A mystery mammal with sharp digging claws has shed new light on the animals that walked the earth after dinosaurs.
Ancient Mongolian rocks have produced a fossil of Ernanodon antelios from 57 million years ago.
The almost complete fossil skeleton could fill in important gaps about the life of the first mammals.
A study of the bones, published in the Journal of Vertebrate Paleontology, shows that Ernanodon was built for digging, with strong arms and large claws.
The fossil skeleton show the creature may have been part of the pangolin family
Experts believe it may have been a very distant relative of present-day pangolins, or "scaly anteaters".
The fossil remains were found in rocks deposited in Naran Bulak years ago during a period known as the Palaeocene Epoch.
Scientists made detailed comparisons between the bones of Ernanodon and those of modern mammals. The animals is particular interesting to scientists because it is one of the few fossils that have a full skeleton (post-cranial.)
A photo of skeletons of Chinese pangolin (Manis pentadactyla) (top) and Ernanodon antelios.
Lead researcher Dr Peter Kondrashov, a bone specialist from Kirksville College of Osteopathic Medicine in Missouri, US, said: "Only a handful of Asian Palaeocene mammals are known by their post-cranial skeleton, which makes Ernanodon a unique source of very important information about its habits, lifestyle and affinities."
An earlier damaged Ernanodon specimen discovered by Soviet scientists in 1979 remained unstudied for more than 30 years and raised more questions than answers.
The animal's large claws and unusual teeth have led to disagreements about its evolutionary links.
Some scientists have believed the creature was an ancient relative of modern armadillos and anteaters. Others suspected it was more closely related to pangolins.
The new research confirms that it represents a very early side branch of the pangolin family tree.