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Ancient sharks reared young in prehistoric river-delta nursery

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Posted January 8, 2014
Ancient sharks reared young in prehistoric river-delta nursery
An artist’s rendering of Bandringa, a 310 million-year-old shark originally found in fossil deposits from Mazon Creek, Illinois. University of Michigan paleontologist Lauren Sallan and a colleague say this bottom-feeding predator migrated to the ocean to spawn in shallow coastal waters and left behind fossil evidence of one of the earliest known shark nurseries. Credit: John Megahan, University of Michigan.
Like salmon in reverse, long-snouted Bandringa sharks migrated downstream from freshwater swamps to a tropical coastline to spawn 310 million years ago, leaving behind fossil evidence of one of the earliest known shark nurseries.

That’s the surprising conclusion of University of Michigan paleontologist Lauren Sallan and a University of Chicago colleague, who reanalyzed all known specimens of Bandringa, a bottom-feeding predator that lived in an ancient river delta system that spanned what is today the Upper Midwest.

The new findings, scheduled for online publication Jan. 7 in the Journal of Vertebrate Paleontology, mark the earliest known example of shark migration—a behavior that persists today among species such as tiger sharks in Hawaii.

The Bandringa fossils, as reinterpreted by Sallan and Michael Coates, also reveal the only known example of a freshwater to saltwater shark migration, as well as the earliest example of a shark nursery where fossilized egg cases and juvenile sharks were preserved in the same sediments.

Read more at: Phys.org

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