What is "cretolamna"

Cretolamna is a genus of extinct mackerel shark that belonged to either the family Cretoxyrhinidae or Otodontidae.

These sharks lived during from the Barremian of the Cretaceous period to the Mid Miocene epoch, approximately from 130.0 to 13.65 million years ago. It is considered by many to be the ancestor of many of the famous shark genera, such as the mako, great white, Angustidens, and Megalodon sharks.