By: Jason Prater

 What environmental factors are responsible for driving this transition?  Evolution of whale hearing?

 Whales, dolphins, and porpoises  Characteristics:  Obligate aquatic species  Flippers  Fluke  Vestigial hind limbs

 Artiodactyls

 Indohyus  Found in India  Small deer-like  Wading mammal

 Cenozoic Cooling  Upwelling of nutrients  Antarctic Circumpolar Current  Flows west to east around Antarctica  Nutrient exchange between Atlantic, Pacific, and Indian Ocean.

 Building of cell walls, or frustules, in diatoms  Increased diatom diversity in Cenozoic Era  Diatoms  Unicellular  Producers  One of the Most common types of phytoplankton  Eaten by Krill  Krill then eaten by whales  Short food chain (efficient in supporting apex predator)

 Evolved very quickly  Pakicetids (basal cetacean group)  Similar to land mammals  External auditory meatus  tympanic membrane  middle ear ossicles  inner ear fluid  Fails under water.

 Remingtonocetids and Protocetids  Combination of pakicetids and modern odontocetes  Sound transmitted to middle ear by large mandibular fat pad  Presence of external auditory meatus  But poor reception of airborne sound  Basilosauroids  Addition of air-filled sinuses between ear and skull  Still contained external auditory meatus even though they were obligate marine animals.  Modern Odontocetes  Loss of external auditory meatus

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