The recently discovered teeth of the now-extinct sand tiger sharks are helping scientists solve the mystery of why the earth began shifting from a greenhouse climate, about 50 million years ago, towards today’s icehouse conditions.
These sharks (Striatolamia macrota) were hunted tens of millions of years ago in the waters off the Antarctic Peninsula. Their teeth have been well preserved on Seymour Island near the tip of the peninsula. Sharks shed thousands of teeth and grow new ones. The gathered evidence proves the temperatures recorded in the shark teeth are some of the warmest for these waters with high atmospheric carbon dioxide concentrations.
Theories and geological evidence show the Drake Passage waters that flow from South America and the Antarctic Peninsula and the Tasman Gateway between Australia and East Antarctica had widened and deepened when the earth’s tectonic plates moved. This resulted in waters of the major oceans coming together and today, the current that flows around Antarctica traps the cold waters in the Southern Ocean ensuring Antarctica remains cold and frozen.
Sora Kim, Assistant Professor of Paleoecology, University of California, Merced, and team studied 400 teeth from Seymour Island. The teeth examined were from all ages of shark living between 45 million to 37 million years ago. Results revealed some teeth were larger than today’s sand tiger shark which grows 10 feet long. Also, the water temperatures were warmer than what has been generally understood.
Sharks tend to migrate between summer and winter tracking warm waters. It is possible that these sand tiger sharks millions of years ago too had migrated from the cool Antarctic waters to warmer waters suggesting they survived a range of environments. Can today’s sand tiger sharks survive the faster and warmer waters due to climate change now remains to be seen.