How To Identify Coprolite (Dinosaur Poop Fossils!)

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Coprolites are the fossilized feces of prehistoric animals (enter poop joke here!)  They can be found in sedimentary deposits throughout the world, including locations all over the United States, Canada, Australia and Europe. 

The first coprolites were discovered by Mary Anning in the early 1800’s who theorized that the strange “poop shaped” fossils she found were actually the fossilized poop of dinosaurs…the ichthyosaurs and plesiosaurus. 

Then later in 1829, William Buckland observed that the fossils she had been finding contained things such as fish scales, bones and other inclusions. And he agreed, that in fact these were dinosaur poop fossils.

Since then many other types of fossils have been found inside coprolites including plants, pollen grains, insect remains and even microscopic animal burrows!

How To Identify Coprolites

In this guide on how to identify coprolites, you’ll learn about all the different types of samples and what kinds of things to look for when looking for your own coprolite specimen.

Shape

Does the rock look like poop? Identifying coprolites can be tricky, but one of the easiest and fastest ways to identify a coprolite is by their shape. If you’re unsure if a rock is a coprolite, try comparing it to the size and shapes of modern poop balls.

Does it have a flat pancake appearance like a modern day cow? Or is it sausage shaped like a dog poop?

The overall shape is going to be the first clue on whether or not you have coprolite.

Location

This may seem obvious, but the next thing to consider in deciding whether or not you have actual coprolite is where it was found. 

Have other fossils like bones, teeth or even animal tracks been found in the same area? Coprolite is almost always accompanied by other fossilized evidence of prehistoric animal activity. Rarely, if ever, will coprolite be found completely on its own.

Inclusions

Some coprolites have some crazy stuff found inside of them such as fish scales, plant material, bones and teeth! It’s neat that we can see these things inside an animal’s poop that lived millions of years ago. 

Just like modern day animals, some prehistoric animals ingested stones for ballast or digestive purposes. These are known as gastroliths which can also be found in coprolites. If present, they generally have a smooth surface.

Looking Under A Microscope

The way an object looks under a microscope can tell you whether or not it’s a coprolite. If your specimen appears to be granular, unfortunately, it is probably not a coprolite. 

There are exceptions to this rule though. For example, marine creatures that eat sediment from the bottom of the ocean floor would have food particles in their droppings and appear granular even if they were actually coprolites. 

That is why understanding where your specimen was discovered and what kind of geology resides there is so important!

Composition

Because herbivore feces tends to break a part and decompose rapidly, it rarely survives the fossilization process. So most fossil poo that is found is from carnivores. 

The reason for this is that their poop is usually high in calcium phosphate, the same mineral found in bone. This mineral can appear in many forms. It can be hard and dense or soft and porous. 

If the potential coprolite appears soft and porous, there is a quick test that is often used in the field. If you wet your finger and touch the stone to the tip of your wet finger and it sticks, chances are, it is high in calcium phosphate and could possibly be a coprolite.

If the calcium phosphate takes a harder, more dense form, the “wet finger test” won’t work. In some instances, chemical analysis is required to definitively identify the mineral composition.

What Are Coprolites?

Coprolites are the fossilised faeces of animals that lived millions of years ago. Coprolites are trace fossils which means that they are not fossils of the animal’s actual body, but of something that came from the animals body. 

Coprolites are like time capsules and provide an unparalleled insight into the past. That’s because many coprolites contain inclusions, or tiny fossilized fragments of the food or material that the animal ate. 

Do Coprolites Smell?

No, coprolites do not smell. Even though a coprolite is the fossilized remains of an animal’s actual poop, it’s no longer poop.  Since it’s gone through a fossilization process and all of the biological material has been replaced by minerals and turned into stone, there’s no longer a poopy odor to the animal dung. 

How Are Coprolites Formed?

How does poop become a fossil? When the conditions are just right, it happens just like any other fossilization process. The process is very similar to how petrified wood is made.

In order for the poop to turn into a fossil, it had to be covered up very quickly with soil rich in minerals. Once covered, and the poop is deprived of oxygen, the decomposition process of the organic material is halted. 

Over many, many years the original organic poopy material is infused with mineral rich water. Much like petrified wood, these dissolved minerals begin to crystalize over time, replacing the original organic material with crystalized minerals, essentially turning the poop into stone.

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