Imagine walking along the rugged coast of Devon, the salty air whipping across your face, when your eyes fall upon a sliver of fossilized bone tucked into sandstone that has held its secrets for nearly a quarter of a billion years. At first glance, it looks like little more than a scrap of rock. Yet, hidden within it lies the story of one of the most successful groups of animals on Earth—the lepidosaurs, which today include over 12,000 species of lizards, snakes, and the enigmatic tuatara of New Zealand.
This is not just a fossil. It is a time machine. A relic from an age when dinosaurs had not yet taken their first steps and the world was still recovering from the greatest mass extinction in history. And now, thanks to a team of researchers at the University of Bristol, this ancient creature—newly named Agriodontosaurus helsbypetrae—is rewriting what we thought we knew about the origins of lizards.
The Triumph of the Lepidosaurs
Today, lepidosaurs are everywhere. From the geckos darting across your walls to snakes coiled in the undergrowth of tropical forests, they have conquered deserts, mountains, swamps, and islands. Their sheer diversity—greater than that of birds or mammals—raises an irresistible question: what makes them so successful?
Scientists have long believed the key lies in their skulls. Modern lizards and snakes possess hinged joints in their skulls that allow them to open their mouths wide enough to swallow prey much larger than their heads. They also have teeth not just along their jaws but on the roof of their mouths, allowing them to trap and subdue even the most slippery prey. Their skulls are light, flexible, and built for adaptation.
The tuatara, however, stands apart. Known as a “living fossil,” this reptile looks as though it has stepped straight out of the Triassic. Unlike its modern cousins, it retains a complete lower temporal bar—a bony bridge across the side of the skull—and wields a set of imposing teeth on its palate. To paleontologists, the tuatara has long seemed like a living clue to the earliest lepidosaurs. But the new fossil from Devon complicates that story.
A Fossil Full of Surprises
When paleobiology student Dan Marke and his supervisors began examining the specimen, they expected to find the classic early-lizard toolkit: palate teeth, a hinged skull, and the beginnings of flexible jaws. Instead, Agriodontosaurus helsbypetrae broke the rules.
It had no palate teeth.
It showed no sign of a hinged skull.
But it did feature an open lower temporal bar, a trait that links it with modern lizards and snakes rather than the tuatara.
Even more striking were its teeth—large, triangular, and dramatically proportioned compared to its relatives. They were not the delicate pins of an insect nibbler but robust weapons designed to pierce and slice through the armored shells of hard-bodied insects. In a world dominated by early reptiles and soon-to-emerge dinosaurs, this little hunter had carved out its niche with a set of formidable jaws.
Technology Unlocks the Past
To understand such a tiny fossil—the skull measures just 1.5 centimeters—scientists turned to cutting-edge technology. Conventional CT scans revealed much of the structure, but to see the teeth in detail required something even more powerful: synchrotron X-ray scanning.
At facilities in France and the UK, beams of intense light penetrated the fossil, capturing microscopic details without damaging it. The results were astonishing. With digital reconstructions, researchers could peel back the rock, virtually handling bones too fragile to be touched. What once seemed a fragment became a vivid portrait of a creature that lived 242 million years ago.
Professor Michael Benton, co-supervisor of the project, described the thrill: holding the entire skeleton in the palm of your hand, then seeing it come alive in exquisite digital detail. Suddenly, this fragile relic was no longer just stone—it was a predator, an insect-crusher, a pioneer of a lineage that would outlast empires of dinosaurs.
Naming a Fierce-Toothed Lizard
New species deserve names that honor their uniqueness, and this fossil was no exception. The team christened it Agriodontosaurus helsbypetrae—a mouthful, fittingly enough for a creature with such spectacular teeth. Translated, it means “fierce-toothed lizard from the Helsby rock,” a nod to the Helsby Sandstone Formation in Devon where it was unearthed.
Its discovery does more than add another name to the fossil record. It reshapes our understanding of how lepidosaurs began their evolutionary journey. Far from fitting neatly into the expected mold, this little reptile reminds us that evolution is messy, experimental, and full of surprises.
Life in the Triassic
To truly appreciate this fossil, we must step back into its world—the Middle Triassic, around 242 million years ago. Earth was recovering from the Permian mass extinction, an event that wiped out more than 90 percent of all species. Life was slowly rebounding, ecosystems reshuffling in unpredictable ways.
In this unstable world, small reptiles like Agriodontosaurus thrived in the shadows of early archosaurs—the ancestors of crocodiles and dinosaurs. They scuttled under ferns, hunted insects in the leaf litter, and experimented with forms and features that would one day explode into extraordinary diversity.
Unlike the later dinosaurs that would dominate the land, these early lepidosaurs found their advantage not in size or brute force but in versatility. The flexible jaws, venom in some species, and the ability to thrive in harsh climates made them survivors. The fossil from Devon offers a glimpse into the first steps of that evolutionary strategy.
A Living Legacy
Though the tuatara is often called a relic, the truth is richer. The discovery of Agriodontosaurus highlights that tuataras are not echoes of a single ancient species but members of a once-thriving, diverse group of reptiles. They, too, carry the evolutionary scars and successes of countless ancestors, including fierce little hunters like this one from Devon.
Today’s lepidosaurs—whether a python swallowing prey whole or a gecko clinging effortlessly to glass—owe their triumph to ancestors who experimented with skull structures, feeding strategies, and adaptability. The Devon fossil underscores how early those experiments began, and how creative evolution can be.
From Beach Find to Global Impact
The story of Agriodontosaurus helsbypetrae began not in a laboratory but on a beach. In 2015, fossil collector Dr. Rob Coram stumbled upon the specimen, scarcely recognizing its significance. That small discovery, made in a place that has yielded fossils for over 150 years, has now reshaped our vision of reptile evolution.
It is a reminder that science is built not just in vast laboratories but also on quiet moments of curiosity, on the careful eye that notices something unusual, on the dedication of students and mentors who devote years to teasing meaning from stone.
Why This Matters
Why should we care about a tiny fossil lizard from the Triassic? Because it is part of our story. Every bird soaring above us, every snake winding through grass, every lizard basking on a wall traces its lineage back to creatures like Agriodontosaurus. Understanding them is understanding the deep roots of life on Earth.
Moreover, fossils like this remind us of the fragile contingency of existence. If the ancestors of lepidosaurs had failed to adapt, we would live in a world without lizards, without snakes, without the extraordinary tapestry of reptilian diversity. The success of these creatures is a lesson in resilience, innovation, and survival across unimaginable spans of time.
A Glimpse into Eternity
As the scans revealed those triangular teeth, sharp even after 242 million years entombed in stone, one could almost imagine the little predator snapping at an insect, alive again in our minds. Fossils are not dead things; they are whispers of life, carried across oceans of time to reach us.
The discovery of Agriodontosaurus helsbypetrae is more than a scientific achievement. It is a testament to curiosity, patience, and the enduring human desire to know our origins. In every chipped bone, every carefully reconstructed skull, we find ourselves—not because we are reptiles, but because we too are survivors of deep time, inheritors of Earth’s endless experiment in life.
And so, from a Devon beach to the pages of Nature, this tiny fossil tells a story far larger than itself: the birth of a dynasty, the resilience of life, and the fierce little teeth that helped shape the world we know today.
More information: The oldest known lepidosaur and origins of lepidosaur feeding adaptations’, Nature (2025). DOI: 10.1038/s41586-025-09496-9
