Why are parrotfish teeth tough enough to bite stony corals?

Parrotfish feed by biting stony corals so they need highly stiff, hard, fracture-tough and abrasion-resistant teeth. New chemical analyses, nano-indentation tests and polarization-dependent imaging contrast mapping experiments by a team of researchers in the US and Singapore has now revealed that they indeed have all these properties. ………

http://nanotechweb.org/cws/article/tech/70376