SCIENCE: The asteroid that wiped out the dinosaurs gave life to snakes.

“Snakes are one of the most successful groups of tetrapods, which is somewhat ironic, since the key feature of tetrapods (Tetrapoda means “four-legged” in Greek) is no longer present in these reptiles today. “says Dr Nick Longrich of the Milner Center for Evolution at the University of Bath in the UK.

Some primitive snakes, ancestors of modern ones, had legs, according to previous research by Longrich, who in a 2015 study analyzed the first known fossil of a four-legged snake, the ‘Tetrapodophis amplectus’, which lived during the Lower Cretaceous. in the territory now occupied by Brazil.

Dr Longrich is part of a team of researchers from the University of Bath (www.bath.ac.uk) who have just discovered that modern snakes evolved from a handful of ancestors who survived the asteroid impact that triggered the extinction of the dinosaurs, in a phenomenon he called “creative destruction”.

“Snakes are incredibly diverse and today, with over 4,000 living species, they are the most species-rich group of reptiles,” Longrich continues.

According to this scientist, one could suppose that the origin of this diversity is ancient, dating back to the first appearance of snakes at the time of the dinosaurs, more than 100 million years ago, but “in reality, modern snakes seem to have a much more recent origin,” he says.

Longrich explains that “fossils and DNA (genetic material) suggest that modern snakes spread across the planet following the mass extinction caused by an asteroid impact in the late Cretaceous,” the study found. of Bath.

Its authors argue that after this devastating impact, the snakes took advantage of ecological “niches”, i.e. the environment in which they lived and interacted with other beings and the environment, previously occupied by their competitors, and occupied the habitats that were vacant. , after the probable extinction of 90% of all species on Earth.

The research used fossils and analyzed genetic differences between modern snakes to piece together the evolution of these reptiles, finding that they began to diversify when this extraterrestrial impact took place, which wiped out the dinosaurs and most of the living beings.

THE REPTILES THAT HAVE CONQUERED THE WORLD.

The authors say the ability of the snakes, some blind and worm-like, to burrow underground and spend long periods eating insects or even without food helped them survive the destructive effects of the impact. .

Later, the extinction of their competitors – including Cretaceous snakes and the dinosaurs themselves – allowed the snakes to move into new ecological niches, habitats and continents.

The snakes then began to diversify, producing lineages such as vipers, poisonous cobras, garter snakes, huge pythons and boa constrictors, exploiting new habitats, such as trees and the sea, and feeding on new prey.

The fossils analyzed by the Bath researchers show a change in the shape of the snakes’ vertebrae in the post-impact period, and the appearance of new groups of snakes, including sea giants up to 10 meters long.

“It’s extraordinary because snakes not only survived an extinction that wiped out so many other animals, but over a few million years they innovated and used their habitats in new ways,” said Dr Catherine. Klein, lead author of the study. .

The study also suggests that snakes began to spread around the world around this time.

For Dr Longrich, co-author of the research, extinction could have acted “as a form of ‘creative destruction’, since by ending ancient species, it allowed survivors to exploit gaps in the ecosystem, experimenting with new ways of life”. and habitats”.

Zanzibar blind worm snake (photo Nick Longrich)

NATURE DESTROYS AND LATER CREATES.

“This seems to be a general evolutionary feature: in the periods immediately following the great extinctions, more experimental and innovative evolution emerges,” he says.

“The destruction of biodiversity is making life even more diverse than before,” Longrich points out, noting that “patterns observed in snakes indicate a key role for disasters – severe, rapid, global environmental disruptions – in driving the evolutionary change.

“Many groups of animals and plants show patterns similar to snakes,” Longrich told Efe.

“Mammals show a massive adaptive phenomenon after the asteroid impact, and we observe in a later period, around 10 million years, the appearance of the first horses, bats and whales, as well as primates modern, our ancestors” he underlines.

“Among birds, new species appeared after the mass extinction, such as penguins, owls and ducks. And, among fish, tuna, flatfish and swordfish appeared,” he adds. .

“Butterflies, sunflowers and daisies that didn’t exist in the Cretaceous, as well as grasses and ants, which did exist but weren’t really important until then, seem to have evolved after the asteroid impact” , he concludes.

Pitviper Snake Gloydius intermedius, from the Gobi Desert in Mongolia. (Nick Longrich)

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