Petalodontidae

Petalodontidae is an extinct family of cartilaginous fish related to the modern-day chimaera, found in what is now the United States of America and Europe. With a very few exceptions, they are known entirely from teeth.
Petalodontids belong to the order Petalodontiformes, an order of prehistoric fishes. Petalodontidae is the most popular family of the Petalodontiformes. The type genus is "Petalodus".