 Fossil sperm whales differ from modern sperm whales in tooth count and the shape of the face and jaws . For example , Scaldicetus had a tapered rostrum . Genera from the Oligocene and early and middle Miocene , with the possible exception of Aulophyseter , had teeth in their upper jaws . Acrophyseter , from the late Miocene , also had teeth in both the upper and lower jaws as well as a short rostrum and an upward curving mandible ( lower jaw ) . These anatomical differences suggest that fossil species may not have necessarily been deep @-@ sea squid eaters like the modern sperm whale , but that some genera mainly ate fish . <unk> , dated from the middle to late Miocene and found in southern Italy , had teeth in both jaws and appears to have been adapted to feed on large prey , rather like the modern Orca ( Killer Whale ) . Other fossil sperm whales with adaptations similar to this are collectively known as killer sperm whales . 
