pet·al·o·don·ti·dae \ˌ ̷ ̷ ̷ ̷ ̷ ̷ˈdäntəˌdē\noun plural Usage: capitalized Etymology: New Latin, from Petalodont-, Petalodus, type genus + -idae : a family of Carboniferous and Permian elasmobranchs (subclass Holocephali) related to the rays and having peculiar flattened petaloid teeth and greatly enlarged pectoral fins — see petalodus