In the 1600s, the specimen of a curious long-necked seal emerged. It could explain tall stories of sea serpents – if only it hadn't been mislaid

Could the long-necked seal specimen explain stories such as the Loch Ness monster? (Image: Everett Collection/Rex Features) A 1750 illustration of the mysterious seal (Image: Royal Society)

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Despite centuries of alleged sightings, no Loch Ness monsters or sea serpents have ever been found. But in the 1600s, the specimen of a curious long-necked creature emerged that could explain where such aquatic tall tales may have originated – if only it hadn’t been mislaid.

In the late 17th century, the botanist Nehemiah Grew published a catalogue of oddities held by the Royal Society in London. The book, called Musaeum regalis societatis, contains the first scientific description of a skin belonging to an unusual seal. He writes: “Wherein he principally differs, is the length of his neck; for, from his nose-end to his fore-feet, and from thence to his tail, are the same measure.” By contrast, most seal necks are only about a half the length of their lower body. In 1751, Grew’s description was cited by James Parsons in the Royal Society journal Philosophical Transactions (vol 47, p 109). Parsons included it in his list of known species.

Nobody has seen the skin since, and no further specimens have emerged. Could long-necked seals really exist? The idea persists but is now relegated to cryptozoology, the search for semi-mythical species. Cryptozoologists argue that many legendary creatures have actually existed and point to the colossal squid or king cheetah as examples.

Lurking monsters

Among the most enduring mythical creatures are “sea serpents”. The Loch Ness monster is a land-locked example, but most claims are marine. One popular idea is that such animals are plesiosaurs: long-necked marine reptiles that died out 65 million years ago. The idea doesn’t stand up. For one, they could not lift their heads into the swan-like pose attributed to Nessie. And while other creatures thought to be long-extinct have been found lurking in the oceans today – such as the coelacanth fish – it’s unlikely the plesiosaur would be absent from the fossil record for 65 million years.

In 1892, the Dutch zoologist Anthonie Cornelis Oudemans argued in his book The Great Sea-serpent that such monsters were long-necked seals. The idea met with a chilly reception, but it was revived in 1968 by cryptozoologist Bernard Heuvelmans in his book In the Wake of the Sea-serpents.

While the existence of a long-necked seal today is speculative at best, there is some circumstantial evidence. In 2009, Michael Woodley, then of Royal Holloway, University of London and colleagues estimated that up to 15 species of pinnipeds, the animal group that includes seals and walruses, might remain undiscovered (Historical Biology, vol 20, p 225).

Woodley also points out that no living animal has taken over the long-necked grazer niche vacated by the plesiosaurs. And fossils of Miocene seals called Acrophoca – a possible ancestor – have proportionally longer necks than seals today (Palaeontology, vol 45, p 821).

No new pinnipeds have been discovered since 1953. So if a new species emerged, it would be a big deal. The lack of confirmed sightings suggests the species wouldn’t need to surface as frequently as other seals to breathe or breed. Of course, it could also mean it doesn’t exist at all. If Grew’s seal skin turned up though, cryptozoologists would be delighted.