Digesting the Past: All About Gastroliths or "Stomach Stones"

Gastroliths are nature’s tiniest rock collection, but instead of sitting on a shelf, these stones travel inside the stomachs of animals. They’re not your average pebble picked up on a riverside stroll but a chosen tool for creatures like birds, alligators and even dinosaurs to assist in their digestion.

These natural grinders have sparked curiosity not only among fossil collectors but also within the scientific community. Research into gastroliths provides a review of their function, migration patterns and other mysteries from a time when dinosaurs roamed the Earth.

These smooth stones have a tale to tell, from being a crucial part of a dinosaur’s digestive process to offering clues about the paleo diet. Noteworthy is that gastroliths are not a casual digestive accessory but a result of an evolutionary strategy for survival.

See Gastroliths From a Sauropod

Imagine dinosaurs traversing ancient landscapes, gobbling up stones to aid their digestion. Now, gastroliths serve as a window into the past, providing insights into the lives of creatures that haven’t walked the earth for millions of years. Through a fascinating analysis by scanning-electron-microscope examination, scientists can look at the wear patterns on these stones, piecing together a chronological digestive tale etched in mineral form

Dietary Digesters: Gastroliths helped long-extinct animals break down tough plant material or prey. Today, these stones are polished trophies of prehistoric digestion.
Sediment Sleuths: Scientists can study gastroliths to understand sediment environments from bygone eras. It’s a bit like playing detective with pebbles!
Animal Insights: From offering clues about dietary habits to migration patterns, gastroliths keep on giving. They help paint a picture of what life might have looked like eons ago.

Animals Found With Gastroliths

According to UC Berkley, extinct animals that have been found with definite gastroliths in their bodies include plant-eating dinosaurs like sauropods, primitive ceratopsians, and ostrich-mimics, marine reptiles like plesiosaurs and (rarely) ichthyosaurs, and crocodilians. These animals mostly fit into two categories: plant-eaters (herbivorous dinosaurs and many birds) and animals that swim (all the rest).

Here are two more examples of fascinating discoveries about ancient animals and their stomach stones:

“Stomach Stones” in a Sea Monster

What’s the Story? Scientists found about 200 smooth stones inside the belly of a giant sea reptile called an elasmosaur. This creature lived a long time ago in what’s now Argentina. These stones, called gastroliths, were likely picked up in rivers or near the shore. The discovery suggests these giant reptiles might have swum into rivers or hung out near the coast, possibly using the stones to help digest their food or control their buoyancy in the water.

Where to Learn More: Read about this discovery in a study from 2013 by O’Gorman and friends. Check it out here.

Dinosaur with a Stomach Full of Stones

What’s the Story? In China, scientists found three dinosaurs named Gasparinisaura with lots of little stones in their stomach area. These dinosaurs were walking around about 70 million years ago. The stones were not there by accident; the dinosaurs likely ate them on purpose. This could mean they were eating plants and used the stones to grind up their food, kind of like a built-in food processor.

Where to Learn More: Check out the research by Cerda in 2008 for all the details. Read more here.

Collecting Gastroliths

These unique geological specimens can be a great addition to any collection, and there are a few key things to keep in mind when searching for them:

First and foremost, remember that gastroliths are typically found in association with vertebrate fossils, especially those of large herbivorous dinosaurs and prehistoric birds. So your best bet is to focus your search efforts in areas known for productive dinosaur fossil beds. Look for exposed rock layers, eroding hillsides, or stream beds where bones and teeth may have weathered out.

It’s important to note that in many areas, dinosaur fossil sites are protected by laws and regulations. Make sure to research the collecting rules and obtain any necessary permits before embarking on your gastrolith hunt. And of course, never remove bones, teeth, or other vertebrate fossils without the proper authorization.