A recent research paper written by a team of French and Kenyan paleontologists has revealed the discovery of a 28-million-year-old ancestor of the hippopotamus in the volcanic earth of Lokone, located in the Lake Turkana basin of Kenya. Forty other fossilized species of four-legged whales from the same period were also unearthed.
The discovery not only links the present-day hippopotamus to the anthracothere, an extinct species of mammals related to hippos and cetaceans (whales, dolphins etc.), but also proves that hippos and whales are the closest living cousins on Earth.
The team of researchers, headed by Jean-Renaud Boisserie, have called this new fossil species Epirigenys lokonensis, referencing the location in which the discovery was made. The Epirigenys has bridged a gap between the oldest discovered fossilized hippo, which goes back 20 million years, and the anthracothere, the oldest of which is 40 million years old and was discovered in Romania.
Currently, the oldest cetacean fossils found are 53 million years old and the new discovery would indicate that the common ancestor between hippos and whales is approximately 55 million years old.
Migration
Approximately 18 to 110 million years ago, Asia and Africa were separated by 100 km of water. During this period, rodents and monkeys crossed the sea from the north to the south, followed by mammals like lions, zebras and antelopes, the study says.
This new discovery has also managed to clarify the migratory period for the extinct anthracotheres. With the knowledge gleaned from the Epirigenys, it is now believed that the anthracotheres migrated from Asia approximately 35 million years ago, 15 million years before other animal species. This would indicate that hippos have been on the African continent much longer than originally thought.
Despite the extraordinary new information the research team has managed to extract from this discovery, the chronology completing the historical puzzle between the hippopotamus and its cetacean cousins is still partially missing. Further study into the 15-million-year gap will one day help form a clearer picture of how these mammals evolved.
