When he returned to the camp where he and his students were staying, Leonard didn’t tell the group about his new purchase. As the students were preparing for the 400-mile trip back to Moorhead, they opened the back of the van and discovered that Leonard had sacrificed valuable luggage space for a 70-pound piece of poop.

The purchase was the largest addition to Leonard’s collection of coprolites, or petrified dung. The piece is one of many in a large “deposits” of ancient dung, which was likely made by a Sourapod, a long-necked, long-tailed dinosaur in Utah.

Although his specialty is fish paleontology, Leonard said coprolites fascinate him. He has collected about a dozen pieces, ranging from large blocky dinosaur dung to small squiggly turtle poop.

Because of the different ways coprolite is preserved, dung from the same dinosaur may appear different.

“There are all sorts of dinosaur coprolites, and they all look subtlety different,” Leonard said.

The process of the dung turning into a coprolite begins after it's buried in sediment—similar to petrified wood or fossilized bone. After a few decades, the minerals within the sediment begin to replace the substance of the dung, and the coprolite starts to acquire the qualities of the sediment.

“ Becoming a fossil, it’s incorporated part of the sediment itself,” Leonard said. “It’s becoming more rock-like. It’s becoming the process that preserves it.”

Like fossils, the condition of the coprolite depends on how well it’s preserved. Leonard said if the coprolite is immersed in dense sediment, such as mud, the fossil will retain more of it’s own minerals. However, if immersed in sand where water can freely move in and out of the specimen, it will become more rock-like.

Leonard has collected coprolites for nearly 15 years. His interest was sparked as a graduate student at the University of Utah, where he met Karen Chin, a leading authority on coprolites. Chin was researching the minerals found in coprolites when she discovered high methane in the fossils. It supported a theory that during the cretaceous period the world was in a greenhouse state, which is similar to the current age, but with methane instead of carbon dioxide. Leonard said the research fascinated him, and he discovered that “(the coprolites) had scientific validity even if they were just crap.”

There are traces of plant or animal parts within the coprolites, which give scientists a better idea about the behavior of the species.

“When you can find a coprolite, you know exactly what (the dinosaurs were) eating,” Leonard said. “So you know an aspect of their behavior you just can’t get from a skeleton.”

An average piece of coprolite costs about $10 per pound. Leonard said he finds most of his collection in rock shops and at national geology and paleontology conventions. Besides coprolites, Leonard also collects various kinds amber, rocks and other fossils.

He said his dream piece of coprolite would come from a predatory dinosaur such as a Tyrannosaurus Rex. These pieces are highly valuable and rarely found outside of museums.

“Those coprolites have such value, the best I’ll get is a photograph of them,” Leonard said.

Leonard said he uses his coprolite collection as a teaching tool. He often uses the coprolites in his college geology classes. He also does outreach work for the Cub Scouts, Boy Scouts and for children in elementary schools.

"I’ll bring bones and models. Then they’ll see the coprolite. This is something they talk about for months,” he said. It’s a great way to get children interested in paleontology.

More than anything, he said he collects coprolites because he thinks they’re interesting specimens that give clues to the Earth’s past.

“That’s the fun of it,” Leonard said. “They’re also fun to collect and they gross people out.”