<p>The order Cetacea comprises two extant sub-orders and one extinct sub-order. The extant sub-orders are <span class="taxon">Mysticeti</span> (baleen whales) and <span class="taxon">Odontoceti</span> (toothed whales). Both <span class="taxon">mysticeti</span> and <span class="taxon">odontoceti</span> are thought to be descendants of archaeocetes (<span class="taxon">Archaeoceti</span>, ancient whales), an extinct sub-order. There are at least 83 living species of cetaceans, with 46 genera in 14 families. Of the two extant suborders, <span class="taxon">Odontoceti</span> is larger and more diverse, with at least 70 species, 40 genera, and 10 families. Cetaceans, along with <span class="taxon">Chiroptera</span>, are considered some of the most derived mammals on the planet. They evolved from terrestrial animals to an entirely aquatic life form that is completely separated from the land in all aspects of biology. Cetaceans live, breed, rest, and carry out all of their life functions in the water.<span> (Gingerich et al., 2001; Reeves et al., 2002; Rice, 1984)</span></p>