Wednesday 2 July 2014

Ancient Freshwater Sharks

Ancient Arctic Sharks Lived In Brackish Water 50 Million Years Ago
Most sharks today are strictly saltwater fish, however, a new study led by the University of Colorado Boulder and the University of Chicago reveals that this was not the case 50 million years ago. Sharks in the Arctic Ocean during this time lived in brackish water, with approximately the same amount of freshwater found in modern day Lake Ponchatrain in Louisiana.
The study, led by University of Chicago postdoctoral researcher Sora Kim, suggests that the Eocene Arctic sand tiger shark thrived in the brackish water of the western Arctic Ocean. In contrast with the Eocene Arctic sand tiger shark (part of the lamniform group of sharks that includes today’s great white, thresher and mako sharks), the modern sand shark in the Atlantic Ocean requires three times the salinity and is very intolerant of low salt levels.

Food for  thought.What if some lake creature sightings were evolved ancient freshwater sharks?


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