The Maricoxi were a tribe which was allegedly encountered in the Amazon by explorer Colonel Percy Fawcett. Although he described them as being "hairy as a dog," they also lived in villages and used tools. According to Fawcett, they lived to the northeast of the Maxubi tribe.
I whistled, and an enormous creature, hairy as a dog, leapt to his feet in the nearest shelter, fitted an arrow to his bow in a flash, and came up dancing from one leg to the other till he was only four yards away. Emitting grunts that sounded like 'Eugh! Eugh! Eugh!' he remained there dancing, and suddenly the whole forest around us was alive with these hideous ape-men, all grunting 'Eugh! Eugh! Eugh!' and dancing from leg to leg in the same way as they strung arrows to their bows. It looked like a very delicate situation for us, and I wondered if it was the end. I made friendly overtures in Maxubi, but they paid no attention. It was as though human speech were beyond their powers of comprehension.
The creature in front of me ceased his dance, stood for a moment perfectly still, and then drew his bowstring back till it was level with his ear, at the same time raising the barbed point of the six-foot arrow to the height of my chest. I looked straight into the pig-like eyes half hidden under the overhanging brows, and knew that he was not going to loose that arrow yet. As deliberately as he had raised it, he now lowered the bow, and commenced once more the slow dance, and the 'Eugh! Eugh! Eugh!
A second time he raised the arrow at me and drew the bow back, and again I knew he would not shoot. It was just as the Maxubis told me it would be. Again he lowered the bow and continued his dance. Then for the third time he halted and began to bring up the arrow's point. I knew he meant business this time, and drew out a Mauser pistol I had on my hip. It was a big, clumsy thing, of a caliber unsuitable to forest use, but I had brought it because by clipping the wooden holster to the pistol-butt it became a carbine, and was lighter to carry than a true rifle. It used .38 black powder shells, which made a din out of all proportion to their size. I never raised it; I just pulled the trigger and banged it off into the ground at the ape-man's feet.
The effect was instantaneous. A look of complete amazement came into the hideous face, and the little eyes opened wide. He dropped his bow and arrow and sprang away as quickly as a cat to vanish behind a tree. Then the arrows began to fly. We shot off a few rounds into the branches, hoping the noise would scare the savages into a more receptive frame of mind, but they seemed in no way disposed to accept us, and before anyone was hurt we gave it up as hopeless and retreated down the trail till the camp was out of sight. We were not followed, but the clamor in the village continued for a long time as we struck off northwards, and we fancied we still heard the 'Eugh! Eugh! Eugh!' of the enraged braves.
"Maricoxi" has also been used as a generic term to refer to hairy "wildmen" of the Amazon such as the mono grande, mapinguari, etc..
Fawcett, Brian & Fawcett, Percy (1953) Exploration Fawcett
Sanderson, Ivan T. "Hairy Primitives or Relic Submen in South America," Genus 18 (1962)
Eberhart, George M. (2002) Mysterious Creatures: A Guide to Cryptozoology ABC-CLIO, Inc. ISBN 1-57607-283-5