A WOLF-SIZED otter weighing close to eight stones once roamed the Earth’s ancient swamps, a study has found.

The ancient species was almost as twice as large of present-day otters and had features similar to a badger.

It also had powerful jaws to crunch large shellfish and freshwater molluscs which would have been their main food.

The otter, named Siamogale melilutra, lived some six million years ago and belongs to an ancient lineage of extinct otters, which goes back at least 18 million years.

Previously the only examples were isolated teeth recovered from Thailand until paleontologists found more fossilised remains at Shuitangba in the Yunnan Province, Southwestern China.

Scans revealed a cranium, mandible, dentition and various skeletal elements that shed light on the evolution of the fossil genus of the otter family.

Curator and head of paleobotany and paleoecology Dr Denise Su at the Cleveland Museum of Natural History said: “Otters are semi-aquatic predators in the family Mustelidae. “Modern otters have a worldwide distribution but their fossil record is poor, often consisting of fragmentary jaws and teeth.

“Multiple lineages have developed bunodont dentitions with enlargements of molars, usually for cracking molluscs or other hard foods.

“Some lineages have evolved badger-like teeth and, as a result, were often confused with melines (Old World badger clade).”

“From the vegetation and other animal groups found at Shuitangba, we know that it was a swampy, shallow lake with quite dense vegetation. While the cranium is incredibly complete, it was flattened during the fossilisation process.

“The bones were so delicate that we could not physically restore the cranium. Instead, we CT-scanned the specimen and virtually reconstructed it in a computer,”

The CT scans revealed a combination of otter-like and badger-like cranial and dental features.

Lead author, curator and head of vertebrate palaeontology Dr Xiaoming Wang at the Natural History Museum of Los Angeles County said: “Multiple otter lineages have low-crowned, bunodont teeth, leading us to ask the question if this was inherited from a common ancestor or if this was convergent evolution based on common dietary behaviours across different species“The discovery of the otter helps solve some questions about otter relationships, but has opened the door to new questions, for instance, why was it so large, how did it crack open mollusks and shellfish for food, and how did it move in the water and on land?”

The study was published in the Journal of Systematic Paleontology,