Paleontologists Identify New Species of Carboniferous-Period Shark

Paleontologists have identified a new genus and species of obruchevodid petalodont (petal-toothed) shark from multiple teeth unearthed at Mammoth Cave National Park in Kentucky, the United States.

The newly-identified shark species is believed to have swam in the Carboniferous-period seas 340 million years ago.

It belongs to the family Obruchevodidae within an order of extinct cartilaginous fishes called Petalodontiformes.

Scientifically named Clavusodens mcginnisi, the shark measured only 8-10 cm (3-4 inches) in length.

“Clavusodens mcginnisi’s name is derived from the shark’s back teeth which superficially look like old iron nails because of their flat crowns and long tooth bases,” explained first author Dr. John-Paul Hodnett and his colleagues.

“Nick-named ‘Chipmunk sharks’ for their small size and chisel-like front teeth and crushing back teeth, members of the Obruchevodidae were between 8 and 10 cm in length.”

“Their small size allowed them to avoid larger predators as they foraged on crustaceans, worms, and small brachiopods found along the sea floor.”

A number of small teeth of Clavusodens mcginnisi were found throughout the Ste. Genevieve Formation rock layer in Mammoth Cave National Park.

“The Ste. Genevieve Formation at Mammoth Cave is a layer of rocks that date back to approximately 340 million years ago,” the paleontologists said.

“The rocks consist of limestones and shales which formed on the bottom of a warm ocean reef.”

“The majority of fossilized sharks are found in invertebrate hash beds, a rock layer made of skeletal and shell parts of crinoids, blastoids, corals, gastropods, and brachiopods.”

“Prior to the discoveries made at Mammoth Cave over the last several years, no shark fossils were known from the Ste. Genevieve Formation.”

“To date, over 70 species of sharks and other fish have been identified from this geologic layer, including four new species.”

“The fossil discoveries in Mammoth Cave continue to reveal a wealth of new information about ancient shark species,” added Mammoth Cave National Park superintendent Barclay Trimble.

“Researchers and volunteers collected samples from the main Mammoth Cave system and from smaller isolated caves throughout the park that have provided new data on previously known ancient sharks and revealed several species that are brand new to science.”

“These discoveries help scientists to better understand the relationship and evolution of modern shark species within this relatively small geographic region.”

The discovery of Clavusodens mcginnisi is reported in a paper in the Journal of Paleontology.

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John-Paul M. Hodnett et al. Obruchevodid petalodonts (Chondrichthyes, Petalodontiformes, Obruchevodidae) from the Middle Mississippian (Viséan) Joppa Member of the Ste. Genevieve Formation at Mammoth Cave National Park, Kentucky, U.S.A. Journal of Paleontology, published online February 24, 2025; doi: 10.1017/jpa.2024.40