Sinodelphys szalayi was a nocturnal animal, active around dawn and dusk.
WASHINGTON (AP) -- The fossil of a tiny creature found in Northeast China is helping scientists determine when mammals split into different groups: those with babies that develop inside their mothers and those that raise their offspring in pouches.
The two groups make up more than 99 percent of all mammals today, and the new fossil evidence indicates the separation began in Asia about 125 million years ago.