A review of the evidence for living plesiosaurs

One of the topics I’m most frequently asked about as a plesiosaur palaeontologist is my opinion on the Loch Ness Monster and other monsters purported to be present day plesiosaurs. In this review I’ll cast a critical eye over the evidence for living plesiosaurs.

Before I delve into the details I should state that I have no agenda. I have no reason to deny or circumvent any evidence for living plesiosaurs. On the contrary, it would be wonderful if plesiosaurs existed today, as a plesiosaur researcher this would provide an exciting opportunity to study a real specimen and answer some of the big unanswered questions about plesiosaur biology. The aim of my research is, after all, to understand plesiosaurs. This article will provide an objective and critical review of the evidence for living plesiosaurs.

The fossil record
The youngest known plesiosaur fossils come from Late Cretaceous rocks. This leaves a 65 million year gap in the fossil record from the end of the Cretaceous Period to the present day. On this basis plesiosaurs are regarded to have gone extinct 65 million years ago. The discovery of a fossil plesiosaur in younger Cenozoic rocks would possibly strengthen the case for living plesiosaurs, but none are known. The story of the coelacanth fish is often presented as a tale of caution for sceptics to take heed. However, the case of the coelacanth is not analogous because living plesiosaurs, as air-breathing reptiles, must surface frequently to inhale. This means they would be unable to stay submerged in the deep oceans as can fish such as the coelacanth. While this does not completely rule out the possibility of plesiosaurs surviving to the present day, this significant gap in the fossil record is, at the very least, inconvenient for proponents of the living plesiosaur hypothesis.

Photographic evidence
Even a good photograph of a clearly plesiosaur-like organism would not provide conclusive proof for the existence of living plesiosaurs. It is too easy to hoax photographs, increasingly so with the advent of Photoshop etc. A compelling photograph, or preferably a good series of photographs taken in quick succession, would certainly warrant further investigation. To this day, the most compelling photographs of possible living plesiosaurs have either been admitted or demonstrated to be hoaxes (Fig. 1); confidently identified as other known living organisms or inanimate objects; or are of such ambiguity, low resolution, or bad quality, that they remain insufficient as evidence for anything. All of the underwater photographs purported to show the Loch Ness monster have either been identified as tree trunks or demonstrated to have been retouched and manipulated (

Fig 1. One of the hoax Nessie photographs

Video evidence Video evidence is a step up from photographic evidence, but is thin on the ground. Proponents of living plesiosaurs provide the ‘Dinsdale film’, taken in 1960, as the most compelling video evidence for a monster in Loch Ness. For example, Bauer (2002a)(p.227) states that this footage represents the “strongest objective evidence for Nessies”. The film contains a “large hump [which] moves in a curving path, submerging after a time” (Bauer 2002b) (p. 457). A moving hump is not robust evidence for a living plesiosaur.

There are plenty of reported sightings of sea monsters (see the works of Huevelmans for thorough accounts), but anecdote is the least reliable form of evidence. There are two main problems with sightings. Firstly they are untestable. Even if the witness is honest, this brings us to the second problem with sightings: eye witness accounts are notoriously inaccurate. This was demonstrated in the BBC documentary, ‘Search for the Loch Ness monster’. A simple experiment was performed in which a stick was raised out of the water the Loch for a few seconds in view of a group of unsuspecting tourists. The group were asked to draw what they saw and a surprisingly large number depicted a ‘head’ on the end of a ‘neck’. It seems that we sometimes see what we expect or would like to see. The human brain is fallible, open to misinterpretation, and even the most sceptical observer can be misled.

The best known sonar evidence is of too low resolution to be conclusive. It may simply represent physical artefacts in the water, such as different temperature layers (Bauer 1988).

Fig 2. The rotting corpse of a lamniform shark captured by Japanese fishermen in 1977.

Purported living plesiosaur photographs and sightings often portray or describe animals that do not match the basic body shape present in all known plesiosaurs. For instance, plesiosaurs do not have two humps or diamond shaped paddles, as suggested by Scott and Rines (1975) in their paper ‘naming the Loch Ness monster’. Recent studies of plesiosaur neck flexibility and posture have shown that long-necked plesiosaurs could not keep their necks out of the water as described in some sightings. Furthermore, the necks of plesiosaurs were held horizontally in a relatively straight and rigid pose and were not extremely flexible as erroneously portrayed in early palaeontological literature and paleoart. If the concept of living plesiosaurs is a purely cultural phenomenon then we may predict eyewitness accounts to ‘adapt’ to new scientific consensus. Proponents of living plesiosaurs sometimes suggest that evolution may explain the discrepancy. While possible, this seems to be a combination of clutching at straws and special pleading.

In an attempt to explain the relative lack of sightings in Loch Ness, Bauer (1988)(p.14) suggests that “Nessies don’t spend much time at the surface” and that “no one, including those who believe in them, should expect to see one”. However, plesiosaurs had lungs, like whales, dolphins and sea turtles. As air-breathers they must surface several times a day to breathe. This simple fact weakens the case for a viable population of living plesiosaurs in any lake in close proximity to human settlements. In the ‘Dinsdale film’ the “last sequence shows a definite paddling action” (Bauer 2002)(p.229). However, we know plesiosaurs did not paddle, they flew underwater, like penguins do. They used predominantly up and down strokes rather than back and forth strokes (e.g. Robinson 1975 and others).

Fig 3. The head of the corpse (indicated by black arrow). a lamniform shark captured by Japanese fishermen in 1977. Compare with the shark skulls.

A real specimen of a living plesiosaur, or a recently deceased one, would provide sufficient scientific evidence. Although no living specimens have been reported discovered, many corpses have been claimed to be plesiosaurs. The most famous example is the carcass of a large rotting animal caught by Japanese fishermen in 1977, declared to be the remains of a plesiosaur. There are numerous lines of evidence that discredit this claim and confirm that it was a rotting basking shark (Kuban 1996). Nevertheless, it is quite easy to see why an untrained eye might interpret this as a plesiosaur (Fig. 2).

Perhaps the most convincing feature is an apparently small skull on a long neck (Fig. 3). However, when compared to the chondrocranium (braincase) of a basking shark (Fig. 4) it is clear that the similarity with a plesiosaur is minimal and superficial. The large jaws of the filter-feeding shark have become detached to give the impression of a small head (the chondrocranium), while the flesh between the head and the fins has rotted away to give the appearance of a longish neck.

Fig 4. Lamniform shark skulls (image from Maisey 1985, ‘Relationships of the megamouth shark, Megachasma’, in the Journal ‘Copeia’). The jaws (white) are held loosely by soft tissue to the chondrocranium (grey). When the jaws fall off during decomposition, the remaining skull (grey), one might argue, looks superficially and vaguely like a plesiosaur skull.

Furthermore, biochemical analysis of samples taken from the specimen have also confirmed it was a shark. The same reasoning applies to all of the other carcasses washed up on shorelines around the world. Corpses are washed up all the time, in various states of decay. Only the most decomposed and distorted ones are considered to be plesiosaurs. It is also interesting to note that no plesiosaur carcasses have ever been washed up on the banks of Loch Ness. A block of five plesiosaur vertebrae were reported from the banks of Loch Ness in 2003, but although nobody has publicly taken responsibility, the specimen was clearly planted as a hoax or publicity stunt, or left there by accident, since the vertebrae were fossilised remains (not recent bones) preserved in a Jurassic rock type found many miles away from Loch Ness.

Historic illustrations
An illustration claimed to be recent aboriginal art depicts a plesiosaur, but it cannot be demonstrated as authentic (Fig 5). The typical medium of aboriginal art is rock but the plesiosaur artwork is not. The artwork also bears striking similarity with existing modern artwork and shares the same anatomical errors. Even if the artwork was genuine, which I don’t think it is, plesiosaur fossil remains are known from Australia, so it would be possible that the illustration is based on fossil evidence.

Fig. 5. Purported aboriginal art – not authenticated.

There is no scientific evidence supporting the existence of plesiosaurs living today. There is a lack of compelling photographic or video evidence, demonstrable plesiosaur corpses or living specimens. Unfortunately, living plesiosaurs almost certainly do not exist today.

Epilogue – so why do people still believe in living plesiosaurs?
This is an important question because while we have reviewed the evidence here, not all belief is based on evidence. There are three possible reasons for this. The first and most widespread reason is that many people may want to believe in living plesiosaurs because it is exciting (it really is!) and they the the evidence uncritically, at face value.

The second reason applies to those who have dedicated much of their time investigating ‘living plesiosaurs’ and may have developed faith in the idea. In a personal article by Bauer, he describes his involvement searching for Nessie and reveals a touching emotional tie with his subject matter. He claimed that photographic proof was “no longer important to me…No such proof could add to the gifts that had already come to me through the mediation of Nessie”. While proof may not be important to Bauer, it is important to me.

The third and potentially dangerous agenda is creationism and anti-evolution propaganda. Given that all of the evidence indicates plesiosaurs are extinct and that the youngest plesiosaur specimens in the fossil record date to 65 million years ago, it is easy to understand how a creationist might perceive the existence of living plesiosaurs as evidence against evolution and for a young Earth. In reality, the discovery of living plesiosaurs would not threaten evolutionary biology. Organisms may evolve at extremely slow rates, as has been documented in numerous organisms. Creationists may also believe that the discovery of living plesiosaurs would cause geologists to rethink the age of the Earth, but the distribution of fossils throughout the rock record has no impact on the absolute dates of the rocks. Unfortunately, not everyone understands, wants to understand, or accepts, the robust science in support of evolution and the age of the eEarth. For these people, the propaganda for living plesiosaurs must seem quite convincing, and I hope they find this article for at least a little perspective.

I would like to thank Phillip O’Donnell for reminding me to write this article and Henry Bauer for making much of his published work freely available online. Thanks also to Nizar Ibrahim for comments, and everyone at who commented on this article. Cheers guys!

Bauer, H. H. 1988. Loch Ness Odyssey, Snowy Egret, 51, 8–15
Bauer, H. H. 2002a. The case for the loch ness ‘monster’: the scientific evidence. Journal of Scientific Exploration, 16, 225-246.
Bauer, H. H. 2002b. Common knowledge about the Loch Ness Monster. Journal of Scientific Exploration, 16, 455-477.
Robinson, J, A. 1975. The locomotion of plesiosaurs. N. Jb. Geol. Palaeont. Abh. 149, 286-332.
Scott P. and Rines R. 1975. Naming the Loch Ness monster. Nature 258, 466-468.
Kuban, G. J. 1997. Sea-monster or shark? An analysis of a supposed plesiosaur carcass Netted in 1977. Reports of the National Center for Science Education 17, 16-28.