Monsters, Sea-Monks, and Mermaids: Strange Creatures from the Sea from Antiquity to the Modern Age

This blogpost previously appeared on the Leiden Arts in Society Blog. The text is an extract from the catalogue of the exhibition ‘Fish & Fiction‘ which is currently on view at the Leiden University Library. The exhibition  is a collaboration between the library and the LUCAS project ‘A New History of Fishes. A long-term approach to fishes in science and culture, 1550-1880’. The catalogue: ‘Fish & Fiction. Aquatic Animals between Science and Imagination (1500–1900)’ can be purchased at the reception desk of the Leiden University Library.


Throughout the centuries, sea-monsters have featured not only in stories, legend and art, but also in the study of nature. In Antiquity, scholars theorised that water generated more monstrosities than any other environment. Medieval and Early Modern scholars did not exclude the possibility that sea-monsters exist, and collected rather than contradicted reported sightings. As a consequence they helped spread stories about monstrosities from the sea and contributed to a culture in which such monsters were omnipresent. Medieval and Early Modern depictions of strange creatures from the sea can be found as decorative elements on maps and in works recording folklore, man-made monsters were included in Early Modern collections of naturalia, and sea-monsters were described in scholarly works, even up until the Modern period. Many of these creatures and their characteristics were based on descriptions from Antiquity, while at the same time new monsters were introduced.


The Nature of Monsters

In Antiquity nature in general was seen as flexible and capable of producing any variety of creatures. This was believed to be particularly true for aquatic environments. The Roman naturalist Pliny the Elder stated that monstrosities form most easily in water, due to its liquid nature and the amount of nutrients it contains. Later on, Christian authors presented this plasticity of nature as the consequence of divine omnipotence. As a result, monsters were on the one hand seen as natural phenomena and on the other often interpreted as divine signs. For example, several sixteenth century scholars describe a ‘sea-monk’, a creature with a tonsured head and scaly robes. This was interpreted by the religious author and counter-reformer Aegidius Albertinus (1560–1620) as a divine expression of dissatisfaction with the hypocrisy of the clergy, while the scholar Paracelsus (1493–1541) provided a natural explanation for its existence by stating the creature must be the offspring of a fish and a drowned monk.

Monachus marinus, in Conrad Gessner, Historiae animalium liber IIII qui est de piscium et aquatilium animantium natura, Zürich, C. Froschauer, 1558, p. 519. [Leiden University Library, 665 A 7]


Terrestrial Counterparts

Like the sea-monk, many aquatic monsters resembled something or someone we might find on land. Since Antiquity it had been assumed that aquatic creatures often took the form of a, natural or artificial, terrestrial counterpart. As evidence of this principle, classical authors referred to creatures such as the sea-cucumber, the swordfish, and the sawfish. Classical mythology also featured a range of aquatic deities with human upper bodies and the lower body of a fish, such as Nereids, as well as creatures which were part terrestrial animal, such as the hippocampus, with the upper body of a horse and lower body of a fish. Descriptions and depictions of sea-monsters from the Middle Ages and the Early Modern era show us similar mixtures of aquatic and terrestrial features. The popular late fifteenth century natural history encyclopedia Hortus Sanitatis for example, presents to us a range of sea-creatures with terrestrial characteristics. The illustration shows a page from a 1536 German edition, Gart der Gesundheit, which bears depictions of a sea-cow with the upper body of a cow and lower body of a fish, a bird with a fishtail, and several Nereids.

Various monsters and mythical creatures, in Gart der Gesundheit zu latein Hortus Sanitatis : Sagt in vier Bücheren von Vierfüszsigen vnd Krichenden, Vöglen vnd den Fliegenden, Vischen vnd Schwimmenden thieren, dem Edlen Gesteyn vnd allem so in den Aderen der erden wachsen ist, Strasbourg, M. Apiarius, 1536, fo. XCII. [Leiden University Library, 1370 B 15]



While there was much continuity in the way sea-monsters were portrayed and perceived, new developments also took place. While mermaids were unknown in Antiquity, sightings of these creatures were reported with some regularity by Medieval and Early Modern authors. A page-wide depiction in a work on monstrosities, Monstrorum historia (1642) by the first professor of natural sciences at the University of Bologna and founder of its botanical garden, Ulysse Aldrovandi (1522–1605), shows us what such creatures were believed to look like. In appearance these much resemble the Nereids from Antiquity, which were believed to be friendly and keen to help sailors in distress. In this, they resemble the benevolent aquatic fairies native to western European folklore. By contrast, mermaids were believed to be dangerous and seductive creatures that shipwreck vessels and lead sailors to their doom. In this, they resemble another creature from classical mythology, the siren. These birdlike creatures with human faces were believed to enchant sailors with their singing in order to cause them harm. During the Middle Ages, elements of sirens, sea nymphs, and aquatic fairies, were combined in popular imagination to form the mermaid.

Monstra Niliaca, in Ulisse Aldrovandi, Opera omnia. XI Monstrorum historia cum paralipomenis historiae omnium animalium, Bologna, N. Tebaldini, 1642, p. 354. [Leiden University Library, 655 A 13]


Monstrous Whales

While monstrous whales had been described since Antiquity, the sixteenth century generated an unprecedented variety of such creatures. Little knowledge on whales had been gathered during Antiquity and the Middle Ages, and often monstrous proportions and strength were attributed to these animals. For unknown reasons, in the second half of the sixteenth century whales beached more frequently than usual on European shores. Around the same time whaling increased. As a result, knowledge expanded, but up until then accurate depictions and descriptions were scarce and the line between whale and monster remained difficult to draw. The Swedish chronicler Olaus Magnus published depictions of monstrous whales based on folklore on his 1539 map of Scandinavia Carta marina et descriptio septentrionalium terrarium and in his 1555 chronic of Scandinavia Historia de gentibus septentrionalibus, which became instantly popularThe creatures shown on the map of Iceland from the Antwerp cartographer Abraham Ortelius’s atlas Theatrum orbis terrarum (1570) are based on Magnus’s monsters. The map shows ten monstrous whales, with claws that resemble those of terrestrial animals.

Islandia, in Abraham Ortelius, Theatrum orbis terrarum, Antwerp, s.n., 1570. [Leiden University Library, COLLBN Atlas 43: 1]


Man-Made Monsters

Basilisks were first described in Antiquity as dangerous serpents and acquired new characteristics in later centuries. By the late Middle Ages they had become winged monsters, born as the result of a bizarre sequence of events, which could kill anyone by looking at them. During the Early Modern period basilisk-like monsters were manufactured out of rays. The scholar Ulysse Aldrovandi describes two such creations as basilisks, while others are described as winged snakes or dragons. In 1558 the Swiss scholar Conrad Gessner (1516–1565) explained, in his encyclopaedia of animals Historia animalium, how these were made, by twisting, cutting and drying a ray. He complains that the man-made monsters were passed off as real to impress the masses and were often exhibited in apothecary shops. However, they were also part of scholarly naturalia collections. Aldrovandi collected several and described no fewer than five in his Serpentum et draconum historiae (1640) and De piscibus et de cetis (1623).

Winged snake, in Conrad Gessner, Nomenclator aquatilium animantium icones animalium aquitilium in mari et dulcibus aquis degentium, Zürich, C. Froschauer, 1560, p. 139. [Leiden University Library, 665 A 9]


Draco ex Raia effictus, in Ulysse Aldrovandi, Opera omnia. X: Serpentum et draconum historiae libri duo, Bologna, N. Tebaldini 1640, p. 315. [Leiden University Library, 655 A 12]


The Sea-Unicorn and the Narwhal

First reports of the unicorn date back to the fourth century BC, when the scholar Ctesias described a one-horned horse which he had heard about. The legend subsequently spread through the work of Aristotle and other scholars. In addition, a mistranslation in the bible gave the impression that the unicorn was mentioned in the Old Testament. Scholars of the Middle Ages and first half of the Early Modern period consequently had good reason to believe in unicorns. The assumption that animals on land have aquatic counterparts, meant that the existence of a sea-unicorn was also widely accepted. Believed to neutralise poison, what was sold as unicorn horn fetched exorbitant prices. In the sixteenth century scholars began to suspect that these ‘horns’ were in fact narwhal teeth. The collector Ole Worm published a treaty on this subject in 1638. The discovery quickly became common knowledge and inspired the depiction from Pierre Pomet’s Histoire generale des drogues, published in 1694, of a sea-unicorn and narwhal side by side. However, rather than diminishing belief in the medical properties of the horns, this led many to belief that the narwhal was in fact the sea-unicorn. The last recorded use of unicorn horn in folk medicine took place in the nineteenth century.

Licorne de Mer, in Pierre Pomet, Histoire generale des drogues, traitant des plantes, des animaux, et des mineraux, Paris, J.-B. Loyson, etc.,1694, p. 78. [Museum Boerhaave Library, BOERH e 2459 a]


Modern Sea-Monsters

Certain sea-monsters have proved surprisingly durable. The depiction of a giant sea serpent published by the Dutch zoologist Anthonie Oudemans in 1892, is not unlike many depicted in mosaics from Antiquity or in books from the Middle Ages and Early Modern period. Towards the end of the nineteenth century sightings of this mythical creature were still reported with such regularity that Oudemans was able to collect nearly two hundred reports over the course of three years. Applying what is known as a crypto-zoological approach, in the absence of empirical evidence, Oudemans used the quantity of sightings as an argument that the giant sea serpent was an existing species. He proposed the scientific name Megophias megophias for the yet to be discovered creatureOudemans received a lukewarm reaction from the academic world, where both cryptozoology and the existence of sea-monsters were considered controversial. Nonetheless, The Great Sea Serpent was published by reputable academic publishers. As Oudemans pointed out, the fact that a sea-monster has not yet been discovered does not prove it does not exist.

The sea-monster, as Mr. C. Renard supposed to have seen it, in Anthonie Cornelis Oudemans, The great sea-serpent: An historical and critical treatise: With the reports of 187 appearances, Leiden, Brill etc. – London, Luzac & Co, 1892, p. 56. [Leiden University Library, 290 B 7]


© Sophia Hendrikx and Fishtories, 2018. Unauthorised use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Sophia Hendrikx and Fishtories with appropriate and specific direction to the original content.

Fantastic Beasts and How to Make Them (according to 16th-century instructions)




A Jenny Haniver made for the exhibtion ‘Fish and Fiction’. Image: Sophia Hendrikx



A Jenny Haniver in Conrad Gessner’s (1516-1565) Nomenclator aquatilium animantium, 1560. Image: Leiden University Library


TThis rather spectacular depiction dating from the sixteenth century, and the modern imitation based on it, are creations which are nowadays called Jenny Hanivers. A ray is cut, shaped and dried in order to make it look like a basilisk or a dragon. While it may sound unusual, these creations were produced on a rather large scale during the Early Modern period. The author of the above illustration, Conrad Gessner (1516-1565) tells us how this was done. His instructions inspired me to try this out, and after several failed attempts I now have dragons adorning my home and office. Before getting into the practical side of things though, let’s explore the historical background. What exactly is a Jenny Haniver?


Origin of the name

The name can be traced back to 1928, to a publication of the biologist Gilbert P. Whitley, who described how an acquaintance bought such a dried ray from an antique shop and wrote to him that, although he wasn’t a hundred percent sure, he thought the salesperson had called the object a ‘Jenny Haniver’. In fact, this name can be traced back no further than Whitley’s article, and may well originate there.


Conrad Gessner (image: sciencesourceimages) and his Nomenclator aquatilium animantium, 1560 (image: Leiden University Library).


What is a Jenny Haniver?

In his description of these objects, Gessner tells us that Jenny Hanivers were made to impress people and were passed off as real. Gessner, who lived from 1516 to 1565, was rather well informed himself. He published on a wide range of subjects, from philology and theology to medicine and natural history, and corresponded with scholars across Europe, one of which sent him the above depiction. Gessner reproduced it first in his encyclopaedic work on animals Historiae Animalium (1551-58), and two years later in an abridged version of the volume on fish, the Nomenclator Aquatilium Animantium (1560).

While Gessner was not the first to describe a Jenny Haniver, he was the first to explicitly describe it as a man-made object, and to explain how it was made. His instructions read as follows:

“In order to impress common people, apothecaries and others dry rays and twist their skeletons into all sorts of remarkable poses, making the animal look like a snake or a winged dragon. They twist the body, alter the shape of the head and mouth, and remove other parts or make them smaller. The lower part of the body is cut, and what remains is lifted, to make it look like the creature has wings.”


Image: seavoicenews


Why rays?

It isn’t hard to imagine how this is done. Rays already have a suggestive appearance which is fairly easy to manipulate. If we look at a ray from below, we may get the impression that a friendly face is staring back at us. In fact, this consists of the mouth and nostrils of the animal, the real eyes being located on top of the head. Taking advantage of this, many Jenny’s were made by turning the head upwards towards the observer. This is particularly clear in the here shown depiction from the work of the sixteenth century Italian scholar Ulysse Aldrovandi.


Jenny Haniver from Ulysse Aldovandi’s De piscibus, 1613. Image: Leiden University


Real or not?

Also in the more unusual Jenny Haniver from another sixteenth century work included below, the mouth and nostrils appear to form a face. Gessner refers to this depiction which was first published in 1551 by the French naturalist Pierre Belon (1517-1564) in his L’histoire naturelle des éstranges poissons marins. While this specimen still resembles a ray, a large portion of the wings was cut and the shape of the head radically altered. Although it appears he was well aware the depicted creature had been tampered with, Belon does not mention this in his description of the creature.


Jenny Haniver in Pierre Belon’s De aquatilibus, 1553. Image: Library of the United States Department of Agriculture, Cambridge (Mass.).


This approach is not unusual in descriptions of monstrous creatures of this period. While Gessner explicitly exposes his Jenny Haniver as a fraud, in his descriptions of other non-existent and marvellous creatures we find a similar duality. He writes for example, that so many sources claim these creatures exist, that he cannot deny the possibility. This way of phrasing it, of course suggests that Gessner himself is not entirely convinced. Similarly, Belon describes this Jenny Haniver alongside several descriptions of rays he had studied and dissected, suggesting that he knew what he was dealing with, but without explicitly saying it.



Belon’s depiction of a Jenny Haniver was copied by the earlier mentioned Ulysse Aldrovandi (1522-1605). Aldrovandi was professor at the University of Bologna and the founder of its botanical garden. He was also an ardent collector and accumulated over seven thousand naturalia and drawings of naturalia, including Jenny Hanivers. In his works on natural history he depicted five, showing us the great variety of Jenny Hanivers that were in circulation at the time.


Three Jenny Hanivers from Ulysse Aldovandi’s De piscibus, 1613. Image: john-howe


How to make them

So how does this work in practice? While Gessner indicates the ray should be shaped and dried, he does not clarify how this should be done. He does provide some instruction as to how it should be cut, but this takes some skill and practice, neither of which I had when I first tried to do this. Luckily for me, a member of our project group is a biologist turned historian of science, with years of experience dissecting animals. Robbert Striekwold quickly taught me how to cut and shape a fish, and as an amateur taxidermist, he was also able to advise me about taxidermy shops where I could buy the necessary equipment.

That part of the process mastered, now the Jenny’s had to be dried and kept in the desired posture during the process. Since there is no way of knowing how Gessner’s Jenny Haniver was dried, several methods had to be tested. Three seemed the most obvious, drying in the open air, and, in imitation of common methods of food preservation, slow heating and salting (scroll down for pictures and further information). In the end I dried several specimens in a mixture of different salts over the course of six weeks, using bags of salt to prop my ray up. This done, I varnished them and gave them glass eyes.



Image: Sophia Hendrikx


The specimen shown here was presented at the opening of the Fish & Fiction exhibition in Leiden, the Netherlands. Once the exhibition closes it will be added to the collection of the Naturalis Biodversity Centre. The rest of my growing collection of Jenny’s remain with me for now, and will possibly find more suitable homes in the future.



Image: Sophia Hendrikx


Further reading:

Sophia Hendrikx, Monsters, Sea-Monks, and Mermaids. Strange Creatures from the Sea from Antiquity to the Modern Age. In: Marlise Rijks, Paul J. Smith & Florike Egmond (editors), Fish & Fiction. Aquatic Animals between Science and Imagination (1500-1900). Leiden University, 2018.

Sophia Hendrikx, Monstrosities from the Sea. Taxonomy and tradition in Conrad Gessner’s (1516-1565) discussion of cetaceans and sea-monsters, Anthropozoologica 53 (11): 125-137.

Sophia Hendrikx, Het eerste en misschien ook wel het kleinste en mooiste boek over waterdieren. In: Hans Mulder en Erik Zevenhuizen (Red.), De natuur op papier. 175 jaar Artis Bibliotheek. Amsterdam, Athenaeum-Polak & Van Gennep, 2013.

Peter Dance, Animal frauds and fakes. Maidenhead, Berkshire, Sampson Low, 1976.

Pierre Belon, De aquatilibus. Paris, Charles Estienne, 1553.

Conrad Gesner, Historiae animalium liber IIII. Zurich, Christoph Froschauer, 1558.

Conrad Gesner, Nomenclator aquatilium animantium. Zurich, Christoph Froschauer, 1560.

Ulysse Aldrovandi, De piscibus. Bologna, Baptiste Bellagamba, 1613.

Ulysse Aldrovandi, Opera omnia. X: Serpentum et draconum historiae libri duo, Bologna, N. Tebaldini 1640.



Making a Jenny Haniver:



Image: Sophia Hendrikx

The first attempt, created by myself and Robbert, using a monkfish rather than a ray due to a mix-up at the fish market, and using wooden blocks and some very inauthentic aluminium wire to prop our Jenny up. Despite the beautiful summer weather it wouldn’t dry in the open air and eventually it began to decompose. Flies were also an issue.



Image: Sophia Hendrikx

Attempt # 2 was dried in my oven at a low temperature and with the door ajar. While this is a good way to dry small strips of meat or fish, it turns out it is not a suitable method to dry a large ray. It came out partially dried and partially cooked.




Image: Sophia Hendrikx

Eventually I decided to mummify my Jenny Hanivers using a combination of kitchen salt, cleaning soda, and baking soda. A similar method of mummyfication was tested by the Science Museum of Minnesota. For smaller specimens pure kitchen salt will also do the trick. I used little bags of salt to prop up the wings and open the mouth. This method proved slow but reliable. After six to eight weeks, depending on the size of the ray, the Jenny Hanivers are completely dry and ready to be varnished.

The Jenny Haniver for the exhibition Fish and Fiction was made by myself and Robbert in a lab at Leiden University. A short movie was made of the process.



© Sophia Hendrikx and Fishtories Blog, 2018. Unauthorised use and/or duplication of this material without express and written permission from this site’s author and/or owner is strictly prohibited. Excerpts and links may be used, provided that full and clear credit is given to Sophia Hendrikx and Fishtories with appropriate and specific direction to the original content.