From Chicago Tribune:

… Before the time of the dinosaurs, long-nosed Bandringa sharks were leaving their freshwater homes to lay eggs in the shallow coastal waters of a long-gone sea that stretched over most of the American Midwest, according to a new paper published in the Journal of Vertebrate Paleontology….

…

In 1969, researchers discovered beautifully preserved fossils of baby Bandringa sharks, as well as their spiral egg casings, along Mazon Creek in northeastern Illinois. The juvenile sharks, just 4 to 6 inches long, had pronounced spoon-billed snouts that stretched half as long as their bodies. At the time, scientists thought the babies might be adult specimens of a mini-shark species that they dubbed Bandringa rayi.

Ten years later, in 1979, the same scientists discovered more juvenile Bandringa shark fossils in a different part of Mazon Creek that had once been a brackish swamp. Thinking they were a new species, the scientists called them Bandringa herdinae. That same year, researchers in Pennsylvania found a 10-foot-long adult shark that also had the same long spoon-billed snout and lived in freshwater rivers. A few years later, another large adult was discovered in what was once a freshwater river in Ohio.

In a paper published online Tuesday, University of Michigan paleontologist Lauren Sallan argues that all of the sharks are members of the same species….