Older reports and sightings
Perhaps the first formal record of such creatures called Marimondas or Maribundas comes from 1533, when Pedro Cieza de León reported sightings from natives and from one Spanish settler. In his writings, Sir Walter Raleigh made brief note of reports of large monkey-like creatures in South America. He did not see such a creature himself, but deemed them credible, noting the ubiquity and consistency of reports.
The German naturalist Alexander von Humboldt, who travelled in South America during early 19th century, heard stories from Orinoco about furry human-like creatures called Salvaje ("Wild"), which according to Humboldt were rumoured to capture women, build huts and to occasionally eat human flesh. Both the superstitious natives and the missionaries in the area believed in these stories, but Humboldt recognized similar myths from the Old World, and concluded that the stories had entered into South America from the Europeans. The cryptozoologically interested naturalist Philip Gosse also tried to examine these legends during his travels in Venezuela during the mid 19th century, but with no real success (Sjögren, 1980).
Modern reports and sightings
The so-called Loys' Ape was photographed in 1920; critics of the photograph allege that it was simply a spider monkey, while others believe it could be an unknown creature. In 1931, inspired by Loys' ape, three Italians made an expedition to the Mazaruni River in Guyana, but without further evidence than more alleged sightings from the residents. Bengt Sjögren writes (1980) that: "They returned home with a couple of eyewitness-reports, that give the impression that the interviewed tried to make fun of the [sic?] them."
An American millionaire also set up a reward of 50,000 dollars to the one who could find a specimen, but nobody seems to have claimed the reward. The American scientist Philip Herschkowitz, who traveled in the same areas as de Loys, concluded that the story was a myth whose origin was the spider monkey, Ateles belzebuth. However, in 1951, a Frenchman named Roger Courteville claimed to have seen an apeman at the same river where de Loys said he had seen his creatures. Like de Loys, he presented a photograph of the creature as evidence. According to Sjögren (1980) the photo was a hoax, a manipulated version of de Loys photograph.
The cryptozoologists Bernard Heuvelmans and Charles Dewisme planned to travel to Sierra de Perijaá in Colombia to find or document the mysterious ape, since there are similar rumours that Humboldt encountered from that area. There have been reports from more recent decades: In 1968, explorer Pino Turolla saw Loys' photograph, and set out to investigate. Turolla claimed two brief sightings of similar creatures: spotting two large bipeds in the area near where Loys asserted he’d encountered and photographed the creature, and a second brief sighting in eastern Ecuador.
In 1987, Gary Samuels (a mycologist studying under a grant from the New York Botanical Garden) was studying fungi in Guyana. Hearing footsteps nearby, he glanced up, expecting to see his Guyanese assistant. Instead, he saw a bipedal, ape-like creature standing about five feet tall. Samuels said the creature bellowed at him, then ran away.
As mentioned above, Humboldt considered the reports of Salvaje to be just myths that came to South America with European colonists. The Swedish author Rolf Blomberg speculates (1966) that rumours of hidden monsters in the Amazon basin might have been inspired by Arthur Conan Doyle's book The Lost World (1912) combined with exaggerated reports of sightings of unusually large spider monkeys (Sjögren, 1980), and Bengt Sjögren (1962) remarked: "For critically educated zoologists is of course all this 'ape mystery' just a good joke."
Another problem with potential hominid cryptids in South America is that of the distinct biogeographical distribution of primate species. Hominids (Hominoidea) are restricted to the Old World (except humans, of course), while the New World is populated by smaller, often arboreal monkeys with long tails and flatter noses (Platyrrhini). Consequently, there is little evolutionary and biogeographical reason to expect a hominid primate hiding in the jungles of South America (Sjögren, 1980).