HOW A GIANT SNAKE BECAME A SPIKY SEASHELL – WELCOME TO THE MAUSOLEUM OF MONSTERS

One of several artworks by Swiss painter Henry Fuseli (1741-1825) with a cryptozoological connection – Reiter Von Riesenschlange Überfallen ('Horseman Attacked By A Giant Snake'); watercolour, painted in c.1800 (public domain)

In contrast to insidious and infamous zoological frauds such as Piltdown Man and the stuffed mermaids of Oriental origin, many cases of confused taxonomic classification have occurred not through deliberate, predetermined intentions to create non-existent creatures or to lure scientists along false trails, but instead via simple misidentifications. Nonetheless, the results have often been both unexpected and spectacular, but few more so than in the case of the giant venomous serpent of South America's Gran Chaco region. After all, how can such an ostensibly monstrous reptile transform into a spiky seashell of far more modest proportions and far less dangerous attributes?

As I now reveal here in ShukerNature, the story of this astonishing metamorphosis, though largely forgotten today, must surely rate as one of the most extraordinary (and embarrassing) incidents in the entire history of 20^th-Century zoology.

Gran Chaco location on map (public domain)

Deep within the most secluded realms of the mystery beast investigator's mind lies a dark and mournful cemetery, whose gates are for the most part firmly chained and heavily barred. Whenever his speculations and theories aspire to the grandiose and gothic, however, he is forced to tread the shadowy pathway leading to this most dreaded and dreadful of destinations - the mausoleum of monsters.

In this forsaken spot – within this cryptic catacomb of mythological mammalia, apocalyptic archosauria, and other fabulous fauna of every type - no ordinary assemblage of skeletons is ensconced. No, indeed. Here, amongst shattered dreams and mocking illusions, lie the hastily-jettisoned remains of those great zoological discoveries that were subsequently exposed as sorry misidentifications. A faux-pas phantasmagoria, whose forbidding presence within the annals of zoology serves as a stern warning to all cryptozoologists of the perils of premature pronouncement or imprudent identification. Let us tarry a while here, and examine one of its most dramatic examples.

A veritable mausoleum of monsters – an exquisite 19^th-Century engraving depicting some of the Victorian-age prehistoric animal sculptures of Crystal Palace created by English sculptor Benjamin Waterhouse Hawkins (1807-1894) (public domain)

In 1926, the Proceedings of the Royal Society of Edinburgh published a paper by Prof. Sir John Graham Kerr, at that time Regius Professor of Zoology at the University of Glasgow, in which he described a huge, curved poison fang belonging to a hitherto unknown genus and species of giant snake - which he formally named Bothrodon pridii (with Bothrodon translating as 'furrow-tooth').

Approximately 2.5 in long as measured along the outside of the curve, this fang was truly enormous.

Bothrodon pridii 'fang', pictured in 1926; scale in mm (public domain)

Indeed, as noted by now-retired mollusc expert David Heppell from the Royal Museum of Scotland who documented this specimen in The Conchologist's Newsletter (March 1966), it was roughly nine times longer than that of a 6-ft-long boomslang Dispholidus typus - one of the world's deadliest snakes.

Moreover, it even dwarfed the fangs of the Gaboon viper Bitis gabonica. Native to much of sub-Saharan Africa, this formidable serpent not only is the largest member of the genus Bitis and the world's heaviest species of any type of viperid, but also holds the record for the longest fangs of any known species of snake alive today – up to 2 in long.

Gaboon viper showing its huge fangs (© Brimac the 2^nd/Wikipedia CC BY 2.0 licence)

Accordingly, judging from the relative size of the fang, Prof. Kerr estimated that the total length of its venomous owner, Bothrodon pridii, could have approached 60 ft or so.

Truly a monster, in every sense of the word!

Prof. Sir John Graham Kerr (© T & R Annan & Sons Ltd/Wikipedia CC BY 4.0 licence)

The poison fang had been obtained by one of Kerr's friends, missionary Andrew Pride (after whom Kerr had named this outsized ophidian) from the Gran Chaco's silt-like deposits, which dated back no further than the Pleistocene epoch (2.5 million to 11,700 years ago). Despite a prolonged, thorough search of this locality by Pride for this mega-snake's skeletal remains, however, none were found.

In his paper Kerr concisely described the fang's appearance, including the prominent poison groove running all along its apparent external face, as well as the two narrow parallel stripes, dark-brown in colour, that lay along the distal (terminal) portion of its length. He also discussed the possible phylogenetic relationships of Bothrodon pridii itself, by comparing its fang's morphology with that of contemporary snake species.

The boomslang, an opisthoglyphan snake, depicted in 1838 (public domain)

From these studies, Kerr concluded that the fang most closely resembled those of the opisthoglyphans. This is a group of rear-fanged colubrid snakes that include the boomslang, and which point the way towards the more highly-evolved present-day venomous snakes. In addition, Kerr deduced from the fang's peculiar hook-like shape that, rather than functioning as a striking fang, it most probably served to hold the prey stationary whilst its poison entered the wounds produced by the snake's other teeth in the prey's flesh.

Sherlock Holmes would certainly have approved - because Kerr's paper demonstrated most effectively the considerable amount of information concerning an entire organism (be it serpent or sapient!) that could be obtained by meticulous analysis of only a single component of that organism. Or so it seemed...

Reconstruction of the giant ground sloth Megatherium (public domain) alongside a fossil skeleton of it at London's Natural History Museum (© Dr Karl Shuker)

Kerr duly presented this unique fang to the Hunterian Museum of the University of Glasgow, and in 1933 a cast of it was displayed alongside a label stating that Bothrodon may have fed upon cumbersome plains-dwelling creatures such as the giant ground sloth Megatherium.

Conversely, noted herpetologist Dr Raymond Ditmars suggested small mammals as likely prey in his classic book Snakes of the World (1931).

Dr Raymond Ditmars (public domain)

Nevertheless, Ditmars was palpably impressed by Kerr's discovery and documentation of Bothrodon, exclaiming in his snake book:

It was during the preparation of this manuscript that the author received the greatest surprise in the many years he has studied the serpent clan – and it related to a rear-fanged snake.

Its possible stature also greatly excited Ditmars:

As the poison-conducting teeth of the rear-fanged snakes are short in proportion to the body length, the size of this monster is open to thrilling conjecture...Indeed the thought it inspires rather dulls the conjectural image of that dinosaurian star, Tyrannosaurus, whose races passed away ages before this mammoth Bothrodon prowled the soil.

I'm not quite sure how a limbless creature can be said to prowl; but in any event, as a serpent of substance Bothrodon remained unchallenged – until 1939, that is, when it was unceremoniously dethroned, disgraced, and, worst of all, exposed as nothing more than a snail in snake's similitude!

Chiragra spider conch's shell, underside (© Udo Schmidt/Wikipedia CC BY-SA 2.0 licence)

For Dr W. Quenstedt, after closely examining a coloured cast of the fang sent to the University of Berlin's Paleontological Museum by Prof. Kerr, recognised the specimen's true identity. It was one of those six curved projections, long and groove-bearing, that fringe the large shell aperture of Lambis [now Harpago] chiragra, the Chiragra spider conch - a large and ornate, modern-day species of Indo-Pacific gastropod mollusc! Every feature of the 'fang' confirmed this identity – its size, shape, long groove, brown stripes. There could be no mistake – Bothrodon pridii was no more.

To be fair, however, Kerr's misidentification is not as surprising as it may seem on first sight. After all, he could hardly have been expected to anticipate the discovery within the deposits of Paraguay's Gran Chaco of a shell fragment from a gastropod normally inhabiting the Indo-Pacific oceans.

Bothrodon 'fang' and shell projection from Chiragra spider conch's shell (public domain)

Indeed, this one aspect of Bothrodon's bizarre history remains totally unexplained and seemingly inexplicable even today. How could a section of shell from a modern-day Indo-Pacific mollusc have been obtained in Gran Chaco? David Heppell noted that there is no question that Gran Chaco was the locality involved. Thus, as he remarked, the discovery can be explained only by way of some human introduction.

Notwithstanding this, the survival of Bothrodon pridii within the zoological literature on taxonomic synonyms serves as a stark reminder of just how easily and how far one can travel along the wrong track after having once set foot upon it. Certainly, although many weird metamorphoses have been documented from the animal kingdom, few can surely compare with the transformation of a giant snake into a spiky seashell!

Chiragra spider conch's shell, upper side (© James St John/Wikipedia CC BY 2.0 licence)

As a curious footnote (assuming of course that anything concerning snakes can possess a foot!): even though the re-identification of the Bothrodon 'fang' as a prong from the shell of a Chiragra spider conch was swiftly and fully accepted by the herpetological community following Quenstedt's dramatic denouement in 1939, it is possible that Kerr himself was not so quick to accept this embarrassing revelation.

The reason why I suggest this is that while browsing very recently through Kerr's book A Naturalist in Gran Chaco, first published in 1950 and chronicling the zoological expedition that he mounted during the late 1890s to this vast semi-arid region of southern South America (overlapping northwestern Bolivia, western Paraguay, northern Argentina, and a small portion of southwestern Brazil), I was very surprised to find that although he included just over a page devoted to the Bothrodon specimen's discovery and his studies of it, he made no mention whatsoever of its molluscan re-identification. Equally, however, I can find no mention anywhere of his ever having publicly discounted or disputed this latter taxonomic reassignment of it.

Hardback first edition of Sir John Graham Kerr's book A Naturalist in Gran Chaco (© Sir John Graham Kerr estate/Cambridge University Press – reproduced here on a strictly non-commercial Fair Use basis only, for educational/review purposes)

So how can we explain this very curious, and conspicuous, absence in Kerr's book, which was first published more than a decade after Quenstedt's fateful, published declaration? As Kerr died just seven years later, in 1957, it is likely that we shall never be able to answer this highly intriguing question with any degree of certainty.

Taxonomically speaking, therefore, Bothrodon pridii may indeed be long dead and buried within the mausoleum of monsters, but perhaps its mystery is not entirely extinguished after all.

My own close encounter with a giant snake… - a magnificent life-sized sculpture by Tim Johnman of a reticulated python at Taronga Zoo in Sydney, Australia, which I visited in 2006 (© Dr Karl Shuker)