The Predator, or simply swamp monster, is large and dark green, with two long, clawed forelimbs, and with a very large crocodilian head. The creature's mouth is large enough to swallow dinosaurs whole and brims with sharp teeth, and two long horns jut from the skull like those of a bull.
The Predator inhabits swamps and is an indiscriminate eater, swallowing whatever creatures it can. It takes a few days to digest its food, giving those swallowed time to reflect upon their situation.
The creature gets its name, at least outside the series, from its appearance as the title character in the show-within-a-show Totally Hidden Predator. It is not known to have any other official name.
The swamp monster is a hand puppet, matted into the scene to look like a giant creature. Every swamp monster seen on Dinosaurs looks identical, and given the fact that many of the puppets on Dinosaurs were regularly reused as different characters, and only one swamp monster at a time is seen, it is unclear whether all swamp monsters look the same, or if all appearances by a swamp monster are actually appearances by the same swamp monster.
This puppet originally appeared in The Jim Henson Hour episode 'Monster Maker'.
A photo caption in Matt Bacon's book about Jim Henson's Creature Shop, No Strings Attached, describes this puppet as a demon.