Petalodontiformes

Petalodontiformes ("thin-plate teeth") is an extinct order of marine cartilaginous fish related to 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. All fossils range from the Carboniferous to the Permian, where they are presumed to have died out during the Permian/Triassic extinction event.