Scientists recently unearthed several teeth of anthracotheres, an ancestor of the hippopotamus that lived approximately 40 million years ago. The discovery was imperative in better understanding this extinct species, which is described as diminutive hippos about the size of a sheep. Interestingly enough, according to Live Science, anthracotheres are also related to whales and dolphins, shedding new light on similarities between whales and hippos. The fossils also suggest that hippos evolved in Africa and therefore are truly indigenous to the continent.
Digging up teeth
French paleontologists were studying the jaw of an anthracothere in Nairobi, Kenya, and decided to travel where the fossil was first found. The area, known as Lokone Hill, is rich in rock samples that are about 28 million years old, and the ground is a hotspot for ancient animal fossils. The paleontologists found several anthracothere teeth, including molars. Scientists then used the distinct tooth samples to reveal the dental evolution from anthracotheres to hippos.
Mammals in general have unique dental features, and hippos in particular have a specific three-leafed pattern, according to Live Science. Using samples dating to 10 million, 28 million and 40 million years ago, scientists were able to reveal similarities in the teeth of a middle ancestor known as Epirigenys lokonensis and modern-day hippopotamuses.
The scientists' discovery and complementary research was published on Feb. 24, 2015, in the online journal Nature Communications.
Relation to whales
Researchers believe an anthracothere resembled a slender hippo that weighed about 220 pounds. According to the Washington Post, DNA suggests that hippos and whales have been related for some time, but the new fossil findings provide more substantial proof.
"We know quite well the story of whales, because lots of people are looking for fossils of whales, and we have a complete evolutionary history of them," Fabrice Lihoreau, lead author of the study told the Washington Post.
On the other hand, the lack of hippo fossil records has left scientists wondering where their exact origins are located. Ideally, researchers will be able to uncover more fossils in the future to strengthen this connection, but teeth are often one of the last parts of the skeleton to remain. Lihoreau is optimistic that the dental samples will confirm the relation:
"Each species of mammal has a unique tooth morphology, very distinct from one species to another, so you can use them to find similarities between two species. This new species shows features very typical of hippos."