How are cetaceans like other mammals?

Mammals are defined by the ability to produce milk to feed their young.  Mammals also have a few other unique characteristics, including having hair on their bodies at some point in their lives, a diaphragm, three bones in their middle ear, and a unique jaw bone.  Cetaceans fit this physiology.  They nurse their young, give birth to live young, have hair (in very small amounts), and breathe air like land mammals.  Cetaceans, whose front appendages evolved into flippers, even have hind appendages that are so small they do not protrude from their bodies as “legs.”