New large docodont fossil sheds light on Jurassic mammaliaform diversity

SHENYANG -- An international team led by Chinese scientists has discovered a new docodont mammaliaform species, the largest known of its kind, in Jurassic strata dating back about 160 million years, enriching scientific understanding of Jurassic mammaliaform diversity.

The new species has been named Megacauda sungei. Its fossil specimen, discovered in Ningcheng, North China's Inner Mongolia autonomous region, measures roughly 52 centimeters in length and is estimated to have weighed around 2 kilograms, making it the largest known docodont mammaliaform. Its skull is clearly preserved, its trunk is robust, and its most striking feature is an unusually long, coiled tail.

The specimen also retains well-preserved pelvic bones, hind limbs and tail vertebrae, suggesting it was adapted for swimming. Based on its distinctive teeth, researchers believe it could have hunted small animals living in the same environment, with a lifestyle possibly similar to that of the modern platypus.

The study also sheds light on the animal's throat structure. The bones in its throat are similar to those of modern mammals, suggesting that behaviors such as swallowing, lapping and suckling may have already existed in the early ancestors of mammals, long before modern mammal groups appeared.

"Mammaliaforms from the Mesozoic are often imagined as tiny creatures under dinosaur feet, but Megacauda sungei clearly raises the size limit of this group," said Li Yikun, an associate professor at Shenyang Normal University in Northeast China.

The study was published online in the journal Nature on Oct 7.