Crocodiles are strange beasts, which seem to come from another time. Sometimes referred to as “Living fossils”, these cold, slow-moving, scaled reptiles have been around for hundreds of millions of years. A new study explains why their appearance has hardly changed since the Jurassic.
There are fossils from the ancestors of modern crocodilians (the group of reptiles that include crocodiles, alligators and caimans) that date back to about 200 million years ago. Today’s crocodiles and those that existed at the time of the dinosaurs all have a long flattened snout, an extremely powerful tail, very strong skin, and a similar way of moving, crawling or through their paws.
The fact that crocodiles have not physically evolved for such a long time is extremely unusual, especially given the great diversity that can be observed among animals today. Currently, there are only twenty-five species of crocodiles. Apart from a few variations in the shape of their skulls, all of them look very similar. However, when observing crocodile fossils, we notice that they were once much more diverse. Some could run fast, others swam in the ocean, and still others were burrowers or even bipeds, for example.
The theory of punctuated equilibria
Thanks to their recent research, scientists have finally discovered that the majority of crocodile species still in existence today evolve only very slowly. Experts explain this by the theory of punctuated equilibria. According to her, when organisms reach an optimal state, they do not evolve, until the environment forces them to adapt to new conditions. While it is still not very clear why some animals follow this pattern while others are constantly evolving, there are a few factors that could explain the phenomenon.
First of all, let’s remember that modern crocodilians are not able to control their body temperature. They are therefore more sensitive to variations in climate than other animals, such as mammals or birds, for example. However, crocodilians are able to survive without eating for very long periods of time, which makes them particularly resilient.
The evolution of crocodiles was probably due to a noticeable change in their environment to which they were forced to adapt, such as a large change in temperature. This could notably explain the disappearance of certain species of fossilized crocodiles.
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