Everyone loves a good ancient creature discovery and this one packs quite the visual punch – at least if you know a thing or two about arcade games. The ancient shark is described by the authors as having teeth that resemble the spaceships in the 1980s game Galaga. Admittedly, it’s a stretch, but now that they mention it, they do kind of resemble alien vessels...

The species has been named Galagadon nordquistae – the second half of which honors Karen Nordquist, a volunteer who helped discover the teeth after sifting through almost 2 tons of dirt.

"Once the Field Museum received the T. rex specimen, they began to prepare the fossils, and instead of following typical procedure of throwing away the sediment that surrounded the bones, Bill Simpson (the fossil vertebrates collections manager) decided to keep it until someone came along who was interested in studying any small fossils that might be discovered in the sediment. That was me!" said lead author Terry Gates, lecturer at North Carolina State University, to IFLScience.

"We had a lot of matrix to sort," Nordquist added, "and we did it a teaspoon at a time looking carefully at every piece to pick out the bones from the dirt. It is a long slow process. Near the end of this project I saw a very small piece and as I moved it I got a glimpse of a shiny surface. When that happens, you think tooth. As I looked closer, it looked like a baby shark tooth."

More than two dozen teeth, each the size of a sand grain, were eventually found in leftover sediment in the Hell Creek Formation of South Dakota. Their tiny chompers were part of a much bigger, mightier dinosaur discovery: the most complete T. rex specimen ever described, intimidatingly named Sue.

"This is actually a very cool thing, because if you think about it, Sue the T. rex died in a river, then was buried by sand and mud flowing with the current," said Gates. "Because the fossils of Galagadon were found right alongside the bones of Sue, we know that T. rex and this new shark lived near one another. It is uncertain if they ever interacted with one another, though."

 

Around 67 million years ago, this little shark was busy feasting on small fish and crushing snails and crawdads. The newly named freshwater carpet shark belongs to the Orectolobiformes order and is approximately 30 to 46 centimeters long (12 to 18 inches). The study is published in the Journal of Paleontology.

The team note that the ancient shark is comparable in size to bamboo sharks living today, it had a flat face, and was likely camouflage-colored, similar to its current relatives. When Galagadon wasn’t eating, it was probably spending a good amount of its time lounging on the bottom of the riverbed.

"We were able to find three unique features to our teeth, and a total of nine characteristics that defined Galagadon," said Gates. "For instance, if you look at the broad side of the Galagadon tooth crown, every one has some type of ornamentation on it, they are not just flat. The presence of these bumps, folds, and ridges are quite useful in dividing shark species."

The site likely represents a point bar deposit within a meandering river channel, based on the evidence of alternating mud-rich sediment layers with leaf fossils and sandy siltstone. 

"What makes me really excited about finding a shark of this type in a freshwater ecosystem is that it is another example of a world gone by in which many species of the group called carpet sharks occupied rivers and streams around the world," said Gates. "At some point between the end-Cretaceous extinction and today, all of the carpet sharks living in rivers and streams went extinct. The bamboo shark today is known to go into water that is a mixture of fresh and saltwater, but does not live solely in freshwater."

Gates emphasized that Nordquist deserves a lot of recognition for her contribution to this discovery, which is why the team named the species for her.

"I was totally surprised and honored to be recognized in this way," said Nordquist. "I never imagined that a new species would be named for me."