Cetaceans are warm blooded, air breathing mammals .
Just like land-dwelling mammals they give birth to live young and provide milk for nourishment, and unlike other mammals, cetaceans carry out their entire lives in a water environment. Within this order, modern cetaceans are divided into two suborders that can be distinguished by the type of feeding equipment found in the mouth. These primitive cetaceans became extinct approximately 16 million years ago. There were three recognised families, however some taxonomists now suggest there are four. The family Balaenopteridae contains the six species of rorqual whales such as the Blue Whale, Humpback Whale and other similarly shaped whales.