Crocodiles are not dinosaurs, but all dinosaurs and crocodiles share a common ancestor, and crocodiles have been around since the time of the dinosaurs.
While some people argue that crocodiles are dinosaurs, it is not true. What can be said is that they have the same ancestors, but then the split made them different from each other.
Are Crocodiles Descendants of Dinosaurs?
Crocodiles are not descended from dinosaurs. Instead, both crocodiles and dinosaurs are descended from the same common ancestor called the archosaur.
Archosaur means “ruling reptiles.” They have sub-classes that include pterosaurs. Many of these are already extinct, and some descendants made it to the Triassic Period.
There were no crocodiles at the dawn of the Mesozoic Era or the Triassic Period. However, there were dinosaurs already. This period lasted for 37 million years.
The archosaurs from which the crocodiles are descended looked like crocodiles, but their nostrils were on top of their head. These archosaurs ate marine organisms.
True archosaurs had two branches. These are pseudosuchia, where crocodiles belong, and Ornithischia, which includes dinosaurs and birds.
In the Triassic Period, many pseudosuchian groups went extinct. However, one specific group, the crocodylomorphs, survived the major extinction.
This group went on to produce the crocodile of the modern-day. Living crocodiles from this group are the crocodiles, alligators, caimans, and gavialids.
What Makes a Dinosaur a Dinosaur?
Dinosaurs are a group of reptiles. They lived sometime about 240 million years ago. There are many types of dinosaurs, and some are so huge, like the Spinosaurus. Some are also small, like the Microraptor, which is the size of a chicken.
A dinosaur has straight back legs. It is what makes a dinosaur a dinosaur. What this means is that “dinosaurs” that lived in water are not true dinosaurs.
Because of the leg position, the dinosaur succeeded before the extinction event. The legs were perpendicular to their bodies, like I humans. It was easier for them to move around and use less energy. Their upper bodies also received support from their legs.
Dinosaurs are also reptiles. At that time, there were hundreds, if not thousands, of other reptiles. Some flying creatures that looked like dinosaurs were also reptiles, but they were not dinosaurs.
Here are the main characteristics of dinosaurs:
- Upright stance; their legs are perpendicular with the body
- They laid eggs
- They lived on land, not the sea; some species lived by the sea like the ancestors of penguins
- There was a hole in their skull found between the eye socket and the nostril
Reptiles that did not have an upright stance were never part of the dinosaur family. As such, crocodiles are not dinosaurs, but they came from the same ancestor.
Did Crocodiles Live With Dinosaurs?
Yes, crocodiles lived with dinosaurs. Crocodiles have been around for 240 million years, while dinosaurs were also present about 99 million years ago. At that time, there were more species of crocodiles than there are today.
Here are some types of crocodiles that lived with dinosaurs:
- Sarchosuchus – an extinct genus that lived in the Cretaceous period. It lived about 133 million years ago, and the estimate is that it grew up to 30 feet and weight 3.5 metric tons.
- Deinosuchus – the name means “terrible crocodile.” It lived between 82 million and 73 million years ago. The first remains were found in the United States. It grew up to 35 feet and weight up to five metric tons.
- Shieldcroc – an ancient giant crocodile whose fossils were found in Missouri in the United States. It had an armor-plated head, and it lived about 95 million years ago. They are smaller than their counterparts, as they only grew up to 16 feet.
Even the modern crocodile of today lived with ancient dinosaurs. The modern crocodile has not evolved for over 200 million years. Fossil remains of ancient crocodiles show that they have not changed.
Did Crocodiles Evolve?
Every animal is constantly evolving, however, crocodiles have not evolved significantly for hundreds of millions of years. However, a recent study revealed that the modern crocodile is evolving more quickly.
In the study, scientists found out that modern crocodiles in Asia, Australia, are evolving. They are beginning to look similar, not because of ancient traits, but because they evolve the same skull shapes as time passes.
Scientists also noted that some ancient crocodile fossils look similar to current species of crocs. While it may validate that they did not evolve much at all, some changes are happening.
What experts did was compare the skulls of 24 living crocodylian species against 19 fossil relatives. They used a method called geometric morphometrics. Then, they created three-dimensional models of the skulls and measured how the anatomy changed over time.
Evidence of Crocodile Evolution
Earlier in 2021, a palaeontologist, Stephanie Pierce, reported that some lineages had been rapidly evolving for the past two million years. For example, they found out that modern crocodiles now seem to develop the same skull shapes.
The Nile Crocodile of Africa and the Morelet’s Crocodile in Central America have evolved to have the same skull shape, but they are not even close evolutionary relatives.
The broad-snouted caiman has a similar skull shape to the extinct Voay. It is not that the current species have not changed, but it seems to be going back to the kind of skull that was effective for some of its ancestors.
Summary: Are Crocodiles Dinosaurs?
Crocodiles are not dinosaurs. Both are reptiles, but they evolved from different branches of the reptile family. Both crocodiles and dinosaurs are descended from archosaurs. Dinosaurs are more closely related to birds than to crocodiles.
Crocodiles and dinosaurs lived together, but crocodiles have not evolved significantly for over 200 million years. Recent studies, however, show that the modern crocodile is evolving more quickly.
Stuart is the editor of Fauna Facts. He edits our writers’ work as well as contributing his own content. Stuart is passionate about sustainable farming and animal welfare and has written extensively on cows and geese for the site.