Archosauromorphs walked — across a 10,000-mile hellscape — so dinosaurs could run. 

According to a new study published in Nature Ecology and Evolution, archosauromorphs, early ancestors of dinosaurs and crocodiles, migrated across 10,000 miles of uninhabitable terrain after the end-Permian mass extinction event.

Using a new computer model, researchers from the University of Birmingham and the University of Bristol in the U.K. have conducted a geographical analysis to help determine how these prehistoric creatures dispersed across a changing environment. 

Extinct Reptile Migration

Early archosauromorphs resembled modern lizards and other reptiles. Some even looked like smaller versions of what would become dinosaurs. Prior to this study, researchers believed that during the early Triassic period, these creatures only survived in certain parts of the globe, as what was once the “tropics” was now unbearably hot and considered a “dead zone.” 

However, after the mass extinction event, archosauromorphs found a way to survive the dead zone. Researchers from this new study believe that archosauromorphs’ ability to migrate across the dead zone to other ecosystems would later lead to the evolution of dinosaurs. 

“Amid the worst climatic event in Earth’s history, where more species died than at any period since, life still survived. We know that archosauromorphs as a group managed to come out of this event and over the Triassic period became one of the main players in shaping life thereafter,” said Joseph Flannery-Sutherland from the University of Birmingham and a corresponding author of the study in a press release. 

Read More: How the Triassic Extinction Helped Dinosaurs Take Over the Planet

Tracking Fossil Evolution with the TARDIS

Because there were gaps in the archosauromorph fossil records, the research team had to think of a clever solution to fill in those gaps.

Using the new computer model, the team analyzed the phylogenetic tree — evolutionary tree — of archosauromorphs and compared it against dispersal routes that were based on landscape connectivity. The researchers called this TARDIS (terrains and routes directed in space-time).

“Gaps in their fossil record have increasingly begun to tell us something about what we weren’t seeing when it comes to these reptiles. Using our modelling system, we have been able to build a picture of what was happening to the archosauromorphs in these gaps and how they dispersed across the ancient world. This is what led us to call our method TARDIS, as we were looking at terrains and routes directed in space-time,” Flannery-Sutherland said in a press release. 

Thriving in the Triassic World

The model results were surprising. 

“Our results suggest that these reptiles were much harderier to the extreme climate of the Pangaean tropical dead zone, able to endure these hellish conditions to reach the other side of the world. It’s likely that this ability to survive the inhospitable tropics may have conferred an advantage that saw them thrive in the Triassic world,” Flannery-Sutherland said in a press release. 

Though we may not have been there to witness exactly how these creatures survived and evolved, this new information is a big next step in better understanding archosauromorph evolution. 

“The evolution of life has been controlled at times by the environment,” said Michael Benton from the University of Bristol and senior author of the study in a press release. “But it is difficult to integrate our limited and uncertain knowledge about the ancient landscape with our limited and uncertain knowledge about the ecology of extinct organisms. But by combining the fossils with reconstructed maps of the ancient world, in the context of evolutionary trees, we provide a way of overcoming these challenges.”

Read More: Why Dinosaurs Survived the Late Triassic Mass Extinction

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A graduate of UW-Whitewater, Monica Cull wrote for several organizations, including one that focused on bees and the natural world, before coming to Discover Magazine. Her current work also appears on her travel blog and Common State Magazine. Her love of science came from watching PBS shows as a kid with her mom and spending too much time binging Doctor Who.