The fossil of an otter as big as a wolf has been discovered by scientists in south-west China.
It's thought it roamed around the warm, humid wetlands more than six million years ago.
Named Siamogale melilutra, the huge otter would have weighed around 110lb (50kg) and been up to two metres in length.
That's far bigger than even the largest otters alive today, researchers said.
The South American giant river otter for example weighs up to about 70lb (32 kg).
"Siamogale melilutra reminds us, I think, of the diversity of life in the past and how many more questions there are still to answer," said Denise Su, Cleveland Museum of Natural History curator of paleobotany and paleoecology.
"Who would have imagined a wolf-size otter?"
The earliest known otter lived about 18 million years ago.
Fossils are rare and scattered across the globe, making the study of otter evolution more challenging.
This fossil suggests the otter would have had strong jaws an enlarged cheek teeth.
"I think it used its powerful jaws to crush hard clams for food, somewhat like modern sea otters, although the latter use stone tools to smash shells," said Xiaoming Wang, head of vertebrate paleontology at the Natural History Museum of Los Angeles County.
"If Siamogale melilutra was not smart enough to figure out tools, perhaps the only option left was to develop more powerful jaws by increasing body size."
The fossils were found in China's Yunnan Province.
An almost complete cranium and lower jaw, teeth and limb bones were among the finds.
Although the skill had long been crushed during the fossilisation process, experts were able to reconstruct it digitally.
It revealed the animal had otter-like and badger-like qualities.
The same region has yielded a variety of other fossils, including an important ape skull, along with elephants, beavers, deer, crocodiles, swans and ducks.