This extinct species of turtles survived the asteroid that killed the dinosaurs

TORONTO -- Sixty-six million years ago, an asteroid slammed into the Earth and wiped out 70 per cent of all life -- but while the dinosaurs perished, a species of turtle measuring only 60 cm long survived.

Laurasichersis relicta is the name of this plucky species of land turtle, the subject of a new paper published in Scientific Reports last week. Pieced together from fossilized shell fragments found in France, it is believed to be the only turtle to survive the extinction in this area of the world, according to Spanish paleontologist Adán Pérez García, who spent 10 years studying the concept.

The turtle lived in the land masses that made up Laurasia, a prehistoric supercontinent in what is now the Northern Hemisphere, a press release states.

Scientists were already aware that horned turtles in the prehistoric supercontinent of Gondwana -- located in today’s Southern Hemisphere -- had managed to survive the extinction event that wiped out the dinosaurs, according to fossils found in Oceania and South America. These turtles, called “meiolaniids”, lived to encounter humans, who then hunted them into extinction, according to the press release.

But the new discovery of L. relicta is the first evidence of a species of turtle in the Northern Hemisphere that also clung on through the mass extinction of the dinosaurs.

How did it do it?

Pérez García has no idea.

"The reason why Laurasichersis survived the great extinction, while none of the other primitive North American, European or Asian land turtles managed to do so, remains a mystery," he said in the press release.

Many species perished in the wake of the asteroid strike not merely because of the impact itself, but how the environment changed. According to the press release, the Earth underwent “a spiral of gas emissions, molten material and acid rain that caused a sudden warming of the climate and transformed the landscapes in which the turtles lived.”

The fauna and flora had to change rapidly, and that included the turtles that lived in the Northern Hemisphere. Most died off, and were replaced by new groups arriving from various places to occupy the areas that are now North America, Africa and Asia, the press release states.

Scientists previously thought that all of these land turtles that settled in the area after the extinction event belonged to the two lineages that would evolve into present day land turtles. Pérez García’s research confirms that L. relicta developed independently of these turtles, and of the Gondwanan varieties.

It actually hails from another region of the world completely, according to Pérez García.

"It is the last representative of a group previously identified in China and Mongolia, where it was known since the Jurassic, more than 100 million years before the new European Laurasichersis turtle existed,” he said.

Pérez García knew the fossils he was inspecting belonged to a different species than other Cretaceous era turtles because of how different the shell looked when pieced together. According to the press release, the shell had a “complex structure,” made up of many plates -- including a uniquely large number of plates on the underside of the turtle, or the “ventral shell region.”

Like other primitive turtles, L. relicta couldn’t retract its head into its shell, and had developed extra protective armour around its extremities as a result.

All of the fossils of L. relicta analyzed are housed in the Paleontology Collection of the Muséum national d’Histoire naturelle in Paris.