The earliest shark nursery containing fossils of both young sharks and eggs has been found at the site of a nuclear power plant in northeastern Illinois.
The nursery, once located at what is now Mazon Creek at the Braidwood Nuclear Generating Station site, dates to 310 million years ago, according to a paper published in the Journal of Vertebrate Paleontology. It used to be teeming with a long-snouted shark called Bandringa, which was one of the earliest close relatives of all modern sharks.
"At least a dozen juvenile Bandringa shark fossils -- and probably more -- have been recovered from the site," University of Michigan paleontologist Lauren Sallan, who co-authored the paper with Michael Coates, told Discovery News.
Some of the fossils are in a remarkable state of preservation.
"We even have soft body tissue from the juvenile sharks," Sallan said, adding that the tissue retains pigment that, in the future, could reveal the precise coloration of the sharks. DNA could probably not be extracted from it, though.
The paleontologists studied the fossils, along with those of 12 adult Bandringas. This shark was previously classified into two species, but the researchers determined that all of the fossils belonged to just one species. The scientists also gained a more complete picture of the extinct shark's anatomy and distinctive features.
"Bandringa had a head entirely covered in large spines, a long paddle-like rostrum (snout) with electroreceptors, and one of the earliest jaws capable of protruding and suction feeding," Sallan said.
It resembled present-day sawfish and paddlefish. The huge snout took up half of its body length. The electroreceptors on the snout helped the sharks to locate prey, which consisted of small crustaceans and other marine life.
Juveniles were 4 to 6 inches long. They grew into adults of up to 10 feet long.