Simplify the following text for a Grade 5 native English-speaking person.
Original: Pakicetus is a genus of extinct terrestrial carnivorous mammal of the family Pakicetidae which was endemic to Pakistan from the Eocene ( 55.8 Â 0.2 â '' 40 Â 0.1 Ma ) . Pakicetus existed for approximately .
Simplified: Pakicetus is a genus of extinct cetaceans found in the early Eocene ( 55.8 Â 0.2 - 33.9 Â 0.1 Ma ) of Pakistan , hence their name .