Verified answer

Hi, that monster was a three toed SLOTH.

It was without hair because it had been in a lake for a while, and it was young.

Here is a picture of one in a jar and that looks just like the "monster" pictures: http://www.orble.com/images/animalembryo051.jpg

I just got back from a year in Central America, and heard no stories about monsters. I did kill a poisonous snake with a cleaver though, and many many scorpions.