Author: Ed Wong
Source: Nature 
August 13, 2012
"For centuries, the people of the Gilbert Islands in the central Pacific Ocean have crafted weapons from shark teeth. Joshua Drew, a conservation biologist at Columbia University in New York, has used these teeth to show that the waters around the islands — part of the Republic of Kiribati — were once home to three species of shark that no longer live in the area.
“This is shadow biodiversity,” said Drew, presenting his results at the 2012 Ecological Society of America Annual Meeting in Portland, Oregon, last week. “Three sharks disappeared from these reefs before we even knew that they existed there.”
Drew analysed 124 shark-tooth weapons housed in the collection of the Field Museum of Natural History in Chicago, Illinois. The artefacts included swords, tridents and a 4-metre-long lance, dating back over 120 years. All are built in the same way: the islanders drill hole in the teeth and lash them to buttresses of wood with cords made from coconut leaves. All the teeth in one weapon usually come from one species, but Drew found several blades in which the penultimate tooth belonged to a rare species of blue shark (Prionace glauca) — possibly the signature of a single artisan."
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