Abstract
Cetaceans are aquatic mammals of order Artiodactyla, whose earliest fossil is a terrestrial mammal from the early Eocene (~ 54 Mya). This clade comprises stem cetaceans (or 'archaeocetes'), as well as the extant taxa in the suborders Odontoceti (c. 78 species) and Mysticeti (c. 15 species). Cetaceans present profound cranial changes related to the 'telescoped' skull, remarkable directiona…