Sloths at present have a limited geographic distribution restricted to the tropical rainforests of South and Central America, but during the late Pleistocene Epoch there were over forty genera of sloths living all over the Americas from Alaska to Tierra del Fuego.
Mylodon. Author’s sketch.
Whereas all extant sloths are small tree-dwelling animals not weighing more that 10 kg (22 lb.), ancient sloths included giants the size of elephants that became extinct some 10,000 years ago.
Among these large sloths, was the Mylodon, a herbivore about 3 m (10 ft.) long, 1,5 m (5 ft.) high and weighing more than one ton (2,204 lb.). Its thick reddish haired hide was embedded with tiny dermal bones or “ossicles”. These bean-sized bones acted as flexible protective armor against predators.
Mylodon bones have been found in several Patagonian sites, but the most famous is the Mylodon Cave (51°35′ S, 72°38′ W), located 25 km (15.5 mi.) north of the Chilean town of Puerto Natales (see my map here).
The cave is set close to the Last Hope Inlet, a long and winding fjord of the South Pacific Ocean. It is roughly two hundred meters long (650 ft.), thirty meters high (100 ft.) and about eighty meters wide (260 ft.). The area is surrounded by an open forest of Southern beech (Nothofagus) and there is evidence of human presence in the region dating back to 11,000 years BP.
In January 1895, Hermann Eberhard, a German sheep rancher was exploring the area with a group of men when he discovered a cave, and in it found a strange piece of hide.
It was 1,5 m long (5 ft.) and about 70 to 80 cm (31 in.) wide, it lacked limbs and head, and seemed to have been cut with a knife. Eberhard was sure, due to its coarse fur and thick hide, that it was unusual and did not belong to any known animal that lived in the region; yet from its fresh appearance it seemed that the animal had died quite recently.
Eberhard took this piece of skin and hung it on a tree by his home and when Dr. Nils Otto Gustaf Nordenskjöld (1869-1928), a Swedish geologist, geographer, and polar explorer visited the region a year later, he showed him the skin. Nordenskjöld, quickly guessed that it belonged to some extinct creature and did some digging in the cave, unearthing bones and dung which, together with more pieces of skin, were sent back to Sweden, where Dr. Einar Lönnberg would later (1899) identify it as belonging to a Mylodon.
Then Francisco Moreno visited the region in November 1897, and also took a piece of Eberhard’s skin, sending it back to the La Plata Natural Sciences Museum in Buenos Aires of which he was curator.
Fresh remains? Neomylodon, the living mylodon.
The fact that a hide and droppings had been recovered, was (and is) quite extraordinary; it was the extremely fresh appearance of these remains that led many to believe that they were recent, belonging to a living animal instead of an extinct species.
Florentino Ameghino wrote a striking paper in 1898 about the mylodon, but it was not based on the Mylodon Cave’s skin; he wrote about another skin that, according to him, had been found by his brother in Santa Cruz province, Argentina.
In this article Ameghino was the first to express the belief that the creature was still alive somewhere in Patagonia and that the fur found at the cave had belonged to some Indian who had used it as clothing.
Snippet view of Ameghino's 1898 "Neomylodon" Paper.
These fascinating statements caused an unprecedented popular uproar across the World and led to a "Mylodon Rush" and soon expeditions from several nations were crisscrossing Patagonia in search of a live Mylodon, the “mamifero misterioso” [mysterious mammal].
When during a lecture, the then leading British authority in zoology, Sir Edwin Ray Lankester announced that the Mylodon may still be alive somewhere in Patagonia, Mr. Pearson, the owner or London’s Daily Express newspaper quickly funded an expedition to hunt it down under the leadership of Hesketh Prichard.
Ameghino correctly identified the creature as a giant sloth because of the ossicles that were embedded in its tough hide and pronouncing it a new species promptly named it Milontidae Neomylodon listai (Lista’s New Mylodon) after the late Argentine explorer Ramón Lista who, according to Ameghino, had actually seen and shot at one of these beasts a few years earlier.
Lista, had been commissioned by the Argentine government to explore the unknown recesses of Patagonia during the border dispute that was then raging with Chile. He was a close friend of Moreno and was also acquainted to Ameghino.
Ameghino said that Lista had told him, his brother and others (verbally, yet he believed that he had also written about it) that once, while riding in the interior of the Patagonian territory of Santa Cruz, he had seen “and shot at a mysterious creature […] apparently bullet-proof, it disappeared into the brushwood, and all search for it proved futile”. Lista described the creature as a pangolin, without scales, and "covered with reddish grey hair”.
In Lista’s words -as quoted by Ameghino- the animal was:
a pangolin (Manis), almost the same as the Indian one, both in size and in general aspect, except that in place of scales, it showed the body to be covered with a reddish grey hair. He was sure that if it were not a pangolin, it was certainly an edentate nearly allied to it.
Ameghino, apparently based on his own brother’s (Carlos) reports, wrote that he had heard on many occasions allusions to a:
mysterious quadruped […] in the interior of the territory of Santa Cruz, living in burrows hollowed out in the soil, and usually only coming out at night. According to the reports of the Indians, it is a strange creature, with long claws and a terrifying appearance, impossible to kill because it has a body impenetrable alike to firearms and missiles.
The interesting thing is that Ameghino told this story after Lista’s death and lacking written corroboration, there was no way anyone could ratify or refute this story. No written proof has been found either.
Ameghino also said that at first he was puzzled by the description that Lista gave of his pangolin and unsuccessfully tried to identify the animal. When he finally got a piece of the skin from his brother, he had no doubts that Lista's pangolin was a variety of mylodon. Its smaller ossicles implied that it was a smaller species.
Ameghino’s mylodon paper irritated Moreno who was sure that the skin that he had found was very old and did not belong to an extant mylodon as contended by Ameghino. He also believed that Ameghino had made up the “pangolin” story.
To disprove Ameghino, he sent part of his skin to the British Museum at London where Sir Arthur Simon Woodward inspected it and after initially backing Ameghino and writing that the skin belonged to an animal “killed shortly before” being discovered, he recanted and later confirmed that the fur was of great antiquity and that it would not be necessary to search for the beast because it was extinct.
Moreno suspected that Ameghino’s brother had found nothing and that in fact Ameghino had written about the Eberhard cave hide; so he insisted that Ameghino produce the skin as evidence; he even asked the British Museum to request a piece of it for further studies.
Ameghino’s skin never appeared, so perhaps Moreno was right. Furthermore, there is an enigmatic note written by Florentino to his brother Carlos, which seems to prove Moreno right -that Florentino had written his paper based on the skin discovered by Moreno-: “Regarding the Neomylodon, at the [La Plata] museum the upheaval seems to have ended, because they have not been able to prove or find proof that my data comes from the museum’s specimen”.
In April 1899 a team led by Dr. Rudolph Hauthal, a geologist who worked for Moreno at La Plata, did some additional excavations and retrieved more bones and mylodon dung. Based on their findings, they re-named the mylodon Grypotherium domesticum because they believed that the beast had been domesticated.
They contended that the cave had been “closed artificially by coarse walls” to pen in the beasts and that they had found “a lot of dry grass […] that could only have been brought to this place by man” to feed the domesticated Grypotherium.
In other words, Dr. Hauthal and his colleagues concluded that the cave had been used by Indians as an ancient corral in which the ground sloths had been fed, bred and butchered. They wrote:
It is undoubtable that this dung comes from living animals; furthermore, the circumstance that it is found in only one place of the cave, shows that the animals had been enclosed in a kind of pen or pigsty [...] the dung proves to us that man has held these animals under domestication [...] it seems that the only animal other than the Grypotherium, that was allowed to live in [the cave] was the domestic dog.
We now know that this was all wishful thinking; the pen’s “rock walls” were just cave-ins of the cave’s ceiling. It is also likely that the animals clustered in caves for company or were dragged there by the some non-human predator. The mylodon remains from Eberhardt Cave have been dated to 10,832 +/- 400 years BP and 12,984 +/- 76 years for droppings and bone collagen respectively; coincidental with the end of the Megafauna’s Era.
Ironically, both Woodward’s and Haupthal’s work indicated that the skin belonged to a Pampean ground sloth of the Grypotherium genus, very closely related to the Mylodon but not a mylodon. Thus the name Neomylodon listai disappeared into oblivion. This pleased Moreno as it disproved Ameghino and deprived him of his moment of fame.
No giant sloths more recent than 10.500 BP have been found in Patagonia; and as the current vegetation is identical to the vegetation that they ate over twelve thousand years ago, climate change can be ruled as cause of their extinction. That is why the contemporary view is that human activity (i.e. hunting) was the cause of their demise.
Though Hauthal was convinced that there were no giant sloths alive anywhere in Patagonia, several expeditions were sent to search for them such as Illing’s (1898) at General Paz Lake and Hesketh Prichard’s (1900/1), who covered 2.900 km (1,800 mi.) along the southern Andes. Neither of them f0und any signs of mylodon.
Prichard concluded that there was no factual basis behind the fantasies of the mylodon myth; that the printed reports, when checked out on site, with the natives “were extremely nebulous”.
Woodward, who had inspected the Mylodon’s hide, correctly expressed his surprise that such a remarkable creature if still alive somewhere in Patagonia had never been seen by any of the other scientists and explorers who had been in the region.
Old mylodons never die...
Nevertheless, Ameghino would try to prove that there was something out there, perhaps not a mylodon, but it was a dangerous monster; the Iemisch, but that is another story.
 Hauthal, R., (1899). Reseña de los Hallazgos en las Cavernas de Última Esperanza. (Patagonia Austral). Revista del Museo de La Plata. v. ix: 409-420. La Plata.
 Lönnberg, E. (1899). On some remains of Neomylodon Listai Ameghino, brought home by the swedish expedition to Tierra del Fuego, 1895-1897, Stockolm.
 Ameghino, F. (1899). El Neomylodon Listai un sobreviviente actual de los megaterios de la Antigua Pampa. La Pirámide. La Plata. v. 1:51. 15.06.1899.
 Ameghino, F. (1898). An Existing Ground-Sloth in Patagonia. Natural Science. v. xiii:288 & 324-6. 11-1898.
 Holland, W., (1913). To the River Plate and back : the narrative of a scientific mission to South America… New York: Putnam's Sons. pp. 218+
 Prichard, Hesketh, (2002). En el corazon de la Patagonia, en busca del último milodon. Septiembre 1900 – Mayo 1901. Ushuaia: Zaguier & Urruty. pp. 311, 319 and 335.
 Bell, C., (2002). Did elephants hang from trees? – the giant sloths of South America. Geology Today. v. 18, N° 2, 03-04 2002.
 Smith Woodward, A., (1900). On some Remains of Gryptherium (Neomylodon) listai … Patagonia. Proc. Zool. Soc. pp 64-79.
 Ameghino, F. (2006). Reseñas de la Patagonia: andanzas, penurias y descubrimientos de dos pioneros de la Ciencia / Florentino y Carlos Ameghino. B. Aires: Continente-Pax. pp. 121-122.
 Hauthal, R., Roth, S., Lehmann-Nitsche, R. (1899). El mamifero misterioso de la Patagonia, Grypotherium domesticum. Revista del Museo de La Plata, v. ix: 409-474.
 Prichard, Hesketh. Op. Cit. pp. 321+.
 Roth, S., (1904). Nuevos Restos de Mamíferos de la Caverna Eberhardt en Ultima Esperanza. Revista del Museo de La Plata (1904). Volume 11. La Plata [Argentina] : Talleres del Museo de La Plata. pp.46 and 47.
 Burleigh, R., et. al., (1977). British Museum Natural Radiocarbon Measurements. Carbon 1977. Radiocarbon v. 19, N° 2:143-160.
Smith Woodward. A. Smith and Moreno, F. (1899). On a Portion of Mammalian Skin, named Neomylodon Listai, from a Cavern near Consuelo Cove, Patagonia. 'Proc. Zool. Soc.,' London, 1899, pp.144-156.
An article on the possible survival of giant sloths:
Oren, D., (1993). Did ground sloths survive to recent times in the Amazon Region? Goeldiana Zoologica, 19: 1-11.
Copyright 2009 by Austin Whittall ©