Recent analysis of these hippopotamus fossils reveals that it is in fact related to the cetaceans, which is the group that includes animals like whales, porpoises and dolphins. This means that these are the ancient animal’s closest living relatives.
Fabrice Lihoreau, paleontologist at the University of Montpellier in France, explains that until now, the origins of the hippopotamus have been an enigma for researchers everywhere.
According to Lihoreau, the hippos evolved from the anthracotheres, which was a group of semi-aquatic herbivorous mammals that had even-toed hooves.
Until this recent discovery, the oldest known fossil belonging to a hippopotamus ancestor dated back approximately 20 million years ago. Also, the researchers have cetacean remains that are more than 53 million years old.
It was previous thought that the hippo was a distant relative of the pig, which belongs to the Suidae family. These assumptions were made based on previous paleontological findings, but later DNA analysis suggested that these animals were actually related to the whales.
However, the scientists are still puzzled by the giant gap between the cetaceans and the hippopotamus in the fossil record.
According to Lihoreau, this means that the hippo ancestors were never found or were not recognized among the fossils the experts have been studying.
But a 28 million year old fossil discovered recently in Kenya provides an important missing piece to the puzzle that is the origin of hippos.
The fossils belong to an animal named Epirigenys lokonensis, that was the size of a sheep and weighed approximately 100 kg, a lot less than what a modern-day hippo weighs. The experts believe the ancient hippo may have spent a lot of its time in the water.
This animal was not a direct relative of today’s hippopotamus but belonged to a side branch.
Dental analysis reveals that the Epirigenys lokonensis and the modern hippo evolved from the anthracothere, which migrated from Asia to Africa more than 35 million years ago.
These findings were published in the journal Nature Communications.
Image Source: hippoworlds