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Lion-size otters prowled Ethiopia 3 million years ago

An illustration of the extinct giant otter called Enhydriodon omoensis. (Image credit: Sabine Riffaut/PALEVOPRIM/Université de Poitiers/CNRS)
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The fossilized remains of a gigantic, lion-size otter that lived alongside early humans have been unearthed in Ethiopia, a new study finds. 

The species, named Enhydriodon omoensis, lived about 3.5 million to 2.5 million years ago and co-existed with a group of extinct human relatives known as australopithecines, bipedal hominids that lived from 4.2 million to about 2 million years ago. E. omoensis was colossal compared with its cute contemporary counterparts, and the study authors estimated that it weighed more than 440 pounds (200 kilograms). 

E. omoensis may have eaten terrestrial and aquatic prey, either by hunting or scavenging, but the researchers think it spent its days on land, rather than in water. 

"The peculiar thing, in addition to its massive size, is that [isotopes] in its teeth suggest it was not aquatic, like all modern otters," study co-author Kevin Uno, a geochemist at Columbia University's Columbia Climate School in New York, said in a statement (opens in new tab). "We found it had a diet of terrestrial animals, also differing from modern otters."

Related: Mammals ballooned in size after the dinosaurs went extinct. Here's how they did it.

Researchers named the new species E. omoensis after the Lower Omo Valley in southwestern Ethiopia where it was discovered. They estimated its weight based on teeth and femur fossils. The researchers also measured the ratios of isotopes — variations of an element with differing numbers of neutrons — of stable oxygen and carbon in tooth enamel, as oxygen values can indicate how dependent a species was on water. 

Scientists previously thought that the Enhydriodon genus was semiaquatic, feeding on animals such as mollusks and turtles. However, the researchers found that the isotope values in E. omoensis teeth more closely matched those in fossil teeth of terrestrial mammals, such as big cats and hyenas, in the same rock deposits. 

E. omoensis is one of several gigantic otter species that lived across Eurasia and Africa up until about 2 million years ago. For example, Enhydriodon dikikae, also from Ethiopia, may have weighed 440 pounds, according to a 2011 study published in the Journal of Vertebrate Paleontology (opens in new tab). The authors of the 2011 paper wrote that E. dikikae's size was "more suggestive of a bear than of a modern otter."

The new study likens the size of these gigantic otters to lions (Panthera leo), which can measure up to 10 feet (3 meters) long and weigh 330 to 550 pounds (150 to 250 kg). The massive, extinct otters of Ethiopia would have dwarfed the otters living in North American rivers today, which typically measure up to 4 feet (1.2 m) long and weigh no more than 30 pounds (14 kg), according to the National Wildlife Federation (opens in new tab).

The biggest of all modern otters are South America's giant otters (Pteronura brasiliensis), and northern sea otters (Enhydra lutris kenyoni) from the coastal waters of southern Alaska, British Columbia and Washington. Giant otters are longer and can grow to be 6 feet (1.8 m) long, on average, and weigh up to 70 pounds (32 kg), according to Zoo Atlanta (opens in new tab). Northern sea otters can measure up to 5 feet (1.5 m) long, but they're heavier than their South American cousins and can weigh more than 100 pounds (45 kg), according to the Alaska Department of Fish and Game (opens in new tab).  

The study was published online Sept. 5 in the French journal Comptes Rendus Palevol (opens in new tab)

Originally published on Live Science.

Patrick Pester
Staff Writer

Patrick Pester is a staff writer for Live Science. His background is in wildlife conservation and he has worked with endangered species around the world. Patrick holds a master's degree in international journalism from Cardiff University in the U.K.