This prehistoric dung to go under the hammer is an eye-watering 40 inches in length and is thought to be the longest in the world.
An auction house in Beverly Hills, California is expecting the lot to sell for as much as £6,000 on Saturday, July 26 with a public viewing tomorrow.
Auctioneer service I.M. Chait described the lengthy poo as boasting, "a wonderfully even, pale brown-yellow coluoring and terrifically detailed texture to the heavily botryoidal surface across the whole of its immense length."
However, the prehistoric beast responsible for the remarkable stool sample, which is presented in four sections upon a black marble base, is unknown.
“The dung was discovered at Wilkes Formation in Washington State and dates back to Oligocene/Miocene Epochs”Josh Chait, auctioneer
Auctioneer Josh Chait added: "The dung was discovered at Wilkes Formation in Washington State and dates back to Oligocene/Miocene Epochs which makes as young as 5 million years ago or as old as 40 million years ago."
The technical name for fossilised dinosaur dung is Coprolite, and is classified as a trace fossil, giving evidence about the prehistoric animal's behaviour — in this case, its diet.
Paleontologists have made breakthroughs in classifying fossils when the bones don't leave enough clues to go on.
The first discovery of coprolite was by fossil hunter Mary Anning, who found some in the stomach area of an ichthyosaur skeleton (a large marine reptile), cutting it open to find fossilised fish bones and scales inside.