New wolf-sized species of ancient otter discovered in China

A newly identified species of prehistoric otter weighed more than 100 pounds and was about the same size as a modern-day wolf, making it one of the largest otters ever discovered, according to research published online earlier this week by the Journal of Systematic Palaeontology.

Dubbed Siamogale melilutra, the creature lived more than six million years ago in the Yunnan Province in China and was “two to three times larger than any modern otter species,” Denise Su, curator and chief of paleobotany and paleoecology at the Cleveland Museum of Natural History and co-author of the new study, said Monday in an interview with NPR.

Dr. Su and her colleague Dr. Xiamong Wang, curator and head of vertebrate paleontology at the Natural History Museum of Los Angeles County, explained that Siamogale melilutra was part of a lineage of extinct otters that was previously identified only through the discovery of a few teeth belonging to a different, far older species that were previously recovered in Thailand.

With this new species, however, the study authors found a complete cranium and mandible along with other skeletal remains, which allowed made it possible for them to discern much about these creatures’ evolutionary history, functional morphology and taxonomy, they said in a statement.

“While the cranium is incredibly complete, it was flattened during the fossilization 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,” explained Dr. Su. Through those CT scans, the researchers learned that the species possessed both otter-like and badger-like features, leading to the name “melilutra” (a combination of the Latin words for otter and badger).

One mystery solved, but another puzzle remains unanswered

Among the discoveries made through the analysis of these newly discovered fossils, NPR noted, was the answer to a longstanding mystery surrounding the teeth of otters. Giant otters, they said, possessed large bunodont, or round-cusped, teeth, and researchers were unsure if these teeth had been inherited from a common ancestor or if they were the result of convergent evolution.

Based on their analysis, Dr. Su and Dr. Wang determined that these bunodont teeth had appeared independently on at least three separate occasions through the evolutionary history of otters, thus suggesting that convergent evolution caused by the creatures consuming the same kinds of foods was the most likely cause.

Professor Ji Xueping of the Yunnan Provincial Institute of Cultural Relics and Archaeology told CNN that Siamogale melilutra would have been a semi-aquatic creature that measured between 1.5 and 2.0 meters (5 and 6.5 feet) in length and would have fed on fed on large shellfish, which it would have crushed between its powerful jaws. While they have learned much about otters by studying this new specimen, they remain puzzled about the reasons why it grew so big.

“A lot of times in modern carnivores, the large size is partly due to subduing prey, so their prey is bigger and the carnivores also get bigger,” Dr. Su told NPR. But as that was not the case here, “Why did this species grow so large? How did its size affect its movement on land and in water? And most importantly, what types of advantages did its size give?” Additional research is needed before those questions can be answered.

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Image credit: Cleveland Museum of Natural History