Researchers have unearth fossil molar belonging to a hippopotamus root in Kenya . Thefindings , published inNature Communicationsthis week , suggests that hippo ancestors were the very first large mammals to arrive in Africa , some 30 million years ago from Eurasia . Not lions , not rhinoceros , not giraffes .
Based on genetic data , Hippo Regius and cetaceans ( whales , dolphin , and friends ) are more closely related than they are to pig and ruminants like moo-cow . They mold an exclusive group with one common ancestor believe to be a member of an extinct semi - aquatic , hippo - like group called the anthracotheres . And while we have striking fossils documenting whale evolution ( such aswhale ancestor that looked like hyaena ) , the ancestry of hippos are far more mysterious . Gaps in the fossil record have made it gruelling to realise the family relationship between hippos and the ancestor they partake with whales . " We know quite well the floor of whales , because plenty of multitude are looking for fossil of hulk , and we have a complete evolutionary history of them,“Fabrice Lihoreau of Université Montpellier IItells Washington Post . " But for the Hippopotamus amphibius , we only knew what was going on in the past 20 million years . Earlier than that , we could n’t recognize anything as a hippo . "
Back in 1994 , a downcast jaw from a previously unknown anthracothere was uncovered in the Lokone Hills of Kenya within Oligocene deposits date between 33.9 million and 23 million eld ago . Lihoreau and colleague go back in 2007 , and several teeth and subsequent analysis afterward , the team discovered that the anthracothere features many functionally average characteristics in hippo phylogenesis — include changes that likely top to the unique tooth of modern hippos .
" Each specie of mammal has a singular tooth morphology , very distinct from one species to another , so you may use them to chance similarities between two species,”Lihoreau articulate . “ This new metal money shows features very distinctive of hippos . " They describe itEpirigenys lokonensis . “ Epiri ” is hippopotamus in Turkana , Kenya , and “ genys ” is a play on ancient Hellenic words for origin , source , line , and for jaws .
Here ’s an illustration of the evolutionary transition of the upper molar from an anthracothere ( left),Epirigenys(middle ) , and a primitive hippo ( right ) . Black circles are the cusps ( chief relief of the tooth aerofoil ) , black line are the crest , and enamel isle are in orangeness .
Epirigenyswas the most abundant large mammalian at Lokone . At about 100 kilograms ( 220 lbs ) , they were much smaller than today ’s hippopotamus . " They are slender hippos , very thin hippos,“Lihoreau tells Live Science . moreover , this raw genus and metal money pushes back the evolutionary history of hippopotamids in Africa to the Paleogene , which ended around 23 million class ago . The oeuvre adds modern Hippo to the long - standing record of animal native to the continent . liken to safari favorites like Leo the Lion and antelopes , “ this is really an African mammal,”he tally .
Below are the simplify phylogenetic relationships between hippos , anthracotheres , and cetaceans , as well as the billet ofEpirigenys :
image : Fabrice Lihoreau / LPRP
