The word “dinosaur” is derived from the Greek words deinos meaning “terrible” and sauros meaning “lizard”. It means terrible lizard, or fearfully great beast. This term has been applied to any large prehistoric animal that lived during the Mesozoic Era. However, not all of these animals are actually dinosaurs. Many of them are just closely related to dinosaurs and often get mistakenly categorized as such.
Some of the most popular prehistoric animals that get mistaken for dinosaurs are pterosaurs, plesiosaurs, ichthyosaurs, and mosasaurs – many of which feature in this article. You might also be surprised to learn that it’s actually quite common for the classification of certain fossils to change over time, as our understanding of these fascinating prehistoric creatures improves with time – something which can further add to confusion people have between dinosaurs and non-dinosaurs that lived around the same time.
In this article, we’ll take a closer look at some of the prehistoric animals that are commonly mistaken for dinosaurs by the general public, providing an overview of these creatures, what they ate, when they went extinct, and when they were first discovered. So, without further ado, let’s begin!
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Did other animals that live at the same time as the dinosaurs?
Yes, there were many other animals that lived at the same time as the dinosaurs. In fact, many of these animals are still alive today! Some of the most well-known animals that lived during the Mesozoic Era include mammals, turtles, crocodiles, lizards, and snakes.
The dinosaurs were dominant predators during the Mesozoic Era, but they were not the only predators around. There were also many other animals that could hunt and kill dinosaurs, including large reptiles such as crocodiles and snakes, as well as birds of prey.
How common is it for dinosaur fossils to be reclassified as not being dinosaurs?
It’s more common than you think! Dinosaur fossils are often reclassified as not being dinosaurs. In a study of nearly 1,500 species of fossil animals, almost one-third were found to have been misclassified.
This was most often due to the fact that they were similar in appearance to dinosaurs, but did not share all of the same characteristics. This highlights how difficult it can be to determine what an animal is, based on its fossilized remains.
Despite this, there are still many animals that we classify as dinosaurs. This is because they share a number of key characteristics with true dinosaurs, such as a lack of fur or feathers, and certain types of bones.
So, while you might not be able to tell a dinosaur from its fossil remains, there are still some ways to tell if an animal is closely related to one.
1. Pterodactyl

Pterodactyls are often mistaken for dinosaurs, but they are actually a separate group of animals. They share some similarities with dinosaurs, but pterodactyls are their own unique creatures.
They are the oldest known flying vertebrates, and can be traced back to the Late Jurassic period. Pterodactyls come in a variety of shapes and sizes, and some even had crests on their heads.
Pterodactyls were carnivores, and ate a variety of prey, including fish, small mammals, and even other pterodactyls! They had sharp teeth and claws that helped them take down their prey. Amazing flyers, and could reach speeds of up to 60 miles per hour! Pterodactyls are definitely not dinosaurs, but they are still fascinating creatures that are worth learning about.
Pterodactyls were first discovered in the early 1800s by a German naturalist named Georg August Goldfuss. He found some fossils in Bavaria, and initially thought they were birds. It wasn’t until later that someone realized these creatures were actually flying reptiles.
Pterodactyls went extinct around the same time as the dinosaurs, at the end of the Cretaceous period.
2. Mosasaur

Mosasaurs were a diverse group of marine reptiles that lived during the Late Cretaceous Period. They were closely related to monitor lizards and snakes, and are often mistakenly categorized as dinosaurs.
Mosasaurs were predatory animals that ate fish, sharks, and other marine reptiles. They ranged in size from small species that were less than a meter long, to the largest known mosasaur, Hainosaurus, which reached lengths of up to 18 meters.
Although mosasaurs are often thought of as dinosaurs, they actually belong to a different group of reptiles called the saurians, which include crocodiles, lizards, and snakes. Mosasaurs are more closely related to these animals than they are to true dinosaurs.
There are many differences between mosasaurs and dinosaurs. For example, mosasaurs had four flippers, while dinosaurs had two legs. Mosasaurs also had tails that helped them swim through the water, while dinosaurs had tails that were used for balance.
Despite these differences, mosasaurs are often mistakenly referred to as dinosaurs. This is likely because they were some of the largest and most fearsome predators of their time. Mosasaurs became extinct by the end of the Cretaceous Period.
Mosasaurs were first discovered in the early 1800s, when a fossilized skull was found in a quarry in Maastricht, Netherlands. This quarry was famous for its fossils, and many different types of mosasaurs have been found there.
3. Plesiosaurs

Plesiosaurs are a group of marine reptiles that were once thought to be dinosaurs. They are now known to be a separate group of animals that are closely related to dinosaurs, but are not actually dinosaurs themselves.
Plesiosaurs lived during the Jurassic and Cretaceous periods, and were some of the largest marine reptiles that have ever lived. They are easily distinguished from true dinosaurs by their long necks, small heads, and large flippers. While they may look like dinosaurs, they are not actually classified as such.
Plesiosaurs were predatory animals that ate fish, sharks, and other marine reptiles. They ranged in size from small species that were less than a meter long, to the largest known plesiosaur, which reached lengths of up to 18 meters.
Plesiosaurs were first discovered in the early 1800s by Mary Anning, a British fossil hunter. Since then, many more Plesiosaur fossils have been found all over the world. Although they are not technically dinosaurs, they are still fascinating creatures that are worth learning about.
The Plesiosaurs became extinct at the end of the Cretaceous Period. Although they are no longer around, they have left behind a rich fossil record that has allowed us to learn about these fascinating creatures.
4. Dimetrodon

Dimetrodon is a genus of synapsid that lived during the Permian period. It is often mistaken for a dinosaur, but it is actually more closely related to mammals.
Dimetrodon was a large, predatory creature that had a sail on its back. Dimetrodon was a carnivore, and it probably ate small animals such as reptiles and amphibians. It is one of the earliest known mammals, and it played an important role in the evolution of mammals.
Dimetrodon was first discovered in 1878 and named by Edward Drinker Cope. It was originally classified as a dinosaur, but it was later reassigned to the new order of synapsids. Synapsids are a group of animals that includes mammals and their ancestors.
Dimetrodon became extinct around the end of the Permian period, which was around 245 million years ago.
5. Pteranodon

Pteranodon was not a dinosaur, but was instead a prehistoric reptile that lived during the late Cretaceous period. It is related to the dinosaurs, but is not actually one of them.
Pteranodon is best known for its large wingspan, which could reach up to 25 feet in length. It is believed that Pteranodon used its wings to glide or fly through the air, although it is not known for sure how it did this.
The first Pteranodon fossils were discovered in the late 1800s, and since then, many more have been found. Today, Pteranodon is one of the best-known prehistoric reptiles and is one of the most popular dinosaurs in popular culture.
Pteranodon is believed to have eaten a variety of things, including fish, insects, and other small animals. It is likely that it was also cannibalistic, and ate the smaller members of its own species.
Pteranodon became extinct around the end of the Cretaceous period.
6. Ichthyosaurs

Ichthyosaurs were a large group of marine reptiles that lived during the Triassic, Jurassic, and Cretaceous periods. They were often mistaken for dinosaurs, but they are actually not related to them at all.
Ichthyosaurs were more closely related to lizards and snakes than they were to dinosaurs. Despite this, they are still often classified as dinosaurs due to their similar appearance.
Ichthyosaurs were predators that ate fish, sharks, and other marine reptiles. They ranged in size from small species that were less than a meter long, to the largest known ichthyosaur, Shonisaurus, which reached lengths of up to 21 meters. Ichthyosaurs went extinct at the end of the Cretaceous Period.
The prehistoric marine reptile was first discovered by a young boy named Joseph Anning, who in 1811 found ichthyosaur fossils. The rest of the creatures skeleton would be found by his sister Mary, who later went on to become a respected paleontologist and fossil collector.
7. Quetzalcoatlus

Quetzalcoatlus is a pterosaur, a flying reptile that lived during the Late Cretaceous period. It was one of the largest pterosaurs of all time, with a wingspan of over 36 feet!
But despite its size, Quetzalcoatlus was actually closely related to smaller pterosaurs like Pteranodon. So while it might look like a dinosaur, Quetzalcoatlus is technically not one.
Quetzalcoatlus probably ate a variety of things, including fish, insects, and small mammals. It was a large predator, so it probably hunted and ate animals that were its own size or larger.
First discovered in Texas in 1971 by Douglas A. Lawson, in the Maastrichtian Javelina Formation within the Big Bend National Park. Since then, only a handful more have been found, all of these discoveries having been made in Texas.
Quetzalcoatlus became extinct around the end of the Cretaceous period.
8. Scutosaurus

Scutosaurus is a genus of herbivorous ankylosaurid dinosaur that lived in what is now Russia during the Late Cretaceous period, around 100 million years ago.
Despite its name, Scutosaurus was not a true dinosaur; rather, it was a close relative of dinosaurs. Nevertheless, it is often mistakenly categorized as a dinosaur due to its similarities in appearance and habits.
Scutosaurus was a herbivorous ankylosaurid dinosaur that ate plants and other vegetation. It had a strong jaw and sharp teeth that were perfect for grinding down tough plants.
The first remains of this creature were found by Vladimir Prokhorovich, a Russian paleontologist, in the Norther Divna River, Siberia, way back in 1899. These remains were recovered in 1914 and the specimen was officially identified and named by British zoologist David Meredith Seares Watson in 1917.
The latest known fossils of Scutosaurus are from the Campanian–Maastrichtian stage of the Late Cretaceous period, meaning that it became extinct around 70-80 million years ago.
9. Kaprosuchus

Kaprosuchus was a crocodile-like animal that lived during the Cretaceous period. It is often mistaken for a dinosaur, but it is actually not a dinosaur. It is closely related to them, however, and shares many of their characteristics.
Kaprosuchus was a large animal, reaching lengths of up to 9 meters (30 feet). It had a long snout and sharp teeth that were perfect for catching its prey. This animal was definitely a predator, and it would have been a fearsome opponent for any other creature that crossed its path.
Kaprosuchus was a carnivorous animal, and its diet would have consisted mainly of small animals like lizards, mammals, and birds. It may also have eaten fish and other aquatic prey. Kaprosuchus was definitely a predator, and it would have been a fearsome opponent for any other creature that crossed its path.
The prehistoric creature was discovered by Paul Sereno in 2009, on an expedition to Niger – a country in Africa. So far only a skull has been recovered, which is currently the entire basis for our understanding of Kaprosuchus. The skull itself – which being somewhat crocodile like – has a range of unique features from which we’re able to determine a fair bit about what this animal would have been like.
Kaprosuchus is thought to have became extinct around the same time as the dinosaurs, at the end of the Cretaceous period.
Final thoughts
Dinosaurs are some of the most well-known prehistoric creatures, but they’re not the only ones! There were many other animals that lived during their time and some of them are still being discovered today. In fact, new fossil discoveries are happening all the time and scientists are learning more about these amazing creatures every day.
Some of the animals that are commonly mistaken for dinosaurs are actually just closely related to them. This is because scientists are still learning about these animals and classifying them in different ways. As our understanding of the awe-inspiring, prehistoric creatures continues to improve, we’ll likely see other dinosaurs reclassified overtime, just like some of those included in this article have been.
We hope you’ve enjoyed learning about some of the non-dinosaur prehistoric creatures that are often mistaken for them. Stay tuned for more fun facts and information about all things related to dinosaurs!
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