New Cretaceous Shark Species Discovered in South Dakota

A new species of freshwater shark that lived about 67 million years ago (Cretaceous period) has been identified from fossilized teeth found in South Dakota.

An illustration showing what Galagadon nordquistae would have looked like in life, swimming along the river floor. Image credit: Velizar Simeonovski, Field Museum.

Named Galagadon nordquistae, the newly-discovered shark species once swam in the Cretaceous rivers of what is now South Dakota.

It was a small freshwater shark (12 to 18 inches, or 30.5-45.7 cm, long), related to modern-day carpet sharks such as the ‘whiskered’ wobbegong shark.

Its tiny teeth — each one measuring less than a millimeter across — were discovered in the sediment left behind when paleontologists uncovered the bones of ‘Sue,’ currently the most complete T. rex specimen ever described.

“The more we discover about the Cretaceous period just before the non-bird dinosaurs went extinct, the more fantastic that world becomes,” said Dr. Terry Gates, lecturer at North Carolina State University and research affiliate with the North Carolina Museum of Natural Sciences.

“It may seem odd today, but about 67 million years ago, what is now South Dakota was covered in forests, swamps and winding rivers.”

“This shark lived at the same time as Sue the T. rex, it was part of the same world,” said Dr. Pete Makovicky, curator of dinosaurs at the Field Museum.

“Most of its body wasn’t preserved, because sharks’ skeletons are made of cartilage, but we were able to find its tiny fossilized teeth.”

“Galagadon nordquistae was not swooping in to prey on T. rex, Triceratops, or any other dinosaurs that happened into its streams. This shark had teeth that were good for catching small fish or crushing snails and crawdads,” Dr. Gates added.

“It amazes me that we can find microscopic shark teeth sitting right beside the bones of the largest predators of all time. These teeth are the size of a sand grain. Without a microscope you’d just throw them away.”

The study also reflects the importance of learning about fossils beyond big, flashy dinosaurs.

“Every species in an ecosystem plays a supporting role, keeping the whole network together,” Dr. Gates said.

“There is no way for us to understand what changed in the ecosystem during the time of the mass extinction at the end of the Cretaceous without knowing all the wonderful species that existed before.”

“Most people, when they think of fossils, think of big huge dinosaur bones, but in the dirt, there are the bones of tiny animals,” said Field Museum volunteer Karen Nordquist.

“When you get those bones and identify them, you get an idea of the whole environment — everything that lived with the big dinosaurs. You learn so much from microsorting.”

The discovery is described in the Journal of Paleontology.

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Terry A. Gates et al. New sharks and other chondrichthyans from the latest Maastrichtian (Late Cretaceous) of North America. Journal of Paleontology, published online January 21, 2019; doi: 10.1017/jpa.2018.92