The 9 Closest Living Things to Dinosaurs (Not Only Birds)


Spinosaurus-eating-AdventureDinosaurs

Although scientists consider birds to be the only dinosaur descendants still in existence, there are many other living animals that scientists believe are closer to dinosaurs. The closest living things to dinosaurs need to be taken a look at in terms of classification of species.

Dinosaurs are classified as reptiles, a group that includes crocodiles, lizards, turtles, and snakes. Of this large group of animals, other than birds, crocodiles are the closest living things to dinosaurs. 

The Key Differences and Similarities from the Closest Living Things to Dinosaurs

Before we get into the list of animals closely related to dinosaurs, let’s back up a little and cover some differences and similarities. Below are some similarities between dinosaurs and modern-day living organisms.

● Dinosaurs built nests and laid eggs just like modern birds and reptiles. Moreover, dinosaurs, reptiles, and birds are all vertebrate animals, which means that they all have a spine with some appendages. 

● Both reptiles and dinosaurs have dermal bone structures, such as the plates on the skin, the presence of an endoskeleton, and scales. 

● Reproduction: The vast majority of birds and reptiles are oviparous. It’s the term used by scientists to describe living organisms that hatch from eggs. 

There are only a few living reptilian species that are ovoviviparous, a scientific term used to describe the process of young ones hatching from eggs that have been incubated inside the animal’s body. 

Dinosaurs were all oviparous. Additionally, fertilization in all reptiles and birds occurs internally. 

● The offspring of reptiles, birds, and dinosaurs are miniature versions of the adults, and they do not change as they grow older.

● Dinosaurs, just like reptiles, had scaled dry skin. Birds also have scales on particular areas of the body, such as on their feet. 

Below are a few differences between dinosaurs and modern-day living organisms.

● Seemingly, dinosaurs were merely crocodiles that existed during a period when the earth provided favorable conditions to such living organisms to thrive. 

This idea implies that a crocodile that survived for a few centuries would grow into a dinosaur; this idea, however, does not seem correct. It is because the differences between modern-day organisms and dinosaurs are much more significant than they might seem. 

Below are a few fundamental and skeletal differences between birds, dinosaurs, and modern-day reptiles. 

● Most reptiles, like crocodiles and lizards, have legs that grow towards the side. In most cases, their thigh bones grow parallel to the ground. Consequently, most modern-day reptilian species move from side to side. 

● Dinosaurs, on the other hand, can stand upright with their legs right below their bodies because a dinosaur has a hole in its hip socket to permit this growth structure. Therefore, dinosaurs can run faster and with more endurance than most modern-day reptiles. 

● Modern-day birds have numerous modifications to adapt themselves for flight. For instance, birds have hollow bones and fragile skulls. A bird’s body is condensed into a more compact shape with the reptilian tail present in dinosaurs abandoned. Additionally, a bird’s pelvis has been strengthened a bit more to handle the shock of landing. 

I’ve researched information to write this article from many sources – multiple internet sites and magazines. However, some of the best reference knowledge is from books. If you are interested in checking out the best dinosaur books for adults on Amazon, you can find them by clicking here: Best Dinosaur Books for Adults

The 9 Closest Living Things to Dinosaurs

So let’s get into it, listing out the closest living things to dinosaurs. It will have to start with reptiles. Reptiles are a classification of tetrapod animals that include lizards, crocodiles, turtles, and snakes. 

Of this diverse family of modern animals, scientists believe that crocodiles hold the closest relations to the now-extinct dinosaurs. 

In fact, for more than twenty million years, the part of the globe that corresponds to modern-day South America was filled with two-legged dinosaurs, two-legged archosaurs, and two-legged crocodiles.

Modern taxonomy classifies all dinosaurs as reptiles because, among other things, they hatched from eggs, they existed in the Mesozoic Era – the age of reptiles.

Crocodiles

Crocodiles are large reptiles. Just like other archosaurs, crocodiles are diapsid (a group of tetrapods that have two holes on each side of the skull), even though they are reduced in size.

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Crocodiles are the closest related animals to dinosaurs – AdventureDinosaurs

Crocodilians are closely related to dinosaurs and birds more than most modern-day organisms because the family classification has features that relate more closely to other species. Both dinosaurs and crocodiles are grouped under the class Archosauria, which means chief or ruler + lizard (from Latin and Greek). 

Even though scientists do not consider crocodiles to be direct descendants of dinosaurs, as is the case in birds, the two sets of animals have multiple similarities. 

There are about twenty known crocodile species today, which reside in the tropics of Asia, Australia, Africa, and the Americas. 

Alligators

According to recent research (Source), alligators can create the same kind of neural maps of sound in the same way birds do. The scientists attributed this characteristic to the fact that both organisms shared a common ancestor: the archosaur. 

Alligators are considered closely related to dinosaurs because they are part of the crocodile classification. They share similar characteristics to crocodiles but are less closely related than true crocodiles.

Tuatara

The tuatara was recognized to have its own classification (and not as a lizard) in 2017, about 150 years since it was first classified as a lizard. 

The tuatara grows slowly, and they reproduce slowly. Tuataras live almost exclusively in New Zealand. Like lizards, they have the third eye at birth on the top of its head, but after 4-6 months, it is covered in scales and coloring, which makes it invisible unless you know where to look for it.

YouTube Video – Watch a Live Tuatara

YouTube Video by “It’s Ok to be Smart” which explains more in detail about the fascinating Tuatara

The tuatara is a reptile that can decapitate birds given its saw-like jaws. The animal lives to one hundred years old, and it can also remain alive in near-freezing environments. 

It is also the only remaining survivor of an ancient lineage of the first dinosaurs. 

Lizards

There is so much to say about lizards. There are multiple classifications, families, and suborders. 

Lizards are considered to be closely related to dinosaurs for many more things than just looks! With thousands of species in its classifications and families, a suggestion is to consider the similarities and differences between dinosaurs and lizards in the classification features.

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There are many different species and classifications of lizards – AdventureDinosaurs

The unique features of lizards, according to Wikipedia, “lizards make use of a variety of antipredator adaptations, including venom, camouflage, reflex bleeding, and the ability to sacrifice and regrow their tails.”

Birds

Interestingly enough, history dictates that birds might have evolved from Saurischian dinosaurs. 

This is because birds only started to emerge about 150 million years ago during the Jurassic age. Today, there are more than ten thousand bird species all over the world.

Secondly, some of the Saurischian dinosaurs had very light bones, they laid eggs, and they were covered in feathers. 

The Saurischian dinosaurs had so many characteristics in common with modern birds. 

Chickens

A comparison of contemporary living chicken species and the protein sequence derived from T-Rex collagen indicate remarkable similarities between the two (Source).  

From this comparison, it is found that chickens share numerous features, like fused clavicles, hollow bones, similar hip structures, feathers, and bones with air pockets. 

As a result, chickens might be closer to dinosaurs than alligators. Some scientists have even gone further to claim that chickens are modern dinosaurs. 

Turtles

A team of scientists recently reconstructed the tree of life as applied in turtles. 

The scientists generated considerable amounts of genetic data that significantly influenced the perceived evolutionary history for turtles. 

The scientists, therefore, placed turtles underclass ‘Archelosauria.’ This group consists of the animal’s closest relatives, like dinosaurs, crocodiles, and birds. 

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Falcons are related to the ancient flying reptile Archaeopteryx- AdventureDinosaurs

Falcons

The Archaeopteryx, the most famous fossil bird, looked similar to modern-day falcons. 

The Archaeopteryx might have existed 150 million years ago, and it indicated clear examples of transitional dinosaur species. The species displayed featured found in both dinosaurs and birds.

Falcons are considered related to dinosaurs due to classifications and family groupings of the Archaeopteryx.

Parrots

Scientists have often theorized that most bird species evolved from dinosaurs. 

Even so, scientists discovered fossil bones of a parrot-like dinosaur in 2009. 

Parrot-Dinosaur-related-to-Parrots-AdventureDinosaurs
Meet Psittacosaurus, the parrot dinosaur – AdventureDinosaurs

The Psittacosaurus dinosaur had a powerful curved beak, ate nuts and plants, walked on two limbs, and it had dagger-like claws. The species, which lived about 100 million years ago, is commonly referred to as the parrot dinosaur. 

Diving Deeper Into the Background on Dinosaurs and Dinosaur Relatives

Dinosaurs did not spring into existence until about two hundred million years ago. Just like other living things, they gradually and slowly evolved from previously existing organisms: the archosaurs. 

It was by following the rules brought forth by Charles Darwin regarding the natural selection and adaptation processes in living things. In looking for the closest living things to dinosaurs, we can follow Darwin’s processes too.

According to history, archosaurs were not very different from dinosaurs. However, they were much smaller than their descendants: the dinosaurs. 

Moreover, they had particular features that seemed to set them apart from dinosaurs. Most notably, the archosaurs did not have a locked-in posture for their hind and front limbs. 

Scientists might have identified a single archosaurs genus from which dinosaurs might have evolved: the Lagosuchus. Lagosuchus is Greek for rabbit crocodile. Such naming implies a quick and tiny reptile that might have scampered across forests in Triassic South America. Sometimes, the genus also goes by the name Marasuchus. 

Dinosaur Evolution During the Early Triassic Period

Interestingly, the archosaurs during the late and middle Triassic period did not evolve into dinosaurs alone. Isolated populations of these reptiles might have spawned the first crocodiles and pterosaurs as well. 

In fact, for more than twenty million years, the part of the globe that corresponds to modern-day South America was filled with two-legged dinosaurs, two-legged archosaurs, and two-legged crocodiles. 

Moreover, scientists often have a problem distinguishing between the fossil discoveries of these three separate families of animals. Paleontologists are not sure whether the archosaurs coexisted with therapsids – the mammal-like reptiles that existed during the late Permian period. 

Additionally, they remain unsure of whether the archosaurs survived after the Triassic Extinction Event that occurred two hundred million years ago. However, what remains clear is that dinosaurs might have gained the upper hand by the time the Jurassic period started. 

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The First Dinosaurs

The path of dinosaur evolution gets into sharper focus immediately if you shift your attention towards the Triassic Period and look at dinosaur species in South America and we may find some clues in determining the closest living things to dinosaurs.

During this period, the first dinosaurs slowly evolved into the tyrannosaurs, the raptors, and the sauropods we know today. 

The best candidate to suit the label of the first real dinosaur must be the Eoraptor. The Eoraptor was a South American, two-legged, and nimble meat-eater that is related to the Coelophysis that emerged much later in North America. 

The Eoraptors survived by consuming the smaller archosaurs, mammals, and crocodiles. Additionally, it might have only hunted during the night. 

The next crucial evolutionary event that followed the appearance of the Eoraptor might have been the split between the ornithischian dinosaurs (bird-like species), and the Saurischian dinosaurs (lizard-like species). 

This event transpired before the start of the Jurassic era. 

The ornithischian dinosaurs may have been the direct descendant of all herbivorous dinosaurs. Herbivorous dinosaurs include the ornithopods, ceratopsians, and the hadrosaurs. 

Meanwhile, the Saurichians split into two distinct families: the prosauropods and the theropods. The prosauropods are the bipedal, slender, and herbivorous dinosaurs.

These types of dinosaurs may have eventually evolved into titanosaurs and sauropods. Theropods are the carnivorous dinosaurs, such as the raptors and the T-Rex. 

More Evolution

The dinosaurian evolution continued to form its course even after these dominant dinosaur species were formed. However, according to recent paleontological research, the speed of dinosaur adaptation drastically slowed down during the Cretaceous period. 

During this period, dinosaurs were locked into existing species, and their rates of diversification and speciation slowed down considerably. 

A Deeper Dive Into Classification – What Science Says About Classifications of Dinosaurs

Modern taxonomy classifies all dinosaurs as reptiles. 

It is because, among other things, they hatched from eggs, they existed in the Mesozoic Era – the age of reptiles. However, there are more in-depth scientific data that aims at accurately classifying dinosaurs in light of both modern and traditional methods of classification. 

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Groupings of dinosaurs of the Ornithischian classification – AdventureDinosaurs

The ideal solution to this seemingly straightforward classification problem relies mainly on pre-determined taxonomy standards. 

The Traditional Approach

Traditional taxonomy dictates that animals must be grouped in light of their common characteristics. 

Common characteristics in reptiles include:

● Reptiles are ectotherms
● Reptiles lay eggs
● Reptiles are tetrapods

Arguably, most dinosaur species did not have all features found in the modern-day reptiles. 

However, scientists still considered them to hold enough reptilian characteristics to be considered as such. 

A Modern Approach

Modern taxonomy methodology classifies living organisms in light of their ancestry. 

Simply put, organisms that share a common ancestor are grouped together. 

This system is called phylogenetics. In this case, scientists would have to go many centuries back to find out which organism had the first reptile-like characteristics. This organism would then be considered to be the common ancestor for this group of animals. Consequently, scientists will classify all its descendants in one group. Therefore, to accurately apply the modern system of classification, we must have a look at dinosaur evolution.

Dinosaur Evolution

Amphibians gained the capability to lay eggs more than three hundred million years ago. Additionally, they developed a tough skin; this reduced their chances of drying out whenever they moved on land. 

With this evolutionary leap, amphibians gained the ability to survive on land as well as on water. Scientists consider these amphibians to be the earliest reptiles. Soon afterward, the first reptiles split into other branches, like snakes and lizards, archosaurs, turtles, and the swimming reptiles. 

The archosaurs, after that, split into dinosaurs, pterosaurs, and crocodiles. 

Therefore, in light of the phylogenetic method of classification, dinosaurs should be considered to be direct descendants of reptilian amphibians that had migrated from water bodies. 

Even though taxonomy prefers to consider dinosaurs as reptiles, one cannot ignore that some dinosaurs looked more like birds than other reptilian species. 

Why Birds Look More like Dinosaurs than Some Reptilian Species

One might suggest that birds are the closest living things to dinosaurs. Some scientists even argue that dinosaurs might have had feathers, they might have hatched from eggs, and they might have been warm-blooded. 

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Bird-like dinosaurs, or should it be stated “dinosaur-like birds” – AdventureDinosaurs

With these features in mind, some paleontologists argue that dinosaurs were birds. However, there is a considerable complication to this rationale. 

If you understand evolution history well enough, then you do realize that birds evolved from dinosaurs. This line of thought implies that they were no birds before dinosaurs. 

For that reason, how can we categorize dinosaurs as birds, yet there were no birds in existence before dinosaurs? Avian dinosaurs are, often, regarded to have been the first bird-like species. 

However, considering that not all dinosaur species were feathered or warm-blooded, it is very likely that there might have been an overlap between reptiles and birds. 

To answer the question, why do birds look more like dinosaurs than some reptilian species, we have to again look to the scientific classification of animals. Dinosaurs represent a very diverse group of reptiles, which might have emerged more than four hundred million years ago. 

The reptiles represent the dominant land species for more than two hundred million years until they were sent into extinction after a spatial asteroid hit the earth. 

Dinosaurs can be divided into two classes: Saurischia and Ornithischia. 

● Ornithischia represents a set of beaked, herbivorous dinosaur species. Members of this group might include the Iguanodon and the Stegosaurus species. 

● Saurischia represents all sauropods (herbivorous dinosaurs) and theropods (giant carnivorous dinosaurs). 

Interestingly enough, history dictates that birds might have evolved from the Saurischian species because birds only started to emerge about 150 million years ago during the Jurassic age. 

Secondly, some of the Saurischian dinosaurs had very light bones, they laid eggs, and they were covered in feathers. The Saurischian dinosaurs had so many characteristics in common with modern birds. 

Evolution takes time, and the transition from dinosaurs to birds might have taken millions of centuries. 

The most well-known fossil in this regard is the Archaeopteryx, which might have existed 150 million years ago. During this time, Europe might have been a collection of small islands placed in a warm tropical ocean. 

The Archaeopteryx indicated clear examples of transitional dinosaur species: they displayed features found in both dinosaurs and birds. 

Indeed, most of the Archaeopteryx fossils show evidence of some feather-like impressions. 

Additionally, since feathers were required to enable flight, the fossils provided evidence that the evolution had already started even before the Jurassic period came to an end. 

However, it must have taken a few million years before birds themselves started to diversify. For millions of years, birds had clawed wings and teeth. 

According to modern paleontology, modern birds must have appeared before the asteroid hit the earth: about 100 million years ago. While the bird-like species were, at that time, not the dominant species, it’s speculated that they were the only dinosaur species to survive the ordeal. 

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The Tuatara, a species that looks like a dinosaur and is related – AdventureDinosaurs

Conclusion

It’s not always straightforward to determine whether one species is related to another, as we can see from the dinosaurs. And, looks can be deceiving! 

Thanks to modern taxonomy and scientific classification, we can get closer to our understanding of which species are the closest living things to dinosaurs, and I’ve tried to cover that in this article.

Now, does a tuatara measure up as a close relative to a T-Rex or a Spinosaurus? If we are judging by looks, it has my vote! 

Lastly, if you or someone you know loves dinosaur toys, then check out my favorite dinosaur toy gifts on Amazon: Best Dinosaur Toys – Remote Control

Michael Haralson

I'm the owner of Adventure Dinosaurs website. Although I have an extensive business background, I am fascinated with dinosaurs and have been since childhood. I'm fortunate enough to have visited fossil museums in Europe (UK, Germany, and Spain), the US (California, Texas) and in Asia (China). Currently, I'm location independent with a home base in Kirkkonummi, Finland.

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