The Whipping Molesque, AKA the "Rocky Mountain Oyster," is a three-foot-tall mollusk native to the American Rocky Mountains.
The Molesque moves around using a large sucker-foot. Its shell is conical, bifurcated, and variegated with vertical blue/green ridges. When the creature is threatened, it slams shut like a bear trap, producing an echoing "snap."
The Molesque lives at the bottom of lakes, but comes onto land to hunt -- ironically for river fish. The creature sits waiting by the side of a river like a fisherman. When it senses a fish nearby, it shoots a long poison-tipped appendage into the water. The whip-like appendage paralyzes and grabs hold of the fish, retracts into the Molesque's shell, and the predator begins to digest its meal.
Like an oyster, the Molesque produces a pearl when something irritates its soft flesh. The pearls, which can be as much as a foot in diameter, would surely be worth millions if put to auction... However, if the exact location of these animals were ever revealed, it is almost equally certain that the gold rush of poachers would soon bring about their extinction.
In the name of science, and at great personal risk, I have procured and sawed open several pearls. It appears that the majority have been formed around birds, which presumably tried to eat the Molesque's flesh. One contained a human hand, severed at the wrist.
Although as yet unproven, it is my belief that Molesques go to water-filled underground cave systems to reproduce -- and that they also return there to die.