Plant-Eating Dinosaurs: Lessons in Dietary Habits and Adaptations ,Some dinosaurs ate smaller lizards, eggs, or even early mammals. Others hunted other dinosaurs as prey, or dig up the remains of dead animals. However, most dinosaurs ate plants.
Research shows more than 180 dinosaurs preferred a plant-based dietbut it’s quite difficult to put an exact number, says Paul Barrett, a palaeontology researcher at the Natural History Museum in London.
“There’s a bit of a gray area because some of the dinosaurs that we think were mainly plant-eating may actually have been omnivores,” adds Barrett.
Most plant-eating dinosaurs fell into two categories: There were ornithischian—meaning “bird-thighed”—dinosaurs, such as Triceratops, Stegosaurus, Iguanodons and ankylosaurs and sauropodomorph dinosaurs, which include long-necked dinosaurs such as Diplodocusbrachiosaurus and brontosaurus.
Several theropod dinosaurs—like the horse Chilesaurus — seems to have gave up meat for the plant dietbut this evolutionary development does not happen so often.
“The interesting thing about herbivory is that we think it has at least three (and probably many more) independent origins since the dinosaurs,” says Barrett. “We think the first dinosaurs were either carnivores or mixed eaters, so the ability to eat a purely vegetarian diet is something that arose independently in each of these groups at multiple times.”
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Which dinosaurs preferred a plant-based diet?
Researchers have known that many dinosaurs had a penchant for plants for quite some time. “Historically, the understanding that many dinosaurs ate plants is older than the term dinosaur itself,” says David Buttona dinosaur researcher at the University of Bristol.
Historical image of a herd of Igaunodons by German artist Heinrich Harder. Early reconstructions of the dinosaur show it standing upright in a kangaroo-like stance, although more recent studies show it walked on all fours. (Credit: The Wonderful Paleo Art of Heinrich Harder/Public Domain)
After its opening in 1822 Iguanadonone of the first dinosaurs to be formally described, is named after its teeth, shaped like those of living iguanas. Since iguanas are herbivores, this first discovery lit the way for interpreting other dinosaurs as herbivores.
“Are their teeth essentially like those of living herbivorous reptiles, primarily iguanas?” Button says.
Dinosaurs’ teeth reveal what they ate
Even today, tooth shape is still one of the main indicators of a dino’s food preferences. Carnivorous dinosaurs had pointed teeth for piercing skin, for example, as well as perpendicular serrations like a steak knife for cutting meat fibers.
Herbivorous dinosaurs, meanwhile, had different forms of teeth for shredding plant fibers: The animals tended to have scythes, large serrations to hold plants in place and help them cut them, and flat surfaces for grinding—like horse teeth – and a large number of teeth for pulping and chewing plants. Since plant material is much more difficult to digest than meat, it was crucial for herbivores to have different mechanisms to efficiently break down their food.
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Now, thanks to emerging technologies, scientists are identifying more specific details about dino diets than before. from looking at the microscopic wear on the teethaccording to Barrett, scientists can determine what types of plants the dinosaurs ate.
They can also infer the height at which these animals were feeding by looking at scratches on their teeth – which can show the amount of grit the dinosaur ingested along with the plants, revealing whether they were eating closer to ground level or towards tree tops, for example.
“But it’s actually very difficult to get into the specifics of what types of plants certain dinosaurs ate,” says Barrett.
A peek inside a dinosaur’s stomach
There are other methods of studying dinosaur diets. We can infer all kinds of feeding behavior from preserved gut contents. Already at the end of the 18th and the beginning of the 19th century, well preserved, mummified remains of a duck-billed hadrosaur dinosaur were discovered in Canada — and researchers found pine needles and other plant material in the corpse’s intestines.
These specific findings were later overturned, as the vegetation found in the dinosaur’s stomach turned out to be debris washed into the body cavity after death. But these initial observations did show that scientists could examine the preserved gut contents of dinosaur remains to gauge what they ate.
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Illustration of Borealopelta nibbling on ferns. (Credit: Julius Csotonyi/Royal Tyrrell Museum of Paleontology)
In 2020 for example intestinal contents extracted from an armored dinosaur Borealpeltar they had charcoal in them, indicating the animal had ventured into burned areas to chew on re-emerging vegetation after wildfires, Button said.
The characteristics of plant-eating dinosaurs
In addition to teeth, the presence of a beak usually indicates that the dinosaur had a herbivorous diet. But besides that, Button’s research specializes in the study of dinosaur jaw muscle mechanics to find out whether they prefer meat or plants, and the differences in how they eat different types of plant material.
“What you see in carnivores is less efficient [jaw closure], but just more overall muscle strength,” says Button. “Whereas with a lot of herbivores, depending on what they’re doing, closure is effective, speed is no longer important and things like that.”
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What’s more, there were some herbivorous dinosaurs that, like birds, used a grizzly—a muscular second stomach for digesting food—along with stomach stones to crunch vegetation instead of chewing it in their mouths.
“Finding a group of these little pebbles together in the middle of a dinosaur’s ribcage is pretty good evidence that it might have had one of these millstones, but we only find them in a handful of dinosaurs,” Barrett says.
The case for giant entrails
On the other hand, not all herbivorous dinosaurs liked to chew their food. These herbivores don’t need chewing teeth or very efficient closing jaws—they prefer to swallow their vegetables in larger portions and then digest them in their intestines. This is an alternative strategy that we see in some living animals, such as turtles, to some extent.
That’s why scientists can also look at the size of a dinosaur’s gut to find out if it ate plants or not.
Sauropod dinosaursfor example, they evolved to have a long neck with a small, light skull at the end, so they couldn’t then develop a battery of chewing teeth that would have been too heavy for their long necks.
(Credit: David Roland/Shutterstock)
As a result, some scientists speculate that they are needed super big stomachs to ingest whole high-energy foods. Larger guts are also better suited to larger animals, which is one reason why so many herbivorous dinosaurs were also the largest overall.
Different ways of eating plants make it easier to live together
Clearly, not all dinosaurs were created equal. And not only do the various characteristics of herbivorous dinosaurs differ from what scientists see in carnivorous dinosaurs, Button says, but they also remind us of the breadth of different ways to exist as plant-eating dinosaurs. This in turn helps us learn a little more about how these giant creatures can coexist.
This diversity also helps maintain more diverse communities, similar to what we see in modern ecosystems where herbivores (even if their diets overlap) specialize in feeding in different ways, on different parts of the same plants or entirely with different plants.
“This removes the mechanisms that maintain diverse communities over evolutionary time,” says Button. “It also shows that some of the same ecological forces shaped animal communities in the Mesozoic as they do today.”
Herbivores and the ecosystem
Whether we are talking about herbivores today or in the age of dinosaurs, most animals tend to eat plants. So if we don’t understand what plants are doing, Barrett says, we’re missing a big part of that equation.
“If you want to understand how any ecosystem works, you really need to know what the herbivores are doing,” says Barrett.
But paradoxically, eating plants is also the harder path from an evolutionary perspective. Although it’s hard to catch animals to eat, that’s the hardest part of being a carnivore.
Once you’ve caught your prey, that meal is probably high in nutrients and you don’t need to eat as much. Plants, on the other hand, are very abundant, but you have to eat a lot more of them. Besides, plants are too chemically and physically more difficult to digest.
“It’s actually the evolutionarily harder thing to do,” says Barrett. “So understanding why the animals had to do this so many times is actually an interesting question.”
Herbivorous dinosaurs teach us about evolution
Dinosaurs can provide researchers with a fascinating insight into the inner workings of evolution for several reasons: they are fairly well understood; they have lived so long; and inhabited drastically different environments.
“I’m not necessarily going to pretend that the results we get from dinosaurs are directly related to understanding how things are going to change in the future,” Button says. “But they still help to derive evolutionary models, or even ideal evolutionary rules, that will help us understand how ecosystems respond to future changes.”
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