The other day I showcased some art and text from the upcoming Cryptozoologicon, a book currently being put together by John Conway, C. M. Kosemen and myself and scheduled to appear later this year. Today I want to do the same thing.

This time, we’re going to look at the section on Megalodon, the Megatooth shark. My, how timely! (read on to see why). Sharks aren’t tetrapods (and hence aren’t ordinarily part of the Tet Zoo remit) but, what the hey, I’ve broken the rules before, I’ll break them again here.

Hello there, Megalodon!

The seas are full of monsters. Or, they are according to some of the cryptozoological literature, anyway. As if numerous giant, as-yet-undiscovered marine mammals and reptiles and absurdly super-sized cephalopods aren’t enough, cryptozoologists have also advocated the possibility that Carcharocles megalodon – popularly dubbed Megalodon or the Megatooth shark – is not just known from the fossil record, but that it might also survive to the present. Megatooth sharks are, unsurprisingly, known almost entirely from their enormous teeth, the largest specimens of which are an incredible 16.8 cm long. Vertebral centra of Megatooth sharks are known in addition to teeth, but that’s it, and – unsurprisingly – there has been much tendency to over-estimate the size of this giant. A total conservative length of approximately 15.9 m was extrapolated by Gottfried et al. (1996) but they also calculated total lengths of as much as 20 m for some individuals. These authors also suggested that C. megalodon had a deeper, blockier skull than the Great white shark Carcharodon carcharias.

While C. megalodon is often imagined to be a giant version of the modern Great white, it may only be distantly related to it. In fact, some experts allocate these sharks to entirely different sections of the shark family tree and at least three different technical names are used for C. megalodon (Carcharocles megalodon, Carcharodon megalodon and Megaselachus megalodon). Regardless, good evidence shows that Megalodon was ecologically similar to the Great white, albeit much larger and more powerful.

Bite marks preserved on bones show that Megatooth sharks fed regularly on dolphins and baleen whales, though it remains unknown whether the bite marks we know of represent scavenging or the hunting of live cetaceans. Megatooth shark teeth are frequently found in areas where the remains of baleen whales are common (Purdy 1996), and both shared the same habitat.

So far as we can tell from the fossil record, C. megalodon died out some time during the early part of the Pleistocene, presumably as cooling conditions reduced its preferred habitat [UPDATE: be sure to read comment # 6 below. A Pleistocene extinction date may be too recent!]. And here we come to the cryptozoological case for Megalodon survival: the sort of thing discussed in various popular books and magazine articles about mystery creatures (Shuker 1991, 1995, 1997). Alleged Megalodon survival was examined by Roesch (1998) who basically concluded that there is no reason to take alleged Megalodon survival at all seriously. We agree with his conclusions.

A very small number of stories and alleged eyewitness encounters essentially make up the core of the case for Megalodon survival. In the best known and most oft-repeated, Australian naturalist David Stead described a tale related to him in 1918 by Australian crayfish fishermen in which a gargantuan and ghostly-white shark, perhaps 90 m long, emerged from the deep to take their crayfish pots, mooring lines and whatever else was attached. This story has sometimes been taken semi-seriously, partly because Stead (a reputable and respected writer and researcher, greatly experienced in ichthyology) explained the reliable nature of his (anonymous) sources. Alas, a fishermens’ tale about a white monster shark that eats crayfish pots is hardly a reputable source and the account is an entertaining anecdote that we cannot regard as evidence of any sort.

Two other giant shark sightings claimed to be possible Megalodon sightings are clearly poor descriptions of Whale sharks Rhincodon typus. There’s also a story from the 1960s (recounted in a popular 1978 book) about a giant white shark, longer than 80 m, spoken of by a ship’s anonymous crew. So, we’re left with stories: scary stories of the sort that seafarers enjoy telling other people when back on land. Indeed, the case for Megalodon’s survival is so weak that it isn’t really “a case”.

Megalodon survival is also supposedly supported by the discovery of teeth that are not fossilised or are supposedly coated in such a thin layer of manganese dioxide that they must surely be young, in geological terms. In fact, the teeth (the most famous of which were dredged up by the Challenger expedition of the 1870s) have been misinterpreted and there’s no reason to think that they’re geologically young, let alone modern (Roesch 1998).

The speculative part

What, now, of our speculative parallel universe, where all the cryptids are real and megatooth sharks still swim the oceans? Again, it would be difficult to say anything speculative about Megalodon that hasn’t already been said. In order that a giant, macropredatory, whale-eating shark might remain elusive and undocumented by biologists, it would have to be absurdly secretive, spending just about all of its time away from the surface, away from vessels, and away from the coastal regions where it would surely be discovered. It must, therefore, be a deepwater animal that specialises on prey that it can reliably encounter at depth, and it must have switched to this prey base some time since the Pliocene or start of the Pleistocene. [The brilliant image below shows a modern-day Megalodon, by John Conway. For the full-size version go here.]

This evolutionary shift has occurred at breakneck speed: while a new, slower growth regime and occupation of an otherwise unexploited ecological niche have encouraged Megalodon to become substantially larger than the 20 m or so achieved by its ancestors, it has not yet become fully abyssal like other deepwater sharks and still visits the surface to eat crayfish pots and small fishing vessels on occasion. We would have to imagine the new, abyssal Megalodon – arguably different enough to warrant classification as the new species Carcharocles modernicus – to haunt deepsea canyons and places where whales and elephant seals and so on are regular visitors.

Previously, it was Mermaids. Discovery wins again… (read: loses)

Of course, our coverage here of Megalodon is extremely well timed since Discovery have just screened a notorious pseudo-documentary in which they seemingly try and trick naïve viewers into thinking that Megalodon is still extant, and that there’s evidence for this possibility in the way of assorted photos and other lines of evidence [disclaimer: at the time of writing, I haven’t seen said TV show]. The idea that a once-reputable documentary-based TV channel might broadcast such a show is incredible, even in the wake of the two ridiculous mermaid shows screened by the same channel over the past few years.

So far I’ve heard nothing but dissatisfaction and anger directed at Discovery, with some people even demanding an apology. Remember that their Megalodon show isn’t presented as mere entertainment a la Sharknado, but as a documentary that’s screened adjacent to genuine documentaries about real sharks, their biology, their world, and their plight. It will surely be interpreted as real by a large percentage of its viewers. As shown (above) by this screen-grab from Discovery’s facebook page, people aren’t happy (at least, people who leave comments on the page... the disturbingly high number of 'likes' shows how popular such garbage is). If any of this energy can be converted to help benefit real sharks in the real world, we can be happy that something good has come of it.

The Cryptozoologicon – by John Conway, C. M. Kosemen and Darren Naish – is due out later in 2013 and will be published by Irregular Books. Follow @IrregularBooks on twitter.

Refs - -

Gottfried, M. D., Compagno, L. J. V. & Bowman, S. C. 1996. Size and skeletal anatomy of the giant “megatooth” shark Carcharodon megalodon. In Klimley, A. P. & Ainley, D. G. (eds) Great White Sharks: The Biology of Carcharodon carcharias. Academic Press (San Diego), pp. 55-66.

Purdy, R. W. 1996. Paleoecology of fossil white sharks. In Klimley, A. P. & Ainley, D. G. (eds) Great White Sharks: The Biology of Carcharodon carcharias. Academic Press (San Diego), pp. 67-78.

Roesch, B. S. 1998. A critical evaluation of the supposed contemporary existence of Carcharodon megalodon. The Cryptozoology Review 3 (2), 14-24.

Shuker, K. P. N. 1991. The search for monster sharks. Fate 44 (3): 41-49.

- . 1995. In Search of Prehistoric Survivors. Blandford, London.

- . 1997. From Flying Toads to Snakes with Wings. Llewellyn Publications, St. Paul, Minnesota.