The photograph above shows a panoramic view of the famous Laguna Negra (Black Lagoon), now known as Laguna del Plesiosaurio (Plesiosaur Lake). In the image, the hills at the back are towards the east. Between them and the lake runs Route 40 and the Epuyen River which flows north (right to left in the image) towards Lake Puelo. The trees on those hills were burnt in a large forest fire in 1987.
Below is a map of the area, showing lakes Puelo and Epuyén, Route 40. The inset detail shows an enlarged view of the area and the tiny Plesiosaur lake is marked with a yellow arrow. The scale bar is 1000 m (3,28 ft.). On the large map, the snow capped Mount Pirque can be seen right behind the lake (on the left).
New - 06.10.2010 I have found new evidence that indicates that the lake may be another one. Close to this tiny Lagoon. It could be the lake now known as Chulta or Las Mercedes.
Adapted by Austin Whittall from .
Plesiosaurs (which in Greek means “close to a lizard”), were large aquatic reptiles that lived at the same time as the dinosaurs.
They were sea creatures that had a broad stocky body, a short tail and turtle-like flippers. Most had small heads and slender necks and measured between 3 and 20 m (10 – 66 ft.) long. As marine reptiles, plesiosaurs had a worldwide distribution and their fossilized remains have been found in northern and central Patagonia.
Though they became extinct together with the dinosaurs 65 Ma., in the early XXth century, one was allegedly seen alive in Patagonia.
This is the amazing plesiosaur story:
It all began with Martin Sheffield (ca.1863-1932), an American hunter and gold prospector. Neither an outlaw nor a bandit, he portrayed himself as a Texan Sheriff, who had migrated to Argentina around the end of the XIXth century and settled close to what is now the Andean town of El Bolsón (41°58’ S, 71°17’ W).
Click on the link to see a photograph of Martin Sheffield.
There were many Americans in the region at that time, and it seems Sheffield was acquainted with the famous bank robbers Butch Cassidy and the Sundance Kid. These rogues after running away from the US when things got to hot for them, had set up their base of operations at Cholila, close to El Bolsón, a safe haven out of the reach of the law. But not for long: soon after they robbed a bank at Rio Gallegos and Pinkerton Agency detectives quickly picked up the scent, forcing the bandits to hastily decamp.
Sheffield later moved to Epuyén, where he married a Mapuche woman, María de los Santos Pichun who bore his children. He prospected gold for many years and true to his own spirit, met his death panning for gold at the Las Minas Creek.
It was Sheffield who on January 19th, 1922 wrote a very strange letter to Buenos Aires Zoo Director, Clemente Onelli, telling him that he had sighted a strange creature.
Onelli (click to see a photograph of Onelli.) who had visited the region many times as a member of the Argentine-Chilean Border Commission, knew Sheffield; he had even mentioned him in his 1903 book as “Mr. Chefield [sic]”.
Perhaps this previous acquaintance prompted Sheffield to write to Onelli. His letter said the following:
Allow me to bring to your attention the following phenomenon that surely will awaken your vivid interest because it deals with the possible entry to your zoo of an animal until now ignored by the world. I will narrate the facts:
For some nights now, I have been noticing some tracks in the grass close to the lake where I have set up my hunting lodge; the track is similar to the foot print of a very heavy foot, the grass remains squashed and does not rise again which leads me to believe that the animal that dragged itself through there must have an enormous weight; I have been able to see, in the middle of the lake, an enormous animal with a head like a swan and enormous size and the movement in the water makes me suppose a crocodile body.
He also suggested that the animal could be hunted and detailed the necessary equipment (harpoons, boat and embalming materials).
The lake mentioned in the letter is the Laguna Negra (Black Lake), now known as Laguna del Plesiosaurio (42°09’ S, 71°24’ W). It is barely larger than a pond, roughly 200 m (656 ft.) long by 200 m wide; set at the base of the steep slopes of Mount Pirque (1.430 m – 4,690 ft.), it drains into the Epuyén River.
This river has its sources at Lake Epuyén (17,4 km2 – 6.8 sq. mi.) and flows into Lake Puelo, which in turn empties its waters through the Puelo River into the South Pacific Ocean (we have already mentioned some of the strange creatures seen in this river in our post on Puelo River monsters).
An expedition is hastily organized
Once Onelli made the letter’s contents public, it caused a stir and an expedition was promptly organized to search for and capture the beast that was named “the plesiosaur” by the media.
The news traveled around the world –this was eleven years before Nessie (of Loch Ness fame) was first mentioned- and headlines in Europe and the US would report the progress of the expedition.
I have already mentioned (Plesiosaur Tango) the effect of this extensive media coverage.
Some say that Sheffield was inspired by Sir Arthur Conan Doyle’s (the author of Sherlock Holmes) book The Lost World, which had been published serialized in Buenos Aires in 1914; maybe he had read it in his isolated cabin at Epuyén.
Doyle’s book portrayed plesiosaurs as moving their necks with “graceful, swan-like undulations” and as having a “barrel-shaped body and huge flippers behind the long serpent neck”; very similar to the creature described by Sheffield.
We know now that it would have been impossible for a plesiosaur to adopt a “swan-like” pose or even lift its head and neck above the water’s surface. Its body would not allow such a feat.
Sheffield’s comments about the foot print of a very heavy foot could not have been made by a plesiosaur either; the creature’s flippers would not have left a “foot print”; instead, like a turtle track, its trail would seem to be made up of lots of shallow dips made by its back flippers as it pushed itself along the ground, if and when it ever went ashore.
To be honest Onelli knew that plesiosaurs had become extinct with all other large reptiles and dinosaurs 65 Ma. He hoped that it was something else. He went on record saying that he believed that the creature reported by Sheffield was not a plesiosaur but a megatherium (a giant ground sloth, relative of the mylodon), reviving the Patagonian mylodon once again. He even brought up Lista and his pangolin shooting incident by stating that the lake creature was a “huge animal of the family, of which ancient remains -not fossil, mark you- were found in Patagonia In 1897, and one of which was fired upon and hit by the explorer Ramón Lista in 1890 without hurting it”.
In his “secret instructions” for the expedition, he stated that he had “let the general public believe that [Sheffield] had seen an exaggeratedly monstrous animal at the lake at Esquel”, which was another lake and not at the tiny Black Lake. He did this to throw any others who wanted to hunt it off the real track of the expedition.
He was also very clear regarding his belief that it was a mylodon and not a plesiosaur; his instructions stated that the expedition was to verify “the possible existence of an animal disappeared in prehistoric times; probably an edentate very close to, if not the same as the domestic Cryopterioum [sic], whose excrement and dry hide and bones were found” at Mylodon Cave in 1896.
He added that he believed (but with trepidation) in Sheffield’s story but that “I dismiss the squashed grass by the shore of the lagoon, because that place may have been a resting place for some huemul”.
It is strange that he did not consider the huemul, a stout, distinctly stocky deer with a thick coarse brown fur as a likely cause of the tracks seen by Sheffield. We have already mentioned the huemul in connection to (Patagonian unicorns) and pointed out its ease at swimming and fondness towards water.
Huemul were relatively abundant in the Epuyén region where, nowadays, a Provincial Reserve protects the few that remain in the mountains just behind the Black Lake, at cerro Pirque.
Onelli also believed that he had pinpointed the monster’s habitat:
For the last thirty years we have heard about it, only in those parts of our territory that were once claimed by Chile, on the oriental side of the divortiuim aquarum. The animal’s legend is found only in the valleys on the west of this easily surpassable line of continental waters’ divide before transposing the, for it, insurmountable line of the real cordilllera. These are the only regions where a great edentate, an animal of the lowlands, could be […] because these forested and crooked valleys were never visited by the natives of southern Argentina […] [The] current habitat should be the relatively low regions, not higher than 800 m [2,624 ft.] and very likely in the forests’ clearings and not in the thick woods, because the southern forest does not allow life under it.
He was convinced that it lived in the basins of rivers that drain into the Pacific Ocean, a region that was disputed between Argentina and Chile in the late XIXth century. The boundary line between both countries according to an 1881 treaty was to follow the highest crests of the Andes that defined the watershed. However in Patagonia, the Cordillera is transected by many glacial valleys causing some drainage basins on the east of the divide to flow into lakes whose Atlantic outlet is blocked by the glacier moraines; these rivers then bend and flow west into the South Pacific. This alteration of the spirit of the original treaty nearly led to a war. To settle the dispute the matter was referred to the arbitration of Queen Victoria, and an amicable settlement was reached in 1902. War was averted.
Perhaps Onelli believed that creature was confined to these areas not only due to the lower altitude of these basins which ensured a fairer climate, but also to the fact that it may have been a resident of the dense Valdivian Rainforest which offered more food and a thicker foliage to conceal it than the other Andean forests.
His remark about the habitability of the forests and their lack of large animals was also pointed out by Prichard. Patagonian forest animals are mainly small rodent mammals or nocturnal marsupials. This may be due to the lack of grasslands within the woods to sustain large herbivores and also to the fact that they are an isolated habitat, separated by more than 1.000 km (620 mi.) of arid lands from the nearest forests. There is no other similar “forest island” of this size in the world that has large sized native mammals; these need large extensions of continuous habitat to be able to survive.
Furthermore the Southern beech woods provide few edible seeds or fruits; this means that the niche filled by the northern hemisphere squirrel is empty. Patagonia’s small mammals survive in the underbrush, not the trees. For these reasons, these forests have a very high diversity of small rodents in comparison to other forests around the world, but no big mammals.
We will continue the "Plesiosaur saga" in our next posts. It is a long story.
Plesiosaurs Part 2.
Plesiosaurs Part 3.
 Camping y cabañas Pocho. Online Here.
 Google Earth.
 Onelli, C. Op. Cit. pp. 48.
 Fort, C., (1931). LO! New York: Claude Kendall. pp. 110.
For the original Spanish version of letter, see: El Plesiosaurio.
 The New York Times, (1922). Andean 'Plesiosaurus' May Be an Armadillo Or Modern Megatherium, Onelli Thinks. New York, US 16.03.1922. pp. 18.
 Rey, C., (2007). Nahuelito: El misterio Sumergido. Bariloche: Caleuche, 2007. pp. 8. More on this novel Here, despite being fiction, it includes transcriptions of Onelli's instructions to Frey.
Copyright 2009 by Austin Whittall ©