The extinction of the dinosaurs is good news for snakes. According to new research, snake biodiversity began to increase shortly after the Cretaceous-Paleogene mass extinction, which was brought about by a large asteroid impact 66 years ago. Asteroids caused around 75 percent of all species, and all non-vian dinosaurs, to go extinct.
But the force gave the first snake species a chance and a chance to flourish, and they did. Currently, there are around 4,000 species of elongated, legless reptiles. To study this evolutionary change, a group of researchers examined the diets of extant snake species to gain insight into the past. “After the K-Pg extinction, (the snake) just got this big ecological explosion,” Michael Grundler, one of the paper’s authors and a postdoctoral researcher at the University of California Los Angeles, told Ars.
Rare fossils
Apparently, snake fossils are hard to come by. It’s rare to find any large snakes because their bodies are clean and can be painted quickly. “They are very rare in the fossil record. And when we find them in the fossil record, it’s usually just a few vertebrae, usually not really a skull, so we can’t really understand their biology,” Grundler said. “It’s not something like a big mammal or a big dinosaur with four arms and strong bones. With snakes, you have all these fragile vertebrae… their skulls are very well defined.”
Because of this, the team behind the new study began to make comparisons between the existing species. The researchers looked at dietary information from 882 living snake species—often found in museum collections—and used mathematical modeling to reconstruct their ancestral diets. It may seem difficult to learn about the ancestors of snakes millions of years ago from this, but Grundler says that, as long as we have good data on living organisms and their evolutionary relationships, it is possible to trace along their lines of descent.
According to the researchers’ model, the most common ancestor of all extant snake species was an insect. Before the mass extinction, there were probably snakes that ate rats and other animals. After the asteroid hit, however, it is possible that those animals died, although this is not certain, Grundler said. “What we get from the model is like a best guess,” he said.
(Somewhere even further back is also a common ancestor among snakes and other types of reptiles(but what it looks like and how it works is still up for debate, he said.)
An ancient story
After extinction, the remaining snakes flourished and divided into many different species. This is possible because, in the wake of the impact, many holes are left open. Also, more small vertebrate predators, like birds, to prey on. But with the diversity of snakes there is a growing diversity in terms of food—sometimes they are crazy big things like meat. “Today’s snakes have many interesting diets,” Grundler said. “They are all different from the same father.”
The study also suggests that the increase in snake biodiversity slows down many snake species as they move to their new habitats. However, species that arrive in new areas continue to adapt in different ways.
According to Grundler, this research can help us understand how families respond to environmental opportunities. It also adds to the body of research surrounding the history of snakes; another book published in September showed similar findings. “It also speaks to the importance of our natural history museums and collecting data on animals in nature,” he said.
PLoS Biology, 2021. DOI: 10.1371/journal.pbio.3001414 (About DOIs)