Reptiles survived 'hellish' conditions during Earth's worst climate crisis

Life almost ended 252 million years ago. The end-Permian mass extinction wiped out 81% of marine life and over half of land-based species. But not everything perished. Among the survivors were the archosauromorphs, small early reptiles that would later give rise to crocodiles, dinosaurs, and birds.

These creatures were not supposed to survive the intense heat of the early Triassic tropics. Scientists considered this zone nearly lifeless.

Ancient reptiles crossed deadly zones

New research published in the journal Nature Ecology & Evolution reveals that archosauromorphs did more than endure the deadly zone. They moved through it.

Using a modeling system called TARDIS, which maps dispersal across time and space, researchers estimated the migration routes of 392 archosauromorph species.

The model linked fossils with landscape data and climate reconstructions, exposing hidden paths through so-called inhospitable regions.

Climate adaptability and niche expansion

The study showed that these reptiles had much wider climate tolerances than fossil evidence alone suggested. They adapted to extreme environments, including hot and dry zones with high temperature seasonality and low rainfall.

This ability to cross geographic and climatic barriers helped them enter new ecological niches. These movements likely shaped the evolutionary path that led to the rise of dinosaurs.

How ancient reptiles outlived extinction

“Amid the worst climatic event in Earth’s history, where more species died than at any period since, life still survived,” said Dr. Joseph Flannery-Sutherland from the University of Birmingham, who led the study.

“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.”

“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 modeling 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.”

According to Dr. Flannery-Sutherland, the results of the study suggest that these reptiles were much hardier 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,” he noted.

Tracking evolutionary radiation

The paper describes how the reptiles’ dispersal began in the northern supercontinent Laurasia. Over time, they crossed Central Pangaean mountains and entered southern Gondwana.

By the Wordian stage, long-distance movements had begun. These ancient reptiles not only traveled across land but also ventured into regions that lacked any fossil record. These regions were once thought off-limits.

The team found that climate conditions during these travels included both very high temperatures and arid environments. Their movement wasn’t random. It often followed low-elevation coastal routes, sometimes aided by monsoon-like humidity along ancient seashores.

“The evolution of life has been controlled at times by the environment, 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,” noted Professor Michael Benton, senior author of the study.

“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.”

Capturing the full story of reptiles

The oldest fossils were found in Europe, but that may reflect better sampling rather than true origins. The study’s models show that archosauromorphs could have existed elsewhere long before they appeared in the fossil record.

In fact, dispersal paths into South America and North America predate the oldest known fossils there by up to 15 million years.

By measuring climate variables along these ancient migration routes, the researchers captured broader ecological diversity than fossils alone could show. This reveals how species adapted as they moved through different environments.

Tracking other ancient animals

The authors suggest that similar modeling approaches could apply to other ancient lineages with poor fossil records. By coupling evolutionary trees with climate and terrain data, scientists can rebuild missing chapters of evolutionary history.

These early reptiles didn’t just bounce back from catastrophe. They reshaped their world through resilience and movement. Their journey laid the groundwork for the age of dinosaurs and ultimately modern birds and crocodiles.

The study is published in the journal Nature Ecology & Evolution.

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