Huge otter fossils found in China

WASHINGTON DC // Scientists have unearthed fossils of an otter as big as a wolf that frolicked in rivers and lakes in a lush, warm and humid wetlands region in south-west China about 6.2 million years ago.

The outsized otter, called Siamogale melilutra, weighed about 50 kilograms and measured up to 2 metres long, making it bigger than any of its cousins alive today, researchers said.

“Siamogale melilutra reminds us, I think, of the diversity of life in the past and how many more questions there are still to answer. Who would have imagined a wolf-size otter?” said Denise Su, curator of paleobotany and paleoecology at Cleveland Museum of Natural History. The animal had enlarged cheek teeth and strong jaws that appear to have been used for crunching hard objects, perhaps large shellfish and fresh- water mollusks, and was capable of swimming in shallow, swampy waters.

“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 Wang Xiaoming, head of vertebrate palaeontology 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, found in Yunnan province, include a largely complete cranium and lower jaw, various teeth and limb bones.

The skull was crushed aeons ago during the fossilisation process. Researchers used scanning to digitally reconstruct it, to find that it had a mix of otter- like and badger-like skull and dental traits.

There was great interest in the fossil site because an important prehistoric ape skull previously had been unearthed there. Others fossils found included elephant, rhino, tapir, deer, beaver, crocodile and water birds including swans and cranes.

The largest otter alive today is the South American giant river otter, weighing up to about 32kg. Otters belong to a mammalian family including the weasel, badger, marten and mink. The earliest-known otter lived about 18 million years ago. But otter evolution is not well understood, with fossils rare and scattered around the world.

Siamogale melilutra may not be the largest otter as the fossil of another found in Africa may be bigger.

The research was published in the Journal of Systematic Palaeontology.