 Odontocetes , such as the sperm whale , possess teeth with cementum cells overlying dentine cells . Unlike human teeth , which are composed mostly of enamel on the portion of the tooth outside of the gum , whale teeth have cementum outside the gum . Only in larger whales , where the cementum is worn away on the tip of the tooth , does enamel show . Mysticetes have large whalebone , as opposed to teeth , made of keratin . Mysticetes have two blowholes , whereas Odontocetes contain only one . 
