Have you ever wondered why we can’t have giant pets like a massive red dog the size of a house? Dinosaurs were enormous, with some so big they could fill an entire room. For example, the American Museum of Natural History has a replica of a titanosaur that’s so large it doesn’t completely fit in its display area. This dinosaur was about 37 meters (122 feet) long, and its bones were bigger than people!
Dinosaurs lived a long time ago, and the Earth was very different back then. They first appeared around 230 million years ago. During their time, the levels of carbon dioxide (CO2) in the atmosphere were much higher than they are today, possibly 3 to 5 times more. This made the world much hotter, even in places that are cold now.
At the start of the Mesozoic Era, all the land on Earth was joined together in a supercontinent called Pangea. This meant the oceans couldn’t cool the land as much, creating a warm environment perfect for giant cold-blooded reptiles like dinosaurs. These reptiles didn’t need to use much energy to stay warm.
Scientists, called paleontologists, are still debating how much the atmosphere affected dinosaur size. Some think it might not have mattered at all. Another idea is that there was a lot of food available. With more CO2, there was more vegetation, which meant plenty of food for large plant-eating dinosaurs. Being bigger helped them digest plants better and made them harder for predators to catch.
As plant-eaters grew larger, predators also got bigger to catch them. This cycle continued until physical limits like gravity became a problem. On land, animals can’t grow as large as whales do in the ocean because water helps support their weight. Dinosaurs had lightweight, hollow bones, which helped them grow large without being too heavy. They also laid eggs, which made it easier to have large offspring quickly.
Interestingly, the hollow bones and egg-laying of dinosaurs have helped their descendants, birds, to fly today. Yes, birds are related to dinosaurs! Scientists are still trying to understand exactly why dinosaurs were so big, and they’re piecing together this ancient puzzle with many missing parts.
While we might not have giant pets today, we can still learn a lot from the past. Imagine having a pet dinosaur like a raptor, maybe with a bandana around its neck, named Clover. She would be the coolest dinosaur ever!
Imagine you are a paleontologist and create a diorama of a dinosaur habitat. Use materials like clay, paper, and natural elements to build a scene that includes dinosaurs, plants, and the environment they lived in. Think about how the high CO2 levels and warm climate would affect the landscape. Present your diorama to the class and explain how the environment supported the life of giant dinosaurs.
Choose your favorite dinosaur and design a trading card for it. Include facts about its size, diet, and how it adapted to its environment. Think about how its hollow bones and egg-laying habits helped it survive. Share your card with classmates and trade to learn about different dinosaurs and their unique features.
Participate in a debate about why dinosaurs grew so large. Split into groups, with each group representing a different scientific theory, such as the abundance of food or the warm climate. Use evidence from the article to support your arguments and try to convince your classmates of your theory’s validity.
Write a short story about having a pet dinosaur in today’s world. Describe how you would take care of it, where it would live, and how it would interact with modern animals and humans. Use your imagination to explore the challenges and fun of having a giant pet like a dinosaur.
Create a timeline that shows the evolution of dinosaurs into modern birds. Include key events and characteristics that changed over time. Research how features like hollow bones and egg-laying have persisted and helped birds survive today. Present your timeline to the class and discuss the connection between dinosaurs and birds.
Here’s a sanitized version of the transcript:
—
Hey, evolution, why aren’t giant pets a thing yet? If dinosaurs grew enough to fill a whole room, why can’t I have a big red dog the size of a house? Well, they would take up a lot of space, though.
Hey everyone, Lissette here for DNews. Part of what captures our imagination about dinosaurs is just how huge some of them were. The American Museum of Natural History has a cast of a titanosaur that’s so big it doesn’t completely fit in the dinosaur wing. The 37-meter (122-foot) long behemoth’s head has to poke out towards the elevators. It has individual bones bigger than people. The very name of the group of dinosaurs it belongs to has the word “titan” in it.
But when you start to consider the size of some of these extinct species, it can make you wonder, “Why isn’t any land animal this huge today?” Well, you’re not the only one. Paleontologists have been debating the same question, and they’ve come up with a number of different factors that could explain why some giant reptiles of the past dwarf modern land creatures.
It’s important to keep in mind that dinosaurs lived a long time ago. But what you may not realize is that before the dinosaurs were wiped out, they were living on a completely different kind of Earth than we do today. Dinosaurs actually started coming onto the scene about 230 million years ago. During their existence, CO2 levels varied significantly. Estimates suggest that there could have been 3 to 5 times as much carbon dioxide in the atmosphere as there is today. This means the world was generally much hotter, even at higher latitudes.
Additionally, at the beginning of the Mesozoic Era, all land was clumped together in Pangea, which meant the ocean didn’t have as much of a cooling effect on the supercontinent. This would make the planet a more hospitable place for giant cold-blooded reptiles that wouldn’t have to waste energy maintaining body heat.
It may comfort you to know that paleontologists aren’t all in agreement on how much the atmosphere impacted dinosaur size. It could have had no effect at all, and whether or not dinosaurs were all cold-blooded is still up for debate. Their size could have also been driven by an abundance of food. All that CO2 likely meant there was more vegetation. If there’s plentiful vegetation, then large herbivores can thrive. They’d benefit from being bigger because longer intestines would be better at breaking down plant matter and extracting its nutrients.
Also, if the herbivores grew larger, they would be harder for predators to take down. Until the predators got bigger. Then the herbivores would get bigger. Then the predators would get bigger. You see where this is going.
But there is an upper limit to size because of physical constraints like gravity. Part of the reason whales can get so huge is because the ocean supports their weight. On land, a similarly sized animal would struggle without some clever adaptations. Huge dinosaurs like sauropods had lightweight bones compared to mammals because theirs were hollow. Dinosaurs also had another advantage over mammals when it comes to size: they laid eggs. If they had to give birth to live young, it would be much harder for them to have large offspring quickly.
Interestingly, these traits of hollow bones and egg-laying have come in handy in a very different way today: they make it possible for the descendants of dinosaurs to fly. That’s right, I’m talking about birds.
The reasons for their size are still a matter of debate, and hopefully, more research will emerge. But at the moment, paleontologists are trying to piece together a hundred-million-year-old puzzle with many missing pieces.
For more on large saltwater creatures that are alive today, don’t miss new episodes of River Monsters, every Thursday at 9/8c on Animal Planet!
So, are you glad giant reptiles no longer roam the Earth, or would you want a pet raptor? Maybe tie a bandana around its neck and name her Clover. She would be the best dinosaur ever. Yes, she would.
—
This version maintains the original content while removing informal language and any potentially inappropriate or distracting elements.
Dinosaurs – Large reptiles that lived on Earth millions of years ago during the Mesozoic Era. – Scientists study fossils to learn more about how dinosaurs lived and what they ate.
Atmosphere – The layer of gases surrounding Earth, which is essential for life. – The Earth’s atmosphere protects us from harmful solar radiation and helps regulate temperature.
Carbon – A chemical element that is a fundamental building block of life and is found in all living organisms. – Plants absorb carbon dioxide from the atmosphere during photosynthesis to produce energy.
Reptiles – A class of cold-blooded, scaly-skinned vertebrates that includes snakes, lizards, and turtles. – Reptiles are ectothermic, meaning they rely on external sources to regulate their body temperature.
Vegetation – Plants and trees that grow in a particular area or environment. – The dense vegetation of the rainforest provides habitat and food for a wide variety of animals.
Predators – Animals that hunt and eat other animals for food. – In the wild, predators like lions play a crucial role in maintaining the balance of ecosystems by controlling prey populations.
Gravity – The force that attracts objects toward the center of the Earth, keeping them grounded. – Gravity is responsible for keeping the planets in orbit around the sun and for the falling of objects to the ground.
Bones – The hard, structural components that make up the skeleton of vertebrates. – Bones provide support and protection for the body’s organs and enable movement by anchoring muscles.
Eggs – Reproductive structures produced by female animals, containing nutrients to support the development of an embryo. – Many reptiles, birds, and amphibians lay eggs as part of their reproductive process.
Birds – Warm-blooded, feathered vertebrates that lay eggs and have wings, most of which are adapted for flight. – Birds are known for their ability to fly, although some species, like ostriches and penguins, have adapted to life on land or in water.
