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Are Alligators Dinosaurs (Not Really, but Almost!)

Alligators are not dinosaurs, but they are related to dinosaurs because they share the same ancestor. This ancestor is the archosaur. It is an extinct clade of birds and crocodilians. From here, the dinosaurs and crocodilians split millions of years ago. 

Dinosaur
Alligators are descended from archosaurs, the common ancestor of modern reptiles, dinosaurs, and birds.

The archosaur is the common ancestor of the dinosaurs and alligators. Archosaurs are reptiles, and its name literally means “ruling reptiles.”

Where Did Alligators Come From? 

Alligators came from the Brachychampsa Montana. It was a freshwater reptile that best represents that modern alligator. It was carnivorous, and the first fossil was found in Montana’s Hell Creek Formation. The creek was an ancient location that formed at the end of the cretaceous period. 

The Brachychampsa Montana is an extinct species, and it is one of the earliest versions of the modern alligator. The alligator’s ancestors lived 245 million years ago. It was only 80 million years ago that the modern crocodilians appeared, and they did not change much. 

It was during this period, 80 million years ago, that the Brachychampsa Montana appeared. While all these are happening, the ancestors of the crocodiles and caimans also evolved. 

The Brachychampsa Montana had short teeth despite having a large mouth. Its fossil gives scientists clues as to what it ate. Some suggest that it must have had a diet of turtles as these animals were known to be common during the time in which these early Alligators existed.

This alligator was about the same size as the modern ones. Unlike other ancient species, they are not giants. They are about three metres long but far from supergiants like the sarchosuchus.

Lolong the Crocodile - Skeleton
Although they share a common ancestor, alligators are not considered dinosaurs

Why Alligators Aren’t Considered Dinosaurs

Alligators are not considered dinosaurs because they belong to separate branches of the evolutionary tree, even though they share a common ancestor. In addition, crocodilia and dinosaurs have specific characteristics that help set them apart.

Some features that differentiate dinosaurs from alligators:

  • Upright stance – dinosaurs could stand on their hind legs or on fours. Their legs are perpendicular to their bodies. Alligators, on the other hand, have limbs sprawled to the sides. 
  • Hole in the Skull – all dinosaurs have a hole in the skull. The hole is between the eye sockets, and some have two holes behind the eye socket. These holes helped the dinos regulate their body temperature.
  • Pelvic Bones – dinosaurs have three or more special bones in the pelvis called sacral vertebrae. 

There are some common denominators between alligators and dinosaurs. For example, both of them lay eggs. As far as the scales or scutes are concerned, that remains to be an issue of debate. 

Emu
The closest relatives of dinosaurs are modern bipedal birds like Ostriches and Emus.

Did Alligators Live With Dinosaurs?

The early ancestors of alligators and crocodiles have been around since the time of the dinosaurs.

Dinosaurs rose in the Middle Triassic Period, which was 230 million years ago. At that time, they were nothing more than reptiles, among many. There were so many reptiles in that period that the dinosaurs were not at all special. 

By the end of the Triassic period, they dominated earth because of their sheer size and number. In the Late Triassic Period, their competition got wiped out by an extinction event. It gave the dinosaurs more access to food. 

Dinosaurs went extinct about 65 million years ago, which means that they lived with alligators—considering that the earliest crocodiles have been around since 80 million years ago. 

Is an Alligator a Reptile or a Dinosaur?

Alligators and dinosaurs are both reptiles, however, an alligator is not a dinosaur.

The image of dinosaurs that many people know today is heavily contested. They may not look like crocodiles or alligators at all. Recent discoveries now show that dinosaurs are likely to have had feathers and not scales!

As scientists discover more evidence that dinosaurs are more closely related to birds than alligators, they begin to realize that dinosaurs may have looked more like birds than modern reptiles.

Crocodile in the sun
The ancestors of modern Crocodiles and Alligators were alive at the same time as the dinosaurs.

Were There Prehistoric Crocodilians?

There are only 25 species of crocodilians today, and this includes the alligator. In prehistoric times there were many kinds of alligators and crocodiles that have since gone extinct.

They died and went extinct because of certain changes in their surroundings. There were even vegan crocodiles, and some were huge monsters that lived in the sea. There were also huge crocodiles that were capable of eating dinosaurs.

Alligators did not evolve that much despite millions of years. They are not living fossils, they are a class of their own. 

As of today, the modern crocodilian family is comprised of four subfamilies. These are the crocodiles, alligators, caimans, and gharials, all of which are considered reptiles.

A Gharial in dark water
Alligators, crocodiles, caiman, and gharials are the four modern crocodilians

Are Alligators Leftover Dinosaurs?

Alligators are not leftover dinosaurs. They share a common ancestor, but even when dinosaurs roamed the earth, crocodiles and alligators belonged to a separate and distinct evolutionary branch than dinosaurs.

Dinosaurs and alligators lived together. And since alligators, crocodiles, caimans, and gharials did not come from dinosaurs, crocodilians are not leftovers of the most powerful reptiles that lived in the world.

Summary

Alligators are not dinosaurs. Dinosaurs and alligators come from the same ancestor, the archosaur. From the archosaur, the reptiles split into groups. One group lead to the evolution of the dinosaurs, and then another to the crocodilian family.

Alligators, crocodiles, caimans, and gharials are “cousins.” They have no relationship whatsoever, and it is a misnomer to call them living fossils or living dinosaurs. 

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