Juramaia

Juramaia is the earliest known eutherian mammal. It is a small shrew-like mammal of body length about 70100 mm. It is an extinct genus  from the Upper Jurassic deposits of western Liaoning, China. 

A nearly complete skeleton, with an incomplete skull with full dentition was found. It was collected in the Daxigou site, Jianchang, from the Tiaojishan Formation. It is dated at about 160 million years ago. Electronic supplementary material

The discovery of Juramaia provides new insight into the evolution of eutherian mammals. It shows their lineage diverged from that of the marsupials 35 million years earlier than previously thought.  Furthermore, its discovery fills gaps in the fossil record and helps to calibrate modern, DNA-based methods of dating the evolution."Fossil redefines mammal history" BBC NewsDiscovery of a 160-million-year-old fossil represents a new milestone in early mammal evolution 

The forelimb bones have climbing adaptations, so it is suggested  that the basal stock of Eutheria was arboreal.

 Related pages 
 Eomaia
 Sinodelphys

 References 

Category:Extinct mammals
Category:Fossils
Category:Jurassic