This is a large mako with unique coloring on the blade, it has been set in a fork by a local artist and makes a stunning necklace.
The ancestor of the modern day mako shark, the Isurus hastalis or prehistoric mako shark is believed to have reached up to 30 feet long and would have been a fierce predator in the ancient oceans.
The ancient mako would have lived during the era of the megalodon shark around the Miocene to Pliocene era which means this fossil is between 3 and 16 million years old. It is thought that the ancient mako would have competed with smaller and mid size megalodons for food as well as eaten some of the same whales and ancient manatees.
The video below shows shark teeth being found in a dark water river. The tooth above is not in this video but this gives you an idea of how I find these teeth.
Fossilized Mako Shark Teeth and Megalodon Teeth for sale at www.darkwatermegs.com