Scientists Find Sharks Older Than Dinosaurs Hidden in Stone for 325 Million Years

You would never think this is a place where sharks might be lurking. The air is motionless, as if it is afraid to stir. Light barely penetrates, and everything seems heavy, as if stuck in place, disconnected from the natural movement of the water. Down in the depths of Mammoth Cave, a different tale is told in a voice barely above a whisper, a whisper of conspiracy.

In 2025, researchers working through sections of limestone began noticing something small but unusual. Tiny fossil teeth. Fragments at first are easy to overlook. But once studied closely, they pointed to something much larger. Two entirely new shark species.

According to findings released by the National Park Service, one of them was named Clavusodens mcginnisi. It was no giant predator. In fact, it measured only a few inches long. Its teeth suggest it fed on small, slow-moving creatures like worms and crustaceans along the seafloor.


The second, Macadens olsoni, stood out for a different reason. Its fossil showed a curved tooth structure designed for crushing prey. Not tearing, not slicing. Crushing. A small but clear sign that even ancient sharks were experimenting with how to survive.

These discoveries came from the Ste. Genevieve Formation is a layer of rock formed roughly 340 million years ago. Back then, this entire region was covered by a shallow sea. What is now a cave system was once part of a living, shifting marine environment.

The concept takes a second to sink in. The narrow trails may appear quiet and pedestrian these days, but in the distant past, these waterways were constantly in motion. Life forms existed where rock is solidly situated today, feeding and adapting to a world that is constantly changing.

A Record That Reframes the Past

What makes this discovery particularly striking is not so much who this species is but where it fits into the grand scheme of things. The National Park Service’s fossil project in the depths of Mammoth Cave has unearthed over 40 different shark species from the past, some of which have yet to be named, leaving only teeth and fragments of spines behind after the cartilage that once connected them vanished.

Shark skeletons are rarely preserved. Their bodies are mostly soft tissue, which breaks down quickly. But in rare conditions, like those found in Mammoth Cave, even three-dimensional skeletal structures can survive. Fossils of species like Glikmanius and Saivodus striatus have been recovered in forms that allow researchers to study them in detail.

That level of preservation alters the way one looks at these creatures. Rather than trying to put the pieces together with the little bits one can find, one can start to see structure, form, and variation with greater clarity.

The geological context is important. USGS studies have shown that the Ste. Genevieve Formation is an ancient carbonate platform, a shallow marine environment that is rich in life. Such a setting is typical of a wide variety of life forms, ranging from small invertebrates to the first fishes. This is seen in the fossil record.

Different tooth shapes suggest different diets. Different body forms suggest different roles in the ecosystem. It was not a simple food chain. It was layered, complex, and constantly shifting.

These two newly discovered sharks actually fit into the bigger picture quite nicely. They are little cogs in a massive machine; however, they are cogs in a place where there were once gaps.

What these small fossils are telling us

It is quite easy to get distracted by the idea of new species and go off on a tangent. Each fossil adds a point of reference. A way to understand how life adapted over time. The variation between these sharks suggests that even hundreds of millions of years ago, survival was not about size alone. It was about specialization.

Finding the right food. Using the right method. Conserving energy. Those patterns feel familiar, even now.

There is still so much to uncover in the cave. With new surveys and tools such as imaging and mapping, researchers are exploring the cave in new areas that were previously difficult to access. Instead of removing large chunks of rock and stone from the cave, the new approach is to observe and document all that is seen. It is a new and gentler approach that provides greater insights.

The National Park Service now reaches out to the public through visual reconstructions and models so they can see these fossils, which are not directly accessible. It takes what is hidden and makes it accessible to the public without disturbing the habitat in which this specimen remained preserved.

Mammoth Cave is not just a place, but a living archive, which is changing over time. Not everything is visible at once. Not everything is fully understood. But layer by layer, the picture becomes clearer.

What catches the eye, however, is not only their age but how they still speak to us. A tooth. A strand. A shard embedded in stone. Individually, they do not amount to much. Collectively, however, they bring back to life an ocean that died hundreds of millions of years ago.