20 Jul Ancient Teeth: Shark Fossils from Mammoth Cave
During my 12-week internship, I’ve been able to experience a variety of projects related to science and resource management here at Mammoth Cave National Park. From biological surveys of cave critters, to learning the process of banding a bird, most of these experiences have been brand new to me, especially the Paleontology related activities.
My focus this summer was on a diverse collection of Paleozoic chondrichthyan (cartilaginous fish) fossils, collected from Mammoth Cave’s passages. The collection contains more than 70 species belonging to shark and ratfish groups, alive 340-325 million years ago. During this time, a shallow sea covered what is now Kentucky, and the sea floor was rich with crinoids, sponges, corals, and other ancient animals: such as huge sharks. Since that age life continued to expand, and continents continued to move, and soon conditions for this land would favor erosion.
This summer I’ve spent a good chunk of my time in the cave, imagining the paleo ocean environment while visiting the limestone passages. I’ll admit, the scene I picture looks a lot like this paleo art by Julius Csotonyi. Though, when I encounter water in the cave, I can’t help but fast-forward hundreds of millions of years later to see a waterbody over the Girkin Limestone, beginning to carve Mammoth Cave’s upper passages about 10 million years ago. By this time, most of North America was above sea level as it is today. Witnessing underground rivers continue to carve their way through rock feels like a blessing when you’re in the cave system.
My goal as a Paleontology Assistant was to create a digital record of the shark and ratfish fossils in the NPS Museum database, and to learn as much as I could relating to these shark fossils. I know the whole data entry aspect may not sound exciting to most people, but gaining experience with handling, describing, measuring, and color-coding the collection by taxonomic group was wonderful. Through the museum cataloging process, I’ve experienced an amazing introduction to paleo studies, and I aim to continue learning more relating to paleo environments after this internship.
The assembly of shark fossils at Mammoth Cave is quite impressive, being one of the most diverse Late Mississippian (335-340 million years ago) shark faunas found in North America. Paleontology discoveries in the park include (but not limited to) a very interesting, not yet scientifically described cranial cartilage of a massive shark, Saivodus striatus. Saivodus can be seen in the center of the paleo art above, as the central shark on the ocean floor and the massive shark lurking in the background.
Recently, I received the opportunity to visit the Saivodus specimen in situ and record measurements for the paleontologist working with Mammoth Cave to identify and describe the cartilaginous fish fossils! It was a remarkable experience to see the cartilage of this shark preserved in the fossiliferous limestone passage. I was even able to collect a tooth from the passage, along with sediment samples and measurements of the Saivodus cartilage. This visit brought me right back to the paleo ocean Csotonyi depicts. I found myself in the water with these creatures, trudging along the ocean floor millions of years ago.
As my internship comes to an end, this will likely be the activity I miss most, visiting the paleo ocean that today is known as Mammoth Cave’s Passages. With the love I’ve found for caving with the Cave Research Foundation and the tranquility felt when picturing this paleo environment, I intend on returning to Mammoth Cave National Park to continue growing my mental reconstruction of the paleo ocean, preserved in the cave passages.