Ancient reptile Rhynchosaur died off before the dinosaurs due to weak teeth

A recent exploration into the prehistoric past by a research team from the University of Bristol has unveiled fascinating aspects about the Rhynchosaur, an ancient reptile that roamed our planet between 250 and 225 million years ago, predating the era of dinosaurs.

Rhynchosaurs are often clouded in mystery. Imagine ancient creatures, roughly the size of modern-day sheep, prevailing during the Triassic Period, an era characterized by its warm climate and hardy vegetation (see image here).

How researchers studied the Rhynchosaur 

To pierce this veil of obscurity, the Bristol team embarked on an investigative journey, scrutinizing specimens unearthed in Devon. They utilized cutting-edge CT scanning to examine the wear and tear on the rhynchosaur’s teeth as they munched through their meals, and to observe how new teeth were continually added at the back of the dental rows as the creatures grew.

The results, published in the latest edition of Palaeontology, reveal an intriguing yet grim aspect of these early plant-eaters’ lives. They would most likely starve to death in their old age as a result of the relentless wear on their teeth caused by tough vegetation.

“I was amazed to find that in many cases they dominated their ecosystems. If you found one fossil, you found hundreds. They were the sheep or antelopes of their day, and yet they had specialized dental systems that were apparently adapted for dealing with masses of tough plant food,” said Professor Mike Benton, the team leader from Bristol’s School of Earth Sciences.

Rhynchosaur fossils are a rare find

It was Dr. Rob Coram who discovered the fossils in Devon. “The fossils are rare, but occasionally individuals were entombed during river floods. This has made it possible to put together a series of jaw bones of rhynchosaurs that ranged in age from quite young, maybe even babies, through adults, and including one particularly old animal, a Triassic old-timer whose teeth had worn right down and probably struggled to get enough nutrition each day,” said Dr. Coram.

Thitiwoot Sethapanichsakul, who examined the jaws for his MSc in Palaeobiology, explained the wear patterns in more detail: “As the animals aged, the area of the jaws under wear at any time moved backwards relative to the front of the skull, bringing new teeth and new bone into wear. They were clearly eating really tough food such as ferns, that wore the teeth down to the bone of the jaw, meaning that they were basically chopping their meals by a mix of teeth and bone.”

However, there was a limit to this system. “Eventually, after a certain age – we’re not sure quite how many years – their growth slowed down and the area of wear was fixed and just got deeper and deeper,” said Dr. Coram.

“It’s like elephants today – they have a fixed number of teeth that come into use from the back, and after the age of seventy or so they’re on their last tooth, and then that’s that. We don’t think the rhynchosaurs lived that long, but their plant food was so testing that their jaws simply wore out and presumably they eventually starved to death.”

Played a crucial role in Triassic ecosystems

Rhynchosaurs served as a significant cog in the Triassic ecosystems as life reemerged from the world’s largest mass extinction that marked the end of the Permian Period. These creatures played a crucial role in this resurrection, setting the stage for new types of ecologies where dinosaurs, and later mammals, would reign supreme, thereby laying the groundwork for the modern world.

Upon comparing earlier rhynchosaurs, like those from Devon, with later ones from Scotland and Argentina, the researchers also unearthed how their dentitions evolved over time, facilitating two spurts of diversification in the Middle and then the Late Triassic. But these evolutionary triumphs ultimately found their terminus as changes in climate and available vegetation paved the way for dinosaurs to replace rhynchosaurs as the dominant species.

Incredibly interesting narrative emerged from the research results

The findings from this study take us on a deep dive into the life of a creature that has long since vanished from our planet, but whose story remains embedded in the rocks beneath us. It’s a narrative of success, adaptation, struggle, and ultimately, extinction – a sobering reminder of nature’s impermanence and the constant flux of life on Earth.

Yet, the importance of the rhynchosaurs goes beyond their own species. By studying them, we gain a broader understanding of the Earth’s history and the forces that have shaped it. 

From the debris of their downfall, a new world rose – a world of dinosaurs, and much later, a world dominated by mammals. The teeth of these ancient herbivores reveal not only the story of their lives and deaths but also the dawn of the world as we know it today.

Professor Benton’s fascination and admiration for these ancient creatures are clear. “I first studied the rhynchosaurs years ago, and I was amazed to find that in many cases they dominated their ecosystems.” That domination may be long past, but the legacy of the rhynchosaurs continues to be felt in the ongoing saga of life on Earth.

This research also reminds us that the world is not static. Species rise and fall, climates change, and life adapts. The extinction of the rhynchosaurs paved the way for the rise of the dinosaurs, who themselves would later give way to mammals. It’s a cycle that continues today, and by understanding it, we can better prepare for the changes still to come.

So, let us remember the rhynchosaurs – not just as the “sheep of their day,” but as crucial players in the grand tapestry of Earth’s history, serving a vital role in the ever-evolving narrative of life on our planet.

More about the Triassic period

The Triassic Period, occurring between approximately 252 million and 201 million years ago, marks the beginning of the Mesozoic Era, often referred to as the “Age of Dinosaurs”. However, the Triassic itself was a time of transition and recovery, following the end-Permian mass extinction event, the most devastating extinction event in Earth’s history.

Here’s an overview of what we know about the Triassic Period:

Life After the Mass Extinction

The Permian-Triassic extinction event killed off an estimated 96% of marine species and 70% of terrestrial vertebrate species. Life in the Triassic period, therefore, began with relatively few species. However, this allowed for a great deal of diversification and adaptive radiation, as species evolved to fill the ecological niches left vacant by the extinction event.

Flora

The Triassic saw the continued dominance of gymnosperms, a group of seed-producing plants that includes conifers. The first true mammals also appeared during this period. Ferns, horsetails, and ginkgo trees were prevalent, and it was during the Triassic that the first types of modern conifer trees emerged.

Fauna

This period saw the emergence and evolution of many significant groups of organisms. The first true mammals appeared during this period, as did the first dinosaurs. However, dinosaurs weren’t the dominant terrestrial vertebrates in the Triassic; this role was instead filled by other reptiles such as the aforementioned rhynchosaurs and various archosaurs. In the seas, fish continued to diversify, and marine reptiles like ichthyosaurs and nothosaurs became prevalent. The first flying vertebrates, the pterosaurs, appeared in the late Triassic.

Climate

The Triassic Period began in the aftermath of the greatest ice age known. The period was mostly hot and dry, and it had no ice caps at the poles. The interior of the supercontinent Pangaea was likely arid, with great seasonal fluctuations between hot and cold, given the vast distance from the interior of the supercontinent to the ocean.

Geology

The Triassic was a time of significant tectonic activity. The supercontinent Pangaea was still assembled, but the first signs of stress that would eventually lead to its breakup in the Jurassic started to appear. This included the rifting of the supercontinent along what is now the eastern coast of North America and the western coast of Europe and Africa.

Extinction

The Triassic period ended with another mass extinction event, the causes of which are still a matter of scientific debate. Climate change, asteroid impact, and volcanic activity have all been suggested as potential culprits. This extinction led to the dominance of dinosaurs in the ensuing Jurassic Period.

This is a brief overview and, as with all areas of paleontology, our understanding of the Triassic period continues to evolve as new discoveries are made and existing data is reinterpreted. By examining the fossil record, scientists can piece together a picture of what life might have been like during this important period in Earth’s history.

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