Pakicetus is a genus of extinct cetaceans found in the early Eocene of Pakistan 55.8 ± 0.2 - 33.9 ± 0.1 million years ago (mya). The strata where the fossils were found was then on the coast of the Tethys Sea.
Temporal range: early Eocene, 49–33.9 mya
The first fossil, a lone skull, was thought to be a mesonychid, but Gingerich and Russell recognized it as an early cetacean. It had characteristics of the inner ear which are found only in cetaceans: the large auditory bulla is formed from the ectotympanic bone only. This suggests that it is a transitional species between extinct land mammals and modern cetaceans.
Complete skeletons were discovered in 2001. Pakicetus was mainly a land animal, about the size of a wolf, and very similar in form to the related mesonychids.
- Gingerich, Philip D. & Russell, Donald E. 1981. Pakicetus inachus, a new Archaeocete (Mammalia, Cetacea) from the early-middle Eocene Kuldana Formation of Kohat (Pakistan). Contributions from the Museum of Paleontology, The Museum of Michigan. 25 (11): 235–246.
- Gingerich, Philip D. et al 1983. Origin of whales in epicontinental remnant seas: new evidence from the early Eocene of Pakistan. Science. 220 (4595): 403–6. . PMID 17831411.