megalodontid

Noun

 * 1)  Any of the extinct bivalves in the family.
 * 1)  Any of the extinct bivalves in the family.

Usage notes
The family of wood wasps referred to by the first sense was given the name Megalodontidae in 1897- which was against the rules because the bivalves had been already been given that name in 1853. The wood wasp family was renamed to in 1996, but "megalodontid" for the century up to then often refers to wood wasps.