 Although the fossil record is poor , several extinct genera have been assigned to the clade Physeteroidea , which includes the last common ancestor of the modern sperm whale , pygmy sperm whales , dwarf sperm whales , and extinct physeteroids . These fossils include Ferecetotherium , Idiorophus , Diaphorocetus , Aulophyseter , Orycterocetus , Scaldicetus , Placoziphius , Zygophyseter and Acrophyseter . Ferecetotherium , found in Azerbaijan and dated to the late Oligocene ( about 28 to 23 million years ago ) , is the most primitive fossil that has been found which possesses sperm whale @-@ specific features such as an asymmetric rostrum ( " beak " or " snout " ) . Most sperm whale fossils date from the Miocene period , 23 to 5 million years ago . Diaphorocetus , from Argentina , has been dated to the early Miocene . Fossil sperm whales from the Middle Miocene include Aulophyseter , Idiorophus and Orycterocetus , all of which were found on the west coast of the United States , and Scaldicetus , found in Europe and Japan . Orycterocetus fossils have also been found in the North Atlantic Ocean and the Mediterranean Sea , in addition to the west coast of the United States . Placoziphius , found in Europe , and Acrophyseter , from Peru , are dated to the late Miocene . 
