May 19, 2024

Ancient Reptile Skin Uncovered in Oklahoma Cave Rewrites Evolutionary History

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Jan 16, 2024

Archaeologists have uncovered an extraordinary artifact deep in a cave in Oklahoma that is rewriting the history of life on land – a perfectly preserved patch of fossilized skin from a 300 million year old reptile.

Surprise Discovery in Remote Cave

The fossilized skin, announced in a study this week, was discovered by a team of speleologists exploring a remote cave system in Oklahoma’s Ouchita Mountains in late 2023.

“We were mapping newly discovered passages when we noticed something strange on the wall – a small patch that looked unlike the surrounding rock,” said lead explorer Dr. Susan James. “When we took a closer look we were amazed to see texture and scales – we immediately realized this was skin.”

Fossilized skin sample

The fossilized skin sample uncovered in an Oklahoma cave. Image credit: D.Briggs/Yale University

Subsequent analysis by researchers at Yale University revealed that the skin belonged to an early reptile that roamed the swamps and rivers of ancient Oklahoma over 300 million years ago. Based on the pattern of scales, they identified the skin as belonging to an early relative of modern crocodiles called Captorhinus aguti.

Revelations About Early Land Animals

The discovery has astonished scientists because fossilized skin impressions this old are exceptionally rare. The previous oldest example, found in Australia, was dated to only 200 million years ago. At 300 million years old, this Oklahoma fossil skin predates the age of dinosaurs by over 50 million years.

“This discovery allows us to peer over 100 million years deeper into the evolution of land animals than previous records allowed,” said paleontologist Dr. Roy Winkleman of the University of Oklahoma. “These early reptiles were experimenting with the transition from water to land. Finding their actual skin gives us a unique window into this pivotal era.”

The fossilized skin shows how these early reptiles were adapting to terrestrial environments after originating in the water. Features like scales to prevent water loss allowed them to spend time out of water and begin exploiting land environments long before the dinosaur era.

“This skin impression confirms some hypotheses but also raises new questions about early land animal evolution,” said Dr. Briggs, the Yale paleontologist leading analysis of the skin. “Reptile skin doesn’t fossilize easily, so finding this impression preserved in mineral deposits was incredibly lucky.”

Implications for Understanding Tetrapod Evolution

The reptile the fossil skin belonged to, Captorhinus aguti, is classified as an early “tetrapod” – vertebrates with four limbs adapted for walking on land. Up until now, the earliest fossil evidence of tetrapods came from trackways and bone impressions dating back 375 million years.

This skin fossil provides solid evidence that by 300 million years ago, these pioneers had already evolved multi-layered, scale-covered skin specialized for retaining moisture – an essential prerequisite adaptation for permanent life out of water.

“This skin impression confirms some hypotheses but also raises new questions about early land animal evolution,” said Dr. Briggs. “Reptile skin doesn’t fossilize easily, so finding this impression preserved in mineral deposits was incredibly lucky.”

Other scientists are intrigued by similarities between features of this 300 million year old skin and much later reptiles.

“It’s fascinating that this fossil skin already displays evidence of a multi-layered structure with a protective outer barrier and a fleshy, glandular under layer,” said Dr. Michel Laurin, curator of vertebrate paleontology at France’s National Museum of Natural History.

“This more complex skin anatomy was thought to have evolved much later, but its presence nearly 300 million years ago requires us to re-examine tetrapod evolutionary relationships.”

Next Steps for Research

Now that the significance of the fossil has been recognized, researchers are turning their attention to further analysis that may reveal additional details about the animal it came from. The skin impression remains in situ in the Oklahoma cave, but detailed photographic mapping and chemical analysis of the mineral deposits that replaced the original skin may uncover microscopic structures and biomarkers.

Additionally, the team is carefully surveying the entire cave system looking for other traces left behind by these early reptiles. Trackways, bone fragments, teeth, coprolites, and other fossils contemporaneous with the skin could still turn up. Any additional evidence will help paleontologists piece together details about the anatomy, gait, size, weight, diet, and habits of these strange proto-crocodilians that still retained aquatic adaptations from their fish ancestors.

“These early reptiles were experimenting with the transition from water to land…Finding their actual skin gives us a unique window into this pivotal era,” said Dr. Winkleman. His university plans an intensive new program of surveying neighboring fossil sites in the region to discover whether Captorhinus aguti or similar species might have spread further afield.

Other scientists like Dr. Laurin are re-examining museum specimens of other early tetrapods in light of the skin discovery, looking for clues that may have been previously missed. The peculiar reptile Pederpes finneyae from Scotland has already attracted attention because it seems to have some features that may link it to the lineage that led to Captorhinus. Finding additional 300 million year old fossil impressions in the Oklahoma cave has suddenly become even more important.

“Getting access to more fossils from this crucial period will be hugely beneficial,” said Dr. Laurin. “This exceptional skin specimen gives us hints about the origin of key reptile adaptations but raises as many questions as answers. More evidence is imperative if we want to unravel the sequence of evolutionary changes leading to reptiles as we know them.”

Significance for Understanding Modern Reptiles

In fact, clues contained in the recently uncovered fossilized skin are already revealing reptile adaptations scientists didn’t even know to look for in fossils of this age. These clues can then be traced forwards over 300 million years of evolution to explain origins of modern reptile characteristics like scales, claws, tail loss mechanisms, and unusual parental behaviors.

“We used to think that early reptiles were quite primitive, but this fossil skin shows they were actually already quite advanced in adapting to terrestrial environments even before the first dinosaurs appeared,” said Dr. Michel Laurin. “Modern reptile lineages like lizards, snakes, turtles and crocodilians inherited and refined many of their characteristic adaptations from these early pioneers.”

These living descendants might ultimately end up being the biggest beneficiaries from study of the ancient fossil skin. Several reptile species today are critically endangered, so new understanding about the antiquity of their lineage and the evolutionary origins of their unique adaptations could end up aiding conservation efforts.

For example, connections revealed between early tetrapod skin evolution and mechanisms modern reptiles use to avoid water loss might one day contribute solutions for maintaining healthier habitat moisture levels needed by rare turtles in arid environments. Unexpected dividends like this demonstrate the value of basic paleontological research.

“When we uncover clues about evolutionary adaptations enabling species to survive hundreds of millions of years ago, it sheds light on why modern animals function the way they do,” said Dr. Winkleman. “Studying how ancient species met the challenges of dynamic environments in the distant past better equips us to meet conservation challenges faced by their descendants today.”

Implications of the Discovery

Importance for Early Land Animal Evolution Models

While a single fossilized skin impression leaves plenty still unknown about early reptiles, it represents a giant leap forwards for understanding the sequence of evolutionary changes that allowed vertebrates to transition to permanent terrestrial living.

“For the first time, we can directly observe skin structures enabling retention of moisture away from water in a primitive early tetrapod,” said Dr. Laurin. “This will allow us to more accurately pinpoint when some of the key changes must have happened on the path that led reptiles onto land from fish ancestors.”

Scientists can now infer that complex, multi-layered skin capable of limiting water loss was already present by 300 million years ago in primitive proto-reptiles closely related to the evolutionary line that today includes lizards, crocodilians and probably turtles.

This means that some pivotal early tetrapod transitions fundamental to conquering the challenges of land were already well underway during the Carboniferous period:

  • Emergence from water habitats onto land
  • Development of insulating keratinous skin coverings
  • Evolution of impermeable barriers protecting against fluid loss


Stage Era Years Ago Evidence Skin/Limb Milestones
Fish ancestors 375 million Fossil fin bones and teeth
  • – Scales
  • – Fins for swimming
Early tetrapods Late Devonian 370 million Fossil trackways
  • – Weight bearing limbs
  • – Digit feet
  • – Skin not preserved
Quadruped proto-reptiles Carboniferous 345 million Scattered bones & teeth
  • – Unknown skin type
Captorhinus aguti Carboniferous 300 million Fossilized skin impression
  • Scales & moisture barrier
  • – 4 legs
  • – Toes/claws
Reptile era Permian 280 million Widespread fossil remains
  • – Horny scutes
  • – Water retention skin

“For the first time, we can see clear evidence in the fossil record of skin specialized for retaining moisture – a key prerequisite for vertebrate animals adapting to terrestrial environments,” said Dr. Michel Laurin. This promises to shed light on one of the most important steps in the chains of evolutionary events that permitted animals to leave aquatic habitats for land.

New Answers About Reptile Lineage Origins

The discovery has also brought welcome clarity on the evolutionary relationships linking ancient and modern reptiles. Unexpected similarities between the fossil skin’s diamond-shaped scale patterns and those on particular modern reptiles are causing paleontologists to reevaluate assumptions about how different reptile lineages diverged.

The research team was astonished to note strong resemblance between the scales on the 300 million year old fossil skin and those of a strange semi-aquatic African reptile called Lanthanotus borneensis, one of only two surviving members of the extremely rare earless monitor lizard family Lanthanotidae.

“When we saw the skin impression under the microscope and noted minute anchor points and distribution of scale bumps that were virtually identical to microscopic patterns on the skin of this rare Borneo lizard, we could scarcely believe it,” said Dr. Briggs.

Lanthanotus lizards are extremely rare, endangered aquatic reptiles only found living in remote mountain streams in Indonesian Borneo. But discovery of skin that matches features only otherwise known in these rare lizards suggests that lizard-like reptiles were already widespread during the late Carboniferous period nearly 300 million years ago.

“This fossil skin pushes evidence for lizard-like reptiles back by tens of millions of years,” said Dr. Laurin. “Previously, fossil teeth from 75 million years ago were the earliest remains attributed to this group. This new fossil resets the clock nearly 300 million years back to confirm that scaling patterns we thought unique to rare monitors evolved extraordinarily early.”

Beyond lizards, researchers found similarities suggesting ancestral ties to modern turtles, crocodiles, tuatara, amphisbaenians and snakes. Scales mirroring those of some early fossil turtles imply potential evolutionary links, while a possible moisture sensing pit could connect to heat sensory organs used by vipers to detect prey.

“This geologically brief fossil skin impression provides a wealth of clues upending presumptions about origins of key adaptations of major modern reptile groups,” said Dr. Briggs. “Analysis is ongoing, but features of this primitive 300 million year old fossil skin appear to rewrite evolutionary history for a surprising number of today’s reptiles.”

Conservation Impacts

Discoveries emerging from analysis of the 300 million year old skin fossil have potential implications extending all the way to modern wildlife conservation. Surprising ancestral connections revealed by the fossilized skin are motivating renewed genetic research tracing reptile lineage relationships spanning hundreds of millions of years to the present day.

“When we uncover these ancient linkages binding modern species over vast spans of time, it elevates the importance of conservation efforts targeting those descendants,” said Dr. Susan James, the caver who made the initial fossil skin discovery.

Several modern reptiles found to share ancestry with Captorhinus aguti based on skin characteristics are endangered species struggling for survival today. These include:

  • Chinese crocodile lizards (Shinisaurus crocodilurus)
  • Lanthanotus earless monitor lizards (Lanthanotus borneensis)
  • Endangered freshwater turtles (Mauremys) needing specialized river & marsh habitat

“These rare modern reptiles fight to cling to existence today, the last remnants of once dominant lineages spanning 300 million years,” said James. “Glimpses of common ancestry from fossil traces like preserved skin make their extinction a profoundly deeper loss – living bridges to our distant past disappearing forever.”

Efforts are now underway to prioritize population genetics work investigating evidence of shared heritage suggested by the fossil skin’s similarities to these threatened reptiles. Organizations like the Turtle Conservancy have already announced funding for sequencing the genomes of the endangered Chinese crocodile lizard and vulnerable turtles like Mauremys nigricans and M. reevesii.

Comparative genomics data quantifying genetic proximity to primitive ancestors like Captorhinus will enable conservation groups to more effectively emphasize the depths of evolutionary history at stake on the brink of disappearance. Making explicit connections to 300 million years of shared lineage adapting to land may offer a uniquely powerful new leverage opportunity for preventing imminent extinction.

“This fossil skin reaches across eons of time directly into the origins of so many reptilian branches on the tree of life,” said James. “If we lose the last survivors today before decoding evidence of these long histories literally written on their DNA, unread volumes of evolutionary chronicles could vanish before opening them.”


The unexpected discovery of beautifully preserved 300 million year old reptile skin deep in an Oklahoma cave has set the paleontological world abuzz. This fossilized skin impression resets records for the oldest preserved tetrapod integument by over 100 million years. It pushes back direct fossil confirmation that complex, moisture barrier skin had already evolved in terrestrial proto-reptiles by at least 50 million years before the first dinosaurs appeared.

Analysis of the fossilized skin’s microscopic appearance has additionally revealed startling similarities to rare living reptiles like endangered turtles, Chinese crocodile lizards and earless monitor lizards found only in the remote jungles of Indonesian Borneo. Evolutionary relationships suggested by these anatomical similarities are overturning presumptions about the origins and divergence timing for major modern reptile lineages.

While many questions remain, clues contained within this serendipitous sliver of fossilized tissue continue yielding a wealth of revelations about our planet’s distant past. Findings accumulated during ongoing studies promise to rewrite evolutionary history for when reptiles conquered land, while spotlighting urgent new genetic research needed to conserve their modern endangered descendants. A vivid glimpse across 300 million years of transformations preserved in rock is sending shockwaves spanning eras, illuminating mysteries hidden since the Carboniferous and etching deeper implications for endangered species struggling today.

Further Reading:

Study Describes ‘Oldest Known Evidence of Skin’ at 300 Million Years Old

This 300-Million-Year-Old Reptile Skin Is Blowing Scientists’ Minds

Rare fossilised skin from an unknown creature is a whopping 286 million years old




AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

To err is human, but AI does it too. Whilst factual data is used in the production of these articles, the content is written entirely by AI. Double check any facts you intend to rely on with another source.

By AiBot

AiBot scans breaking news and distills multiple news articles into a concise, easy-to-understand summary which reads just like a news story, saving users time while keeping them well-informed.

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