Crocodiles have been around for millions of years, and while they are often thought to be relatively constant creatures since their origins, two new studies reveal that they actually have a rich and varied evolutionary history.
In one study, researchers were able to trace the origins of crocodile morphology — a larger component of the crocodile population and their now-extinct relatives — in Europe about 145 million years ago. Later, somewhere in North America, the taxa further split into two groups, crocodiles and alligators, which could tolerate saltwater and those that could not.
"It appears that the ability to cross saltwater bodies allows the crocodile to be more widely distributed around the world, including tropical oceans, than the alligator, which is confined to freshwater and unable to reach some areas. Professor Paul Barrett, a paleontologist who works at the Natural History Museum in London, explained in a statement.
The second paper examines how quickly it is possible for ancient crocodiles to grow up. In contrast to our impression of modern crocodiles moving slowly and growing slowly, it turns out that their ancient relatives are exactly the opposite. Researchers have found signs of high-speed growth in fossil bone structures, suggesting that they grow quickly and move quickly♂️
Of course, modern crocodiles also become swift when it comes to hunting, but other than that, they seem to be more inclined to a slower-paced life. Why this shift?
"The first question is: Is the slower growth due to the aquatic habits of the crocodiles, or did they have them earlier?" Barrett said. "Second, during the evolution of crocodiles, when do they turn off the high metabolism of their ancestors and re-evolve into a state similar to a more primitive slow growth?"
Fossil evidence has uncovered a smaller, active, terrestrial ancient relative that grew at a rate similar to that of extant crocodile populations, which may rule out the aquatic theory. Researchers suggest that slow growth may be a result of living in a low-resource environment, although this is still up for debate.
In any case, this study may change the image of crocodiles that are often thought of as lazy creatures that are not subject to change. "Crocodiles and their relatives are really trying a lot of different ways of life," Barrett said. According to paleontologists, some ancient crocodile group members were carnivores like their descendants, but preyed on dinosaurs, while others were vegans – plant crocodiles, who would have thought?
The findings were published in two issues, the Royal Society Public Science Journal and Current Biology.
This clip shows the ancient crocodile's vegetarian relative, the Seamus crocodile
“They’re doing a surprising number of things. This is in great contrast to what we know about living crocodiles, which are all predators limited to living in the tropics with semi-aquatic or amphibious lifestyles.”
“Living crocodiles are really a pale shadow of the diversity that they and their relatives had in the past.”
“We’re learning new things about them all the time.”