Prehistoric Sharks Discovered at Mammoth Cave, Among Other Scientific Surprises

The rolling landscape of Kentucky’s Green River Valley, home to Mammoth Cave National Park, may not seem like the kind of place where sharks could live. But 325 million years ago, this site was home to at least 40 different shark species. In honor of National Fossil Day, the paleontology team at the National Park Service, under the direction of Senior Paleontologist Vincent Santucci, is sharing evidence of the numerous sharks the team has identified, including at least six species that are brand new to science.

This is just one of several recent findings at national park sites that have brought scientifically significant research to light, thanks to the active inventory work and ongoing monitoring of Santucci and his small team. I have long admired the passion and dedication of these staff, who make it possible for us to experience the parks in a way that transcends space and time and stretches the imagination, as the landscapes we know today are nothing like they used to be.

These three remarkable findings give us a glimpse of the distant past and the reasons why people like me are fascinated by fossils.

 

1. Humans walking alongside giant ground sloths at White Sands National Park, New Mexico

The unique landscape at this park encompasses rolling dunes of sand made up of a rare form of crystallized gypsum. It’s a hot, monochrome environment that lacks the obvious presence of life, which is probably why the region was selected to be a nuclear missile testing range in the 1940s. But these dunes are not lifeless. During the Ice Age, which lasted from 2.5 million years to 11,700 years ago, this area was home to a large body of water called Lake Otero. The lake fed a thriving community of plants and animals, and as it dried, it created the perfect conditions to preserve imprints of the creatures that once lived here. Ten years ago, a Park Service staff person helped uncover numerous prints in the deposits of the lake, including Columbian mammoths, camels, dire wolves and saber-toothed cats, and this discovery is now the largest collection of fossilized Ice Age footprints in the world.

In 2018, scientists also discovered the longest known set of human footprints in the world from this time period, which stretches nearly a mile long. Santucci himself discovered what appears to be a toddler’s footprints interspersed at intervals alongside those of an adult, suggesting a mother sometimes carrying and sometimes walking alongside her child. The team has not yet shared the expected age of these footprints, but we know that the prints are in the same location as those of giant ground sloths, now-extinct mammals that grew to the size of elephants — and that the sloths reacted to the human tracks. Columbian mammoth tracks were also found in the same location. We knew humans were around at the same time as Ice Age megafauna but know little about the coexistence between these species. This research could teach us more about how people lived thousands of years ago. The team also discovered other artifacts in the basin, including weapons, tools and tool-making remains that were made after the tracks.

Santucci notes that several tribes are associated with White Sands, and the footprints his team helped find would have belonged to their ancestors. “This is a real time preserved between people that had thoughts and emotions,” he said. “This research would not have been discovered without proactive inventory work,” he added, stressing the importance of assessing and monitoring the fossil history at each site within the park system.

 

2. A scene scarier than “Jaws” — and set underground — at Mammoth Cave National Park, Kentucky

A 3D model of the 330-million-year-old Glikmanius shark fossil by the National Park Service Geologic Resources Division, one of numerous remains found at the park from this time period.

If you’ve lived near the ocean, you’ve probably seen the sharks’ teeth that sometimes wash up along the shore. Because sharks have so many teeth that they shed regularly as new ones grow in, they are more common than other fossils and remains. But imagine finding a large quantity of these teeth in modern-day landlocked Kentucky — in a cave. Now you can brag! In November 2019, that is just what a team of Park Service experts and external specialists accomplished.

The sheer diversity of animals the team found is remarkable. At least 40 different shark species and their relatives ended up at Mammoth Cave 325 million years ago, including six species never before discovered. Beyond the significance of each individual specimen, scientists uncovered evidence of an entire ecosystem from this time period, known as the Mississippian Period, preserved throughout the cave system. Scientists also discovered something rare: not one, but two partial shark skeletons. Because they are made of cartilage, which tends to decompose quickly, it is unusual to find shark skeletons in fossilized form. The discoveries stunned scientists and can ultimately help us understand how these animals lived and coexisted with other living things in their environment.

A geologist passed through narrow cave openings in a hard-to-access location of the park to capture images of many of these skeletons. These images were eventually converted to 3D models using advanced software technology. Although the public can’t go to the remote cave area to see the findings in person, these photographs and high-tech artistic renderings will be part of a new exhibit at the site where visitors can learn more about these remarkable aquatic predators and what the region was like when they lived here long ago.

 

3. Prehistoric dolphins at George Washington Birthplace National Monument, Virginia

Our nation’s first president was born in 1732 in a house on the marshy shores of Popes Creek in Virginia’s Tidewater region. Today, the Park Service preserves the foundations of George Washington’s first home, a replica of the original structure, a memorial, and a family cemetery at the site. In March 2020, staff found more pieces of history here that predate the president’s home by millions of years — and they did so simply by walking along the Potomac River.

As staff surveyed cliffs along the river, they noticed what appeared to be bones poking from the soft sediment. Santucci and his team helped uncover dolphin remains from the Miocene epoch estimated to be about 15 million years old. The paleontologists quickly got to work casting the remains and preparing them for shipment when they found the nearly complete skull of a second dolphin on the same day. Both skeletons were vulnerable to being swept away and lost, so teams worked rapidly to remove the remains, which now reside at the nearby Calvert Marine Museum in southern Maryland for study. Researchers believe the animals are part of an extinct family of long-nosed dolphins (Eurhinodelphinidae).

This surprise discovery underscores the importance of inventorying and monitoring sites across the park system to help uncover new findings where researchers may least be expecting them. While many people wouldn’t think of a president’s home as being a prime site for fossils, the potential for a discovery was already on the team’s radar thanks to prior work surveying the site.

 

Two-thirds of the 421 national park sites contain paleontological wonders of some kind, including sites with “in situ” remains — those still in their natural setting — as well as those with museums and other collections. Only 18 parks were originally designated to preserve prehistoric artifacts, yet 277 have known fossils. The recent addition of Mill Springs Battlefield National Monument in Kentucky to the National Park System could soon bring that total to 278 — and what the team might find there is anybody’s guess.

“We have less than 10 paleontologists managing over a billion-year record of life preserved within the National Park System,” said Santucci, noting that his team helps preserve everything from 1.5-billion-year-old algae at Glacier National Park to more recent creatures such as American lions and saber-toothed cats at sites such as Tule Springs National Monument.

His team tells the story of life on Earth using park resources that span many eons, epochs and eras. So much of the work is made possible through chance — for a fossil to have been at the right place at the right time to be preserved, and for a researcher to be at the right place at the right time to discover it. Each fossil provides a brief and irreplaceable snapshot of another time, and even after decades of work spanning millions of years, there is so much yet to learn.

Find out more about National Fossil Day on the Park Service website, including a downloadable coloring book and junior ranger program for kids and a special feature on Permian Reef fossils at Guadalupe Mountain National Park in Texas.