Why crocodiles survived devastating asteroid strike that wiped out dinosaurs

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Crocodiles survived the asteroid strike that wiped out dinosaurs


Crocodiles survived the asteroid strike that wiped out the dinosaurs because they hit on a winning formula and have hardly changed since, according to new research.

They can thrive in or out of water and live in complete darkness as well as being very robust and can survive terrible injuries.

It was 66 million years ago that a city-sized space rock smashed into the Gulf of Mexico killing off the biggest and most successful land animals that ever lived – the dinosaurs.

How the crocs survived has puzzled scientists for decades. Now a British team has found it was thanks to their lack of diversity.

They look very similar today to ones from the Jurassic period – some 200 million years ago.

Their slow evolutionary rate is due to arriving at a shape that was versatile and efficient enough to cope with a severe global catastrophe.

How the crocodiles survived has puzzled scientists for decades

Lead author Dr Max Stockdale, of the University of Bristol, said: “This could be one explanation why crocodiles survived the meteor impact at the end of the Cretaceous period, in which the dinosaurs perished.”

He added: “The crocodiles landed upon a lifestyle that was versatile enough to adapt to the enormous environmental changes that have taken place since the dinosaurs were around.”

Crocodiles can hold their breath underwater for up to an hour owing to a remarkable ability to retain oxygen. They can also move about on land with surprising speed – particularly when alarmed or angry. There are very few species alive today – just 25.

On the other hand there are thousands of varieties of some animals such as lizards and birds which have been around the same amount of time – or even less.

A Meteor glowing as it enters the Earth's atmosphere
The asteroid smashed into the Gulf of Mexico

Dr Stockdale and colleagues found the reason is crocodiles have a ‘stop-start’ pattern of evolution – governed by environmental change.

The phenomenon described in Nature Communications Biology is known as ‘punctuated equilibrium’. It explains the prehistoric types we don’t see today.

They included giants as big as dinosaurs, plant-eaters, fast runners, diggers and burrowers and serpent like monsters that lived in the sea.

The rate of their evolution is generally slow – but occasionally they evolve more quickly because the environment has changed.

In particular, it speeds up when the climate is warmer – with their body size increasing.

Dr Stockdale, a geographical scientist, said: “Our analysis used a machine learning algorithm to estimate rates of evolution.

The crocodiles have had a much greater diversity of forms in the past
The crocodiles have had a much greater diversity of forms in the past

“Evolutionary rate is the amount of change that has taken place over a given amount of time, which we can work out by comparing measurements from fossils and taking into account how old they are.

“For our study we measured body size, which is important because it interacts with how fast animals grow, how much food they need, how big their populations are and how likely they are to become extinct.”

Crocodiles generally thrive better in warm conditions because they cannot control their body temperature and require warmth from the environment.

The climate during the age of dinosaurs was warmer than it is today. That is why there were many more varieties of crocodile around then.

Being able to draw energy from the sun means they do not need to eat as much as a warm-blooded animal like a bird or a mammal.

Asteroid falling from the sky during dinosaurs apocalypse and extinction day
Crocodiles outlived dinosaurs by some 66 million years

Added Dr Stockdale: “It is fascinating to see how intricate a relationship exists between the earth and the living things we share it with.”

The researchers now plan to find out why some types of prehistoric crocodile died out, while others didn’t.

Crocodiles have been dubbed the ‘ultimate survivors’. Having arisen some 200 million years ago, they have outlived the dinosaurs by some 66 million years.

They have also seen off two ice ages. Even humans, the most fearsome predators ever to stalk the Earth, have failed to force any species into extinction.

The latest study backs a theory put forward more than 20 years ago – suggesting their endurance is down to a unique design.

They are extremely tough and robust – and have immune systems that can sustain terrible injuries.

In territorial fights they commonly tear each other’s legs off. They go away and sulk for a while – and then heal up. They also routinely live for decades.

In commercial captivity they have been shown to be able to survive in complete pitch black.

The nuclear-winter triggered by the meteor-impact that made the dinosaurs extinct would be a similar scenario – it would be dark all the time.





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