Scientists discovered a 310-million-year-old shark nursery in Northeastern Illinois' Mazon Creek where the prehistoric Bandringa species would have lived.

The researchers told the Los Angeles Times a freshwater sea once existed in the American Midwest where the sharks laid their eggs. They published their work in the Journal of Vertebrate Paleontology.

The Bandringa sharks are known for their distinct long-nosed snout and for their pre-dinosaur existence. In 1969, scientists found the fossilized sharks, but the specimens only measured four to six inches in length. Initially, they were believed to be a smaller species, but were later revealed to be juvenile Bandringa sharks.

"When you account for the different preservation modes, there is nothing that distinguishes them at all," University of Michigan paleontologist Lauren Sallan told the LAT.

In 1979, the same scientists found Bandringa fossils in a different part of the Mazon Creek and though they were also a different species. Within a year, two other long-nosed shark fossils were discovered in freshwater areas in the country. Still, Sallan believes they are all the same species.

Sharks today are known to use nurseries, but it would be highly irregular for one to live in freshwater and travel to saltwater to lay their eggs. Sallan and her colleagues believe the Bandringa shark did in fact practice this strange breeding pattern.

"Almost all sharks and their relatives today use nursery waters," Sallan said. "They usually use an environment very near the shore because the shallow area protects the juveniles from other sharks that may be too big to enter them."

According to a press release, no adult fossils of the Bandringa have been discovered in the Mazon Creek, but Sallan was excited to report the latest finding.

"This is the first fossil evidence for a shark nursery that's based on both egg cases and the babies themselves," Sallan said. "It's also the earliest evidence for segregation, meaning that juveniles and adults were living in different locations, which implies migration into and out of these nursery waters."