour carcass.

  5. #5 Jaime A. Headden
    April 18, 2010

    I would definately say that a lot of a plesiosaur skeleton is fairly non-diagnostic, aside from being able to determine that it is a plesiosaur. In this case, much of the fin structure of a coelocanth should be fairly diagnostic, as would the skull, and associated systems.

    I’m fairly stumped on finding any bony-skeleton animal that is substantively “diagnostic” throughout its sekelton, although I’d be tempted to posit megalancosaurs as being so substantively diagnostic as to make one amazed.

    Mannion and Upchurch have recently published on a metric of associating character states density to skeletal systems to diagnose the completeness of a specimen, and consequently taxa based on said specimen, so I am wondering on its applicability to dense versus sparse skeletal systems in other taxa in creating a stable definition of “diagnostic.”

  6. #6 Darren Naish
    April 18, 2010

    Jaime, I think you misunderstand. The point is this: if you find a plesiosaur bone (usually an isolated vertebra, propodial, or phalanx) you immediately know it’s a plesiosaur bone.

  7. #7 Cameron
    April 18, 2010

    A: because there isn’t one on the Naden Harbour carcass.

    The ‘neck’ of this carcass is quite peculiar – for one thing it isn’t very long, maybe a bit over one ‘head’ length. The side-on photograph makes the ‘neck’ seem particularly thick (somewhat more so than the ‘body’) and lumpy. There is also a projection pointing towards the ‘head’ on the underside of the ‘neck’. LeBlond and Bousfield described the ‘neck’ as “crushed”, although I have a hard time seeing how a long neck could turn into that. Times like this I wish I had a rotting basking shark on hand…

  8. #8 Jim Thomerson
    April 18, 2010

    Comment from a paleontology course lecture. “Usually can’t tell much from a rib. Whether it is from a mouse or an elepant is about it.”

  9. #9 Dave Hughes
    April 18, 2010

    The Naden Harbour “carcass” has always struck me as looking like nothing more than an old boot stuck on the end of a long straggly piece of canvas or some other coarse material. In the absence of any better supporting evidence I think the whole thing should be treated as a hoax.

  10. #10 Bradley Fierstine
    April 18, 2010

    Jim Thomerson: it is just not true that ribs are all but useless. They vary one hell of a lot and can often be identified to specific groups. Isolated plesiosaur ribs can be told from those of other marine vertebrates on the basis of shape in cross-section and histology.

  11. #11 Mark Lees
    April 18, 2010

    If you had travelled youd bestuck now. Im marooned in Tunisia – looks like it will be a few days before I can fly home. (And this keyboard is not qwerty so its doing my head in).

  12. #12 Dartian
    April 19, 2010

    a very fine covering of ash covers cars and other objects

    They thought Iceland would pay her debts in cash, but instead she paid in ash. Just business ash usual, I suppose.

    it is typical to see advocates of the PSP claim that coelacanths provide support for the possible survival to the present of plesiosaurs, basilosaurids and so on. This view can be rejected for three reasons.

    Apart from those reasons you listed, Latimeria also differs behaviourally from the plesiosaurs, basilosaurs and other tetrapods that people usually try to associate with sea serpent sightings. Unlike them, extant coelacanths don’t need to come up to the surface to breathe several times a day (in fact, AFAWK they don’t even voluntarily enter shallow waters), thus further decreasing their likelihood of being encountered by people.

  13. #13 Darren Naish
    April 19, 2010

    Thanks to all for comments/jokes etc. Dave Hughes (comment 9) wrote…

    The Naden Harbour “carcass” has always struck me as looking like nothing more than an old boot stuck on the end of a long straggly piece of canvas or some other coarse material.

    Because people in the region were evidently faking ‘Caddy’ carcasses during the 1930s, hoaxing is a possibility (see Naish (1997): I argued that another, vaguely similar ‘carcass’ – the ‘Camp Fircom caddy’ – was made from kelp stems and other bits and pieces [some diagrams here]). The idea that it might be a partial shark carcass is also on record. I’m inclined to think that it is a vertebrate carcass of some kind: a group of us were talking about doing a critical analysis at some stage.

    Ref – -

    Naish, D. 1997. Another Caddy carcass? The Cryptozoology Review 2 (1), 26-29.

  14. #14 nboujad
    April 19, 2010

    How can we be inform of such meeting or Symposium of Cryptozoology?

    I live in Belgium and I would have like to be there…

  15. #15 Cameron
    April 19, 2010

    Darren (#13):
    a group of us were talking about doing a critical analysis at some stage.

    Unless there are some high-quality scans out there, somebody’s going to have to track down the originals. It would be nice if the actual remains turn up too – but I can’t imagine how much work that would take.

  16. #16 Darren Naish
    April 19, 2010

    Cameron: I’m on good terms with Ed Bousfield. It could happen… pending a trip to BC, of course (and I’m talking about seeing the original photos, in case anyone thought I meant anything else).

  17. #17 Cameron
    April 19, 2010

    Good to know Darren! I was pondering either riding the rails hobo-style or attaching myself to the side of a vehicle like a remora.

  18. #18 Jerzy
    April 19, 2010

    What killed sea monsters? And surviving hominids? And British big cats?

    Cameras in mobile phones. Now, any mariner who claims a sea monster will be immediately asked – so where are the photos?

  19. #19 Erik Knatterud
    April 20, 2010

    I do not believe in sea serpents, I know they exist, because I have seen them three times, at least our Norwegian sea serpents. Besides, they certainly are not mammals. E.K.

  20. #20 MarkGelbart
    April 22, 2010

    I love this website–discovered when researching my now published book: Georgia Before People: Land of the Saber-tooths, Mastodons, Vampire Bats, and Other Strange Creatures.

    The present existence of long-necked pliosaurs can easily be debunked. Hoaxsters represent them with their long necks well out of the water. But vertebrate zoologists have determined that they couldn’t hold their necks above water.

    Hence, another myth bites the dust.

  21. #21 scott mardis
    May 24, 2010

    Dear Darren;With all due respect,I think the head morphology of the Naden Harbour carcass is very hard to reconcile with any mutilated basking shark carcass,despite the great resemblance of the vertebrae in both animals.While I agree with you that C. willsi being a plesiosaur derivative is extremely problematic,I am still inclined to think it may be a legitimate unknown.The body appears too attenuated to be mammalian,yet the head is very mammalian.At the very least,it may represent a very strange eel-like fish. Sincerely,Scott Mardis

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