The six-foot-long babies of the world's biggest shark species, Carcharocles megalodon, frolicked in the warm shallow waters of an ancient shark nursery in what is now Panama, report paleontologists working at the Smithsonian Tropical Research Institute and the University of Florida.

Paleontologists from the Smithsonian and the University of Florida collected more than 400 fossil shark teeth from Panama´s 10-million-year-old Gatun Formation as part of ongoing work to reveal the origins of this narrow land-bridge that rose to connect North and South America about 3 million years ago. "The 28 teeth that we identified as C. megalodon were mostly from neonates and juveniles," said Pimiento. Researchers used reference collections at the Smithsonian's National Museum of Natural History and the Florida Museum of Natural History to characterize the teeth.

The team discarded several other explanations for the concentration of small teeth at the site. Before their discovery in Panama, two other fossil beds have been proposed as paleo-shark nurseries: the Williamsburg Formation from the Paleocene and the Oligocene Chandler Bridge Formation, both in the U.S. state of South Carolina.