The Adequacy Of The Fossil Record And Its Cryptozoological Significance
Howdy, the first half-dozen or so of my posts act as mirrors for Reddit posts and adhere largely to that style, just modifying the contents of these posts slightly, I will eventually come back and amend these when I decide on a cohesive format for my posting.
A usual and consistent line of inquiry within cryptozoological
circles is whether a purported cryptid could represent a late-surviving
population of a group of animals thought to be extinct (e.g. "is Mokele-Mbembe a living sauropod?", "if the coelacanth survived,
why couldn’t some other Mesozoic marine animals?"). I’m seeking to
thoroughly challenge most of these lines of thought.
To put it simply, the fossil record is adequate enough to depict the general ecological composition of prehistoric ecosystems, and the absence of certain megafaunal groups is often genuine evidence of absence. Cryptozoology enthusiast’s search for an identity leads them to propose completely anachronistic species as candidates, neglecting that these extinct animals were animals - they had dietary needs, population thresholds to maintain, and were part of complex ecosystems, key parts of which are absent in the modern day. There are no modern examples of “prehistoric survivors” which can justify modern non-avian dinosaurs, arthropleurids, megalodons, or anything of the sort. The only “prehistoric survivors” to be found are insular species which have historically lived in current refugium ecosystems such as islands and mountaintop cloud forests. The prehistoric survivors often proposed range wildly, usually pulling from depictions in popular media, not an actual understanding of these species. The search for an identity for a cryptid is in many cases done despite inadequate information - it’s an outdated practice that ought to die.
This is the argument from Darren Naish’s 2001 paper “Sea serpents, seals and coelacanths: an attempt at a holistic approach to the identity of large aquatic cryptids”, presented here in a shortened form ideally to reach a broader audience.
The Adequacy Of The Fossil Record
The fossil record is incomplete, but not inadequate. This is a significant distinction.
Adequacy is the idea that the fossil record preserves broad-strokes portraits of ecosystems or the information necessary to infer relationships in a satisfactory manner. When a megafaunal group is present, they are almost always preserved, and when they are absent, data from other sites can be analyzed to figure out whether they are likely truly absent. Although the fossil record is incomplete, meaning it does not preserve every animal that ever lived, this fact cannot be used to blindly handwave inferences about the presence or absence of groups. The incomplete nature of the fossil record has often been overemphasized if anything; the fossil record has repeatedly proven adequate enough to demonstrate ancestor-descendant relationships, solidify biostratigraphy, and provide dates of extinction for a majority of megafaunal groups. The adequacy of the fossil record informs paleoecological assumptions which are key to us - the patterns preserved in the fossil record attest to the presence or absence of megafaunal groups.
For further exploration of these concepts, I suggest reading The Adequacy of the Fossil Record, edited by Christopher Paul and Stephen Donovan and cited works within.
I'd like to entertain a brief thought experiment to demonstrate the usefulness of adequacy - let's ask whether or not a living sauropod could have survived the KPG and persist today in the Congo Basin.
Starting off with the facts - it is scientific consensus that sauropods, alongside the rest of the non-avian dinosaurs, died off 66 million years ago. It is also consensus that this extinction was due to an asteroid impact and subsequent long-term climate collapse. Despite the occasional claim to the contrary there are no confirmed appearances of non-avian dinosaurs within the fossil record beyond the KPG boundary (Lucas 2025). Even so, the Cretaceous-Paleocene boundary is a unit of time which is quite under-explored in Africa - fossil discoveries in the region pick up almost 20 million years after the supposed extinction date.
This is where adequacy comes in - we can look at the deposits we do have, and the patterns present in ecosystems elsewhere to judge how likely it is for a sauropod to be present.
After the extinction of the dinosaurs, there is a significant increase in the body size (Bertrand et al., 2022) and biodiversity (Benevento et al., 2023) of mammals. The near-immediate appearance of new, large mammals on
other continents (i.e. Ankalagon, Barylambda), suggests ecological
replacement; the old animals died and the new ones filled in for them. There is some evidence, albeit quite limited, that this is also true of Africa - for example, remains of an arctocyonid mammal in Paleocene Morocco. If dinosaurs survived, why would they not re-establish themselves in
their old niches? The African mammal fossil record shows many lineages
filling in for sauropods, elephants being key among them. If sauropods were
successful enough to survive the KPG, there is little reason to suggest
that they weren’t successful enough to expand, especially considering
that elephants and other groups were able to do so.
Sauropods were almost certainly ecosystem engineers,
manually reshaping ecosystems to their preference, with plants and
animals evolving to fit these patterns, both behaviourally and
anatomically - for an example of this look at the specialized
communities that form around elephants, even within their footprints (Remmers et al., 2016) and dung (Campos-Arceiz, 2009) - there's even a cryptid for the latter!. Sauropod equivalents are absent both within the fossil record and during the present day. The absence of dinosaurs is further attested to by the composition of post KPG forests (Weaver et al., 2025), where the lack of big herbivores creating clearings caused forests to grow denser and a shift in seed sizes to account for this increased density (Doughty et al., 2025). African fossil flora fits these patterns after the KPG.
If a sauropod survived, we'd expect to see evidence of their persistence in the mammal and floral fossil records. We don't, therefore we are as close to certain as we can be that there were no sauropods present at this time. The "as close to certain" verbage is more of a safety net than anything, I'd personally say that this is 100% the case.
But What About The Coelacanth?
But what about the coelacanth? Despite not being a ray-finned fish, the coelacanth is a red herring, often mis-invoked to justify the survival of megafauna that lived in completely different circumstances.
The coelacanth is marginally relevant to cryptozoology as a whole. The coelacanth was ethnoknown to indigenous peoples prior to discovery, but this information was not documented prior to the actual discovery of a living specimen - it’s a cryptid that could’ve been but was not, there are thousands of examples across zoology. The coelacanth is a deep-sea fish, living in depths only regularly trawled by human beings; these ecosystems act as consistent refugium for older groups of animals and are frequently home to entirely endemic, one-off species - conditions quite different than those on land. The coelacanth’s role is restricted to an early historical victory and a popular communication point to convey cryptozoological concepts - not as a way to say there are living dinosaurs.
Furthermore, like the incomplete nature of the fossil record, the
vastness of the ocean and its secrets are often blindly used to thwart
the discrediting of outlandish ideas. While the ocean remains
underexplored, it is not unexplored, we have the general gist
of what is going on, especially in regards to the presence or lack
thereof of prehistoric survivors - I’ll
use living mosasaurs as an example. The absence of these squamates can be demonstrated by more direct comparisons of the two groups, though a bit of fossil adequacy does help seal the deal.
Starting with comparisons - the coelacanth is a fish. The fish fossil record consists of small, isolated elements
or beautiful, fully-preserved lagerstätte specimens, with basically no in-between. The most common
fish fossils found are otoliths, the calcified remains of the inner ear;
alongside teeth, otoliths are the most durable hard structures in a
fish’s body. Actual bones such as vertebrae, skull pieces, or fin rays
are often consumed, swept away, or otherwise significantly damaged
before they can fossilize. Otoliths are six per fish, generally quite small, and hard to spot and often difficult to properly assign. Mosasaurs have no such issue - they have dense, large, heavy bones which are quite visibly different from any of the dominant marine groups of the Cenozoic.
Coelacanths are also a group that were previously ecologically
diverse but are currently ecologically conservative - the majority of
Mesozoic coelacanths lived in freshwater, brackish, or shallow saltwater
ecosystems. The best attested to fossil coelacanth lineages, all of
which are now extinct, lived primarily in these habitats. The record of
deep-sea coelacanths, and most deep-sea fish in general is
near-nonexistent. With this in mind it is very easy to see why they were
considered extinct. Mosasaurs, by virtue of being air-breathers, face
no such deep-sea bias. Extant coelacanths are deep-sea carnivores eating
small prey. Mosasaurs occupied a variety of niches, the most prominent
being carnivores consuming large fish and marine reptiles, or
durophagous predators consuming benthic prey. Massive, bottom-up marine ecosystem collapse (D'hondt, 2005)
saw the extinction of these prey sources for both categories of
mosasaurs. In their place evolved the predatory cetaceans, pinnipeds,
penguins, plotopterids, auks, and megatooth sharks - surely, any
mosasaurs would have inhibited these groups? The presence of these groups and the lack of evidence for mosasaur competition shuts the book - adequacy shows its usefulness again.
With coelacanths, it is quite clear how they escaped the fossil
record. This is not the case with mosasaurs, much less
terrestrial dinosaurs or other such animals. Comparisons should be apt and adequacy should be used.
Of course, this is not to say there are no likely prehistoric survivors. Using a list modified from Darren Naish, let's look at some more recent rediscoveries.
- Bush dog, Speothos venaticus: named as a fossil in 1839
and first described in living form in 1843. The same person, Danish
naturalist Peter Wilhelm Lund, described both the fossil and living
animals, but failed to realise they were the same thing: he named the
living animals Icticyon, and this name was for used for Speothos until well into the 20th century.
- Mountain pygmy possum, Burramys parvus: described from Pleistocene owl pellets in 1896 but found alive in a ski lodge in the Australian Alps in 1966.
- Chacoan peccary, Catagonus wagneri: named as a fossil in 1930, and found alive in 1974.
- Bulmer’s fruit bat, Aproteles bulmerae: described as a fossil in 1977 and reported from modern-day bones in 1980, then feared extinct, but since rediscovered alive.
- Laotian rock rat, Laonastes aenigmamus: last representative of a Miocene lineage, found in a Laotian meat market.
- Paulamys naso: Described as Floresomys from fossil material in 1981, but the genus was found to be preoccupied. A single live individual was reported in 1991.
What you'll notice is that these are all recent (Miocene onwards) and live in very dense habitats prone to endemism such as islands and jungles. These are the conditions in which our prehistoric survivors of the future are likely to be found - the veo may indeed be the giant Javan pangolin and I personally haven't counted Homo floresiensis out just yet. Maybe the mapinguari is indeed the last of the ground sloths. To assess the plausibility of these you'd have to undertake some detailed research - a paper on Homo floresiensis exists but remains unpublished. These examples, however, constitute better points of comparison for prehistoric survivors. There was little reason to count these species out at all, so maybe their rediscovery isn't too surprising...
The Prehistoric Survivor Paradigm
If the fossil record is adequate enough to suggest that most animals did truly go extinct, why are they invoked as prehistoric survivors so frequently? The answer lies in the inadequacy of resources consulted by or available to those who invoke them. This is true of Heuvelmans, Mackal, Sanderson, and other early cryptozoologists. Looking at sauropods within the context of the works they were invoked, gaps in understanding or resources available at the time become quite clear.
Mokele-mbembe has been suggested to potentially represent the last of the sauropod dinosaurs by multiple authors, key among them being Willy Ley, Bernard Heuvelmans, and Roy Mackal. It should be stated that Mackal and Heuvelmans did not readily consider a sauropod to be the most likely candidate for Mokele. The authors were writing from the 1940’s to late 1980’s - the Alvarez hypothesis based on a global iridium layer was first published in 1980 and the actual Chicxulub crater was first formally published on in 1991, with the potential for meteor impact (including prior knowledge of the crater) remaining extremely niche until the 1991 paper. Immediately prior to Ley’s first publication on Mokele-Mbembe, it was suggested that dinosaurs went extinct due to diminishing brain size and shortly before Heuvelmans finished On The Track, it was proposed that elevated temperatures prevented dinosaurs from producing sperm (see Benton 1990). The understanding of the extinction of the dinosaurs was long based on incomplete data leading to uncertainties about the actual process of their extinction. Furthermore, popular depictions of sauropods matched certain aspects of Mokele-mbembe’s description - the sluggish, swamp-dwelling Knightian Brontosaurus was still commonplace well into the 1940s (see Taylor 2010), a key example of the prevalent idea that dinosaurs were evolutionary dead ends. Both Heuvelmans’ Les dernies dragons d’Afrique and Mackal’s A Living Dinosaur? feature tail-dragging sauropods on their cover. Of course, by the time these books were published Bakker had already published his revolutionary article The Superiority Of Dinosaurs, being key in getting sauropods out of the swamps.
So, as is clear - these identities were proposed in a generally tumultuous time in dinosaur research, fueled heavily by popular media depictions, and persisted onwards as science started to render them outdated. The adoption of a generic sauropod identity by creationists, spread to a new audience by MonsterQuest is just as anachronistic as a genuine living sauropod would be.
This is what Darren Naish called the Prehistoric Survivors
Paradigm - the idea that in their search to assign known identities to
folkloric concepts, people mis-invoke extinct animals based on their
portrayals in popular culture, portrayals which rarely match the actual
scientific knowledge or the folkloric knowledge they’re seeking to
explain. I again encourage you to read his paper on the subject, linked
above, for a thorough explanation of this idea.
Of course the internet has exposed people to a variety of
previously obscure prehistoric animals and rather up-to-date depictions
of them, something only just beginning when Naish wrote his paper. This is not a perfect remedy to the PSP but oftentimes enthusiasts have a solid
understanding of depiction accuracy. The issue of failing to understand
paleoecology and the context in which these animals lived and died is
still quite evident as this information is rarely published on and
obscure, understudied single-line proposals in papers are often
uncritically circulated. It'd be interesting to study the effects of
this on recent proposals, I've noticed Karl Shuker has gotten a lot
wackier as time goes on.
Inadequate Identities
Assigning an identity to a cryptid is, in itself, often
problematic. The over-assignment of specimens was a long-standing issue
in paleontology as well, critiqued by David Good (Good, 1988).
Good stated:
“Placement of either paleontological or neontological material into taxa through mere similarity to known groups and without sound phylogenetic evidence has been a common practice, especially where fragmentary material with a limited number of observable characters is involved, and many groups are probably laden with such specimens. Unfortunately, this state of affairs often obscures analyses of evolution and biogeography with unsupported, and probably often false, information. There has often been a tendency in the past among those working with fragmentary material to feel compelled to identify specimens to the same taxonomic level possible among more complete forms. However, it cannot be denied that fragmentary material often does not contain as much information, and it must be realized that there is nothing wrong with classifying a specimen only to the level of genus or family or even class, if there is insufficient information available to do otherwise. In the case of fossils, if the material represents the ancestor of a modern group, this is all that will ever be possible, even given complete, rather than fragmentary, information. I propose that works describing and naming fragmentary materials will be greatly improved if an attempt is first made to demonstrate that the materials have the diagnostic features of the groups to which they are referred.”
When relying on eyewitness testimony, the parallels become obvious - without clear, independently verifiable, accurately identified features (i.e. not what you’d get from eyewitness testimony), it’s very difficult and very unnecessary to try and identify most cryptids; it’s more parsimonious to offer no explanation at all. The arguments above show why identifying modern cryptids with prehistoric survivors is often flawed and justified by misconceptions.
Conclusion
Citations
Benton, M. J. 1990. Scientific methodologies in collision: the history of the study of the extinction of the dinosaurs. Evolutionary Biology, 24
Bertrand, Ornella C., et al. “Brawn before Brains in Placental Mammals after the End-Cretaceous Extinction.” Science, vol. 376, no. 6588, Apr. 2022
Campos-Arceiz, Ahimsa. “Shit Happens (to Be Useful)! Use of Elephant Dung as Habitat by Amphibians.” Biotropica, vol. 41, no. 4, 19 May 2009
D’Hondt, Steven. “Consequences of the Cretaceous/Paleogene Mass Extinction for Marine Ecosystems.” Annual Review of Ecology, Evolution, and Systematics, vol. 36, no. 1, Dec. 2005
Doughty, Christopher E, et al. “Ecosystem Engineers Alter the Evolution of Seed Size by Impacting Fertility and the Understory Light Environment.” Palaeontology, vol. 68, no. 1, 1 Jan. 2025
Good, David A. “The Phylogenetic Position of Fossils Assigned to the Gerrhonotinae (Squamata: Anguidae).” Journal of Vertebrate Paleontology, vol. 8, no. 2, 22 June 1988
Lucas, Spencer G. “Paleocene Non-Avian Dinosaurs.” Italian Journal of Geosciences, vol. 144, no. 2, June 2025
Remmers, Wolfram, et al. “Elephant (Loxodonta Africana) Footprints as Habitat for Aquatic Macroinvertebrate Communities in Kibale National Park, South-West Uganda.” African Journal of Ecology, vol. 55, no. 3, 23 Aug. 2016
Taylor, Michael P. “Sauropod Dinosaur Research: A Historical Review.” Geological Society, London, Special Publications, vol. 343, no. 1, 2010
Weaver, Lucas N, et al. “Dinosaur Extinction Can Explain Continental Facies Shifts at the Cretaceous-Paleogene Boundary.” Communications Earth & Environment, vol. 6, no. 1, 15 Sept. 2025
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