jan 1, 1983 - Pakicetus inachus found with bullae

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Pakicetus inachus from the early Eocene of Pakistan is the oldest and most primitive cetacean known. The dentition resembles that of carnivorous mesonychid land mammals as well as middle Eocene cetaceans. The otic region of the cranium lacks characteristic specializations of whales necessary for efficient directional hearing under water.
Discovery of Pakicetus strengthens earlier inferences that whales originated from terrestrial carnivorous mammals and suggests that whales made a gradual transition from land to sea in the early Eocene, spending progressively more time feeding on fish.

Origin of Whales in Epicontinental Remnant Seas: New Evidence from the Early Eocene of Pakistan
BY PHILIP D. GINGERICH, NEIL A. WELLS, DONALD E. RUSSELL, S. M. IBRAHIM SHAH
SCIENCE22 APR 1983 : 403-406

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