Mono Rei

Aka: Ameranthropoides loysi, Dr. Francois de Loys, de Loy’s ape

Between 1917-1920, a Swiss geologist, named Dr. Francois de Loys and his men were searching for oil around the River Tarra and Rio Catatumbo at the Venezuelan Colombian border in South America. This mountainous region, the Sierra de Perijaa, was heavily forested, and that time was inhabited by the ‘dangerous’ Motilone Indians.

One day, while de Loys and his crew were resting near the Tarra River deep in the jungle, two monkeys suddenly stepped out of the woods, screaming and shaking branches. They were holding onto bushes, walked upright then broke off several branches, waving them like weapons. When the monkeys threw their own excrement at the terrified de Loys and his exhausted companions, they grabbed their guns and fired at the more aggressive-looking male, but killed the female. The male stepped aside, though wounded, but disappeared in the forest.

When finally de Loys returned home with the only remaining evidence, the picture, which he had placed into his travel-notebook, he basically forgot about his encounter with the unknown monkeys. Years later his friend, French anthropologist Georges Montandon flipped the pages of de Loys’ notebook, and discovered the photo.

Although Professor Montandon was familiar with most of the monkeys discovered to that date, he had never seen one like that in de Loys’ picture. Montandon speculated that the large monkey on the picture was a very human-like creature. It had no tail. Its size according to de Loys was 4 feet 5 inches. It had 32 teeth. It had all the features like the anthropoids and, therefore must be an anthropoid Ape. In 1929, he convinced de Loys to tell the story to the Illustrated London News and wrote several notes in newspapers.

At the meeting of The French Academy of Sciences in Paris Montadon tried to present some convincing ‘evidence’ about his major discovery of the American Ape, a so far unknown ‘American version’ of the African chimpanzee and gorilla, and the Asian orangutan. He and de Loys, had to face with numerous questions at the Academy. Naturalists and anthropologists questioned them very suspiciously. They raised many questions about the photograph: the size of the monkey sitting on the box, about her ‘missing’ tail, her set of only 32 teeth, her spider-monkey-like face, her female sex organ that resembled that of a male spider monkey. (Female spider monkeys have a long, bulbous clitoris, that people, even today often mistaken for the male sex organ). Spider monkeys have been observed walking bipedally for short distances.

When Montandon ran out of more convincing arguments in order to support his alleged hypothesis, he tried to bring up some anecdotes based on stories of Indian tribes about the guayazi, the di-di, and the vasitri or ‘big-devil’ that believed to attack women. A. de Humboldt, who did not believe any of these stories, attributed these alleged attacks to the spectacled bear (Tremarctos ornatus) and Marquis de Wavrin mentions these creatures as ‘marimunda’ which were later also identified as spider monkeys: Ateles belzebuth.

Montandon was defeated in scientific circles which treated his hypothesis as a fraud, but the story created some ambiguity, which led into more investigations for years to come and the question mark that a man-ape like might be still roaming the wilderness of South America jungles.


  • Heuvelmans, B. (1959). ON THE TRACK OF UNKNOWN ANIMALS (Transl. from French by Richard Garnett) Hill and Wang, New York
  • Hill, W. C. O., (1962). PRIMATES Comparative Anatomy and Taxonomy Vol. 5 Cebidae, Part B. Edinburgh University Press
  • Joleaud, L. (1929) Remarques sur l’Evolution des Primates Sud-Americains, a propos du Grand Singe du Venezuela’ Rev. sci., Paris, pp. 269-273, 11 May 1929
  • Keith, Sir A. (1929) The Alleged Discovery of an Anthropoid Ape in South America’ Man (London) 29: 135-136. Loys, F. de (1929) ‘A Gap filled in the Pedigree of Man?’ Illustrated London News, London, 15 June 1929, p. 1040
  • Montandon, G. (1929a) Decouverte d’un Singe d’Apparence Anthropoide en Amerique du Sud J. Soc. Americanistes Paris, n.s. 21
  • Montandon, G. (1929b) Singe d’Apparence Anthropoide en Amerique du Sud C. R. Acad. Sci. Paris, 11 March 1929