 Beaked whales consist of over 20 genera . Earlier variety were probably preyed upon by killer sperm whales and large sharks such as Megalodon . In 2008 , a large number of fossil ziphiids were discovered off the coast of South Africa , confirming the remaining ziphiid species might just be a remnant of a higher diversity that has since gone extinct . After studying numerous fossil skulls , researchers discovered the absence of functional maxillary teeth in all South African ziphiids , which is evidence that suction feeding had already developed in several beaked whale lineages during the Miocene . Extinct ziphiids also had robust skulls , suggesting that tusks were used for male @-@ male interactions . 
