In this activity we are going to take a look at how some dinosaurs may have digested their food.
A dinosaur that chewed with gastroliths. Credit: Wikimedia Commons/A. Atuchin CC BY 4.0
You will need
- A plastic bottle, preferably with a fairly large opening at the top
- Water
- A lettuce leaf
- Some gravel or other rocks – try to get rocks that are fairly large, but will still fit into the bottle
- A strainer or colander
Safety
When going outside to collect rocks, be sun safe and let an adult know where you’re going.
What to do
Fill the bottle about 1/3 of the way with stones.
Pour in water until it is about level with the top of the stones.
Put the lettuce leaf into the bottle. You may need to roll the leaf into a tube to get it in the bottle.
Screw the top on firmly and shake the bottle for about 60 seconds. Make sure you have plenty of space around you before you start shaking.
Hold a strainer or colander over the sink and pour the contents of the bottle into the strainer or colander. Remove the rocks and take a look at the lettuce leaf.
Rinse and recycle the bottle once you’re done. Return the rocks to where you found them.
What’s happening?
Gastroliths from the Jurassic Period. Credit: Wikimedia Commons/Wilson44691 CC BY-SA 3.0
You should find that the lettuce leaf has been crushed, as though it had been chewed up. The stones that did this are called gastroliths.
We chew food to help get the nutrients out. This is especially important when eating vegetables and other parts of plants. But chewing is a problem for plant-eating birds.
Birds have beaks instead of teeth, so they can’t chew the way we do. Instead, they swallow some stones and hold these stones and the food in a special part of their stomach called a gizzard. As the birds move around these gastroliths grind the food, as though it was being chewed up.
Birds aren’t the only creatures to have used this trick. Some plant-eating dinosaurs had beaks instead of teeth and some had teeth that weren’t designed for chewing. And paleontologists have found small rocks inside some dinosaur skeletons. With all that evidence, scientists are pretty sure that some dinosaurs used gastroliths to help them digest their food.
Paleontologists can use several ways to tell if a rock was a gastrolith. If a rock is found near fossil bones and it’s lying where the stomach or gizzard would have been, then it’s probably a gastrolith. Another clue is that gastroliths are smooth thanks to all the rubbing they do against other stones in the gizzard. If you kept shaking your bottle, the rocks inside would eventually get rounded edges and smooth surfaces, too.
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