Although hippos and whales are both known as water-loving animals, they are significantly different from each other. For one, hippos basically live in African lakes while whales live in the world's ocean. A DNA analysis, however, reveals that despite the difference between these two species, both have a common ancestor.
In a new study published in the journal Nature Communications on Feb. 24, Fabrice Lihoreau, a paleontologist from the University of Montpellier in France, and colleagues reported the discovery of a new species that links the hippo with its family tree.
The species, known as Epirigenys lokonensis weighed about 100 kilograms and was about the size of a sheep, or about 20 percent of the size of the common hippopotamus that exists today.
The fossil remains of this creature was found at the Lokone Hills of Kenya with its first molar being discovered by an expedition led by Meave Leakey in 1994. Lihoreau and his team were looking for the hippo ancestor with its morphology in mind and found that the fossil was exactly what they were looking for.
The ancient creature, which spends most of its time in the water, was a member of the anthracothere, a family of animals that is now extinct and which scientists have already associated to a common ancestor of whales, dolphins, swine, cows and goats.
"We filled a gap in the evolutionary history of the hippo, bringing us closer to the point of divergence from their modern-day sister group of cetaceans," Lihoreau said.
Dental analysis has revealed that the E. lokonensis and the hippo originated from an anthracothere forefather that migrated from Asia to Africa some 35 million years earlier and since Africa was then a water-surrounded island, this ancient animal likely swam its way.
The researchers have proposed that the hippos were likely among the first big mammals that colonized the African continent with the large animal emerging in the region long before any of the other large carnivores, giraffes and bovines did about 18 million years ago. The paper thus suggests that the modern day hippo evolved in Africa, where it is truly endemic.
"Here we describe a new anthracothere from Lokone (Kenya) that unambiguously roots the Hippopotamidae into a well-identified group of bothriodontines, the first large mammals to invade Africa. The hippos are deeply anchored into the African Paleogene," the researchers wrote in their study.
